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Recovery Strategy for the Least Bittern (Ixobrychus exilis) in Canada [PROPOSED] – 2011
Species at Risk Act
Recovery Strategy Series
Table of Contents
- Executive Summary
- Recovery Feasibility Summary
- 1. COSEWIC Species Assessment Information
- 2. Species Status Information
- 3. Species Information
- 4. Threats
- 5. Population and Distribution Objectives
- 6. Broad Strategies and General Approaches to Meet Objectives
- 7. Critical Habitat
- 7.1 Identification of the Species’ Critical Habitat
- 7.2 Schedule of Studies to Identify Critical Habitat
- 7.3 Activities Likely to Result in the Destruction of Critical Habitat
- 8. Measuring Progress
- 9. Statement on Action Plans
- 10. References
- Appendix A: Standard Breeding Bird Atlas codes
- Appendix B: Least Bittern Critical Habitat
- Appendix C: Effects on the Environment and Other Species
Recovery Strategy for the Least Bittern (Ixobrychus exilis) in Canada [PROPOSED] – 2011.
Environment Canada. 2011. Recovery Strategy for the Least Bittern (Ixobrychus exilis) in Canada [Proposed]. Species at Risk Act Recovery Strategy Series. Environment Canada. Ottawa. v + 34 pp.
For copies of the recovery strategy, or for additional information on species at risk, including COSEWIC Status Reports, residence descriptions, action plans, and other related recovery documents, please visit the Species at Risk (SAR) Public Registry.
Cover illustration: © Benoît Jobin, Environment Canada, Canadian Wildlife Service – Québec region
Également disponible en français sous le titre :
« Programme de rétablissement du Petit Blongios (Ixobrychus exilis) au Canada [Proposition] »
© Her Majesty the Queen in Right of Canada, represented by the Minister of the Environment, 2011. All rights reserved.
Content (excluding the illustrations) may be used without permission, with appropriate credit to the source.
The federal, provincial, and territorial government signatories under the Accord for the Protection of Species at Risk (1996) agreed to establish complementary legislation and programs that provide for effective protection of species at risk throughout Canada. Under the Species at Risk Act (S.C. 2002, c.29) (SARA), the federal competent ministers are responsible for the preparation of recovery strategies for listed Extirpated, Endangered, and Threatened species and are required to report on progress within five years.
The Minister of the Environment and the Minister responsible for the Parks Canada Agency are the competent ministers for the recovery of the Least Bittern, a Threatened species listed in Schedule 1 of SARA, and have prepared this recovery strategy, as per section 37 of SARA. It has been prepared in cooperation with the Provinces of Manitoba, Ontario, New Brunswick, and Nova Scotia.
Success in the recovery of this species depends on the commitment and cooperation of many different constituencies that will be involved in implementing the directions set out in this strategy and will not be achieved by Environment Canada, the Parks Canada Agency, or any other jurisdiction alone. All Canadians are invited to join in supporting and implementing this strategy for the benefit of the Least Bittern and Canadian society as a whole.
This recovery strategy will be followed by one or more action plans that will provide information on recovery measures to be taken by Environment Canada, the Parks Canada Agency, and other jurisdictions and/or organizations involved in the conservation of the species. Implementation of this strategy is subject to appropriations, priorities, and budgetary constraints of the participating jurisdictions and organizations.
Andrew Horn (Dalhousie University) prepared the initial draft recovery strategy for the Least Bittern. Earlier drafts were reviewed by Members of the National Least Bittern Recovery Team [Vincent Carignan, Chair (Environment Canada, Canadian Wildlife Service – Québec region), Ron Bazin (Environment Canada, Canadian Wildlife Service – Prairie & Northern region), Samara Eaton (Environment Canada, Canadian Wildlife Service–Atlantic Region), Valerie Blazeski (Parks Canada Agency), Ken DeSmet (Manitoba Conservation), Laurie Maynard and Dave Moore (Environment Canada, Canadian Wildlife Service – Ontario region), Jon McCracken (Bird Studies Canada), and Eva Katic (National Capital Commission)], former members of the recovery team [Benoît Jobin (Environment Canada, Canadian Wildlife Service – Québec region), Mark McGarrigle (New Brunswick Department of Natural Resources), Todd Norris (Ontario Ministry of Natural Resources), Jennifer Stewart (Environment Canada, Canadian Wildlife Service – Atlantic region) and Gershon Rother].
Other contributors provided comments on the recovery strategy : Marie–José Ribeyron (Environment Canada, Canadian Wildlife Service – National Capital region), Karine Picard and Matthew Wild (Environment Canada, Canadian Wildlife Service – Québec region), Diane Amirault–Langlais and Paul Chamberland (Environment Canada, Canadian Wildlife Service –Atlantic region), Kari Van Allen, Angela Darwin, Angela McConnell, Barbara Slezak, Krista Holmes, Ewen Eberhardt, Jeff Robinson and Tania Morais (Environment Canada, Canadian Wildlife Service – Ontario region), David Bland, Michael Patrikeev and Stephen McCanny (Parks Canada Agency), Corina Brydar and Sandy Dobbyn (Ontario Parks), Jodi Benvenuti, Vivian Brownell, Glenn Desy, Leanne Jennings, Chris Risley, Marie–Andrée Carrière, Shaun Thompson, Don Sutherland, Lauren Trute, Doug Tozer and Allen Woodliffe (Ontario Ministry of Natural Resources).
The following individuals provided information on Least Bittern population and habitat distribution, population trends, life history, survey methods, and conservation and management: Nickolas Bartok, Heidi Bogner, Robert Bowles, Courtney Conway, Glenn Desy, Pierre Fradette, Jonathon French, Christian Friis, Stacey Hay, Gary Huschle, Rudolf Koes, Claudie Latendresse, Soch Lor, Paul Messier, Shawn Meyer, Frank Nelson, Sarah Richer, Dave Roberts, Luc Robillard, Tracy Ruta–Fuchs, François Shaffer, Peter Taylor, Guillaume Tremblay, Breeding Bird Atlas and Marsh Monitoring Program volunteers, and birders in Manitoba, Ontario, Québec and the Maritimes.
The Least Bittern (Ixobrychus exilis), North America’s smallest heron, breeds in freshwater and brackish marshes with dense, tall persistent emerging plants, interspersed with open water and occasionally clumps of vegetation. It has been listed as Threatened under Schedule 1 of the Species at Risk Act (SARA) since 2003 because of apparent historical declines throughout its range.
Canada has 2–3% of the estimated 43,000 pairs distributed throughout southern Canada (Manitoba, Ontario, Québec, New Brunswick and Nova Scotia), the United States and in countries as far south as Argentina and Brazil. Because of the species' secretive habits and the difficulties of searching its habitat, population size and trend estimates are imprecise.
Wetland loss and degradation as well as impaired water quality are believed to be the primary threats to Least Bitterns throughout their range. Other threats include regulated water levels (except for conservation purposes), invasive species, collisions (with cars and anthropogenic structures), recreational activities, and climate change.
There are unknowns regarding the feasibility of recovery of the Least Bittern. Nevertheless, in keeping with the precautionary principle, this recovery strategy has been prepared as per section 41(1) of SARA as would be done when recovery is determined to be feasible.
The population and distribution objectives for the Least Bittern are to maintain and, where possible, increase the current Canadian population size and area occupancy. Broad strategies and approaches to achieve these objectives are presented in the Strategic direction for recovery section.
Critical habitat is partially identified in this recovery strategy. It is contained within 98 breeding sites, 10 of which are located in Manitoba, 44 in Ontario, 42 in Québec and 2 in New Brunswick. A schedule of studies outlines key activities to identify additional critical habitat at breeding, foraging, post–breeding dispersal, moulting and migration stopover sites. One or more action plans will be posted on the Species at Risk Public Registry before 2016.
In considering the criteria established by Government of Canada (2009), unknowns remain as to the recovery feasibility of the Least Bittern. Nevertheless, in keeping with the precautionary principle, this recovery strategy has been prepared as per section 41(1) of SARA as would be done when recovery is determined to be feasible. This recovery strategy addresses the unknowns surrounding the feasibility of recovery.
- Individuals of the wildlife species that are capable of reproduction are available now or in the foreseeable future to sustain the population or improve its abundance.
Yes. Breeding individuals are currently available and distributed throughout the Canadian range as well as in the United States.
- Sufficient suitable habitat is available to support the species or could be made available through habitat management or restoration.
Yes. Sufficient wetland habitat is available to support the species at its current level. Unoccupied suitable habitat is also available and additional wetlands could become suitable after restoration efforts or wetland creation.
- The primary threats to the species or its habitat (including threats outside Canada) can be avoided or mitigated.
Unknown. The main threats to the species and its breeding habitat, and methods to avoid or mitigate them are known. However, some of these methods need to be refined and tested in Canada. Furthermore, foraging, post–breeding dispersal, moulting and migration stopover sites have yet to be identified and the threats to those sites will need to be specified.
- Recovery techniques exist to achieve the population and distribution objectives or can be expected to be developed within a reasonable timeframe.
Unknown. Habitat stewardship, wetland restoration techniques as well as wetland creation and management have proven to be effective for this species although specific management prescriptions need to be developed. Mitigating other threats, such as off–site effects on wetland habitat quality, however, will be a continuing challenge.
1. COSEWIC Species Assessment Information
Date of Assessment: April 2009
Common Name (population): Least Bittern
Scientific Name: Ixobrychus exilis
COSEWIC Status: Threatened
Reason for designation: This diminutive member of the heron family has a preference for nesting near pools of open water in relatively large marshes that are dominated by cattail and other robust emergent plants. Its breeding range extends from southeastern Canada through much of the eastern U.S. Information on the population size and exact distribution of this secretive species is somewhat limited. Nevertheless, the best available evidence indicates that the population is small (about 3000 individuals) and declining (> 30% in the last 10 years), largely owing to the loss and degradation of high–quality marsh habitats across its range.
Canadian Occurrence: Manitoba, Ontario, Québec, New Brunswick and Nova Scotia
COSEWIC Status History: Designated Special Concern in April 1988. Status re–examined and confirmed in April 1999. Status re–examined and designated Threatened in November 2001 and April 2009.
Canada has 2–3% of the estimated 43,000 pairs of Least Bitterns in North America (Delany and Scott, 2006). The species has been listed as Threatened under Schedule 1 of the Species at Risk Act (S.C. 2002, c. 29) since 2003. In Québec, it has been listed as Vulnerable under the Act respecting threatened or vulnerable species (R.S.Q., c. E–12.01) since 2009. In Ontario, it has been listed as Threatened on the Species at risk in Ontario list since 2004 and regulated under the Endangered Species Act, 2007 (S.O. 2007, C. 6) since 2008. As of December 2011, the species had not been listed in Manitoba, New Brunswick or Nova Scotia.
The International Union for the Conservation of Nature ranks the global population of this species as “Least Concern” (BirdLife International, 2009). NatureServe (2010) conservation ranks for Canada and the United States vary widely as shown in Table 1.
|Global Rank (G)||National Rank (N)||Sub–National Rank (S)1,2|
|N3B – Canada|
N5B, N5N – United States
(secure during breeding and nonbreeding)
|Manitoba (S2S3B) ; New Brunswick (S2B) ; Nova Scotia (S1B); Ontario (S4B); Quebec (S2S3B)|
SH (Utah) ; S1 (California, Delaware, District of Columbia, Kentucky, Massachusetts, New Hampshire, Oregon, Pennsylvania, West Virginia) ; S2 (Arkansas, Colorado, Connecticut, Illinois, Kansas, Maine, Maryland, Michigan, Nevada, Ohio, Rhode Island, South Dakota, Tennessee, Vermont) ; S3 (Arizona, Indiana, Iowa, Mississippi, Missouri, New Jersey, New Mexico, New York, North Carolina, Virginia, Wisconsin)
1 1: Critically Imperiled; 2: Imperiled; 3: Vulnerable; 4: Apparently Secure; 5: Secure; H: possibly extirpated; B: Breeding.
2 In most states along the Gulf coast (e.g., Texas, Louisiana, Florida), where it is resident year–round, it is not listed, and has been recently removed from the federal list of "Species of Management Concern" (USFWS, 2002).
Measuring about 30 cm and weighing 80 g, the Least Bittern is North America’s smallest heron (Kushlan and Hancock, 2005). It is brown and buffy overall, with broad buff streaks on its white underside, and a contrasting back and crown that is glossy black in adult males but lighter in females and juveniles. Buff wing patches, which are especially obvious when the bird flushes, distinguish this species from all other marsh birds. When disturbed, the bird uses a rail–like “rick–rick–rick–rick” or an advertisement call that consists of repeated coos “coo–coo–coo” (Sibley, 2000). Further details are provided in the COSEWIC (2009) status report.
Least Bitterns breed from southern Canada to South America, including the Caribbean, and winter from California to Florida south to Mexico and Latin America, with resident populations in river valleys and coastal areas farther south to northern Argentina and southern Brazil (COSEWIC, 2009; Poole et al., 2009). Isolated migrant populations breed in Oregon, California, and New Mexico, and formerly in Utah (Figure 1).
The distribution of the species during the adult moulting phase needs further study but the timing of this phase (mid–September to mid–December) suggests it mostly takes place during migration (Poole et al., 2009). The migratory routes of Least Bitterns are unknown, but it is presumed that they migrate in a broad front that is locally funneled by north–south oriented peninsulas and coasts such as found in the closely related Little Bittern (Ixobrychus minutus) of Eurasia (Nankinov, 1999). The winter habitat of Least Bitterns is also poorly known, although the species is presumed to occupy brackish and saline swamps and marshes of the southern United States and Central America (Poole et al., 2009).
In Canada, Least Bitterns breed in Manitoba, Ontario, Québec, New Brunswick (and possibly Nova Scotia) where they generally occur south of the Canadian Shield (COSEWIC, 2009; Figure 2). They have been reported as vagrants in other provinces. The Canadian Least Bittern breeding population is estimated at 1500 pairs (between 1000 and 2800; COSEWIC, 2009; Table 2). This figure comes from various sources including breeding bird atlases, targeted field work and citizen–driven monitoring programs (e.g. Marsh Monitoring Program) and it does not take into account immatures, sub–adults and non–breeding adults.
Figure 2. Breeding distribution of the Least Bittern in Canada as of 2010 (dots indicate locations isolated from the known breeding range, but where birds have been found during the breeding season; Canadian Wildlife Service, unpublished data).
Despite recent advances in methods to detect the species (Meyer et al., 2006; Rehm and Baldassarre, 2007b; Tozer et al., 2007; Conway, 2009; Johnson et al. 2009, Jobin et al. 2010, 2011) which have led to increases in reported numbers of breeding individuals (Jobin, 2006, Latendresse and Jobin, 2007, Jobin et al. 2007, Meyer and Friis, 2008), there is a general consensus that the species has declined (Sandilands and Campbell, 1988; Austen et al., 1994; James, 1999; Environment Canada, 2007; Poole et al., 2009). In Canada, the species has shown declines in the heart of its Canadian range. For example, an average annual decline of 10.6% (95% CI = −6.9% to −14.3%) was noted in the Great Lakes Basin from 1995–2007 (Archer and Jones, 2009). An analysis of the data for Ontario yielded a similar trend (−10%/year, 95% CI = −5% to −16%, 1995–2006) and this takes into account that, overall, there was no significant change in the probability of observations between atlas projects (Cadman et al., 2007). Conversely, in the Lake Simcoe–Rideau zone, there was no significant change in the probability of observations (Cadman et al., 2007).
Current understanding of the ecological needs of Least Bitterns may be biased because selection of study sites and associated findings may be influenced by how easily the sites can be accessed and surveyed. Furthermore, the species' apparent habitat needs might be distorted by limitations in what habitat is available now compared to historically.
Least Bittern main breeding habitats consist of freshwater and brackish marshes with dense, tall, persistent emerging plants (mainly cattail Typha spp), interspersed with open water and occasionally clumps of shrubby vegetation (Parsons, 2002; Picard and Shaffer, 2003; Hay, 2006; Budd, 2007; Jobin et al., 2007; Yocum, 2007; Griffin et al., 2009). In Canada, these habitats are occupied from early May to early September (Fragnier, 1995). It appears that Least Bitterns may be relatively opportunistic in their habitat and nest site selection, provided that the available emerging vegetation can support and conceal their raised platform nest and that adequate foraging habitat is nearby (Nelson, 2003b; Arnold 2005). Least Bitterns are visual predators that forage for prey (e.g. small fish, tadpoles, insects) in clear shallow water near marsh edges, often from platforms that they construct out of bent vegetation (Poole et al., 2009). Moreover, marsh edges that border directly on deeper water are important for foraging, which probably explains why marshes interlaced with muskrat or other channels are preferred (Poole et al., 2009).
Naturally fluctuating water levels are an important habitat feature, at least during the breeding season, as high water levels would flood nests whereas low levels would reduce food availability and facilitate predators' access to nests (Arnold, 2005). Density of Least Bitterns may be affected by water depth, food abundance, vegetation type and cover availability more than marsh area or marsh area within the surrounding landscape (Arnold, 2005; Tozer et al. 2010).
Birds defending territories have been found in marshesas small as 0.4 ha (Gibbs and Melvin, 1990), but they usually nest in larger marshes (> 5 ha), especially those with a deeper open water zone (10–50 cm deep) and a roughly 50:50 ratio of vegetation to open water ("hemi–marsh" conditions; Rehm and Baldassarre, 2007a; Poole et al., 2009). The species can be semicolonial, particularly in highly productive habitats (Kushlan, 1973; Bogner, 2001; Meyer and Friis, 2008), where they can reach a density of up to five calling birds or nests per ha (Arnold, 2005; Poole et al., 2009). Although typically territorial, no definitive information exists on territory size and home range for Least Bitterns. Field data on Least Bittern movements, however, suggest that the average maximum distance travelled between two points by individual breeding birds is 393 m ± 36 SE (Bogner and Baldassarre, 2002a). A recent study by Griffin et al. (2009) even found a mean maximum distance of more than 2000 m in Missouri.
There is little information on habitat use during foraging, moulting, post–breeding dispersal, migration and on wintering areas although it is presumed that they possess similar properties to those of breeding habitats.
|Threat||Level of Concern1||Extent||Occurrence||Frequency||Severity2||Causal Certainty3|
|Habitat Loss or Degradation|
|Impaired water quality||Medium–High||Widespread||Current||Continuous/|
|Regulated water levels||Medium||Local||Current/|
|Exotic, Invasive or Introduced Species or Genome|
|Collisions with cars and anthropogenic structures||Low||Local||Current||Unknown||Unknown||Unknown|
|Disturbance or Harm|
|Climate and Natural Disasters|
|Natural Processes or Activities|
1 Level of Concern: signifies that managing the threat is of (high, medium or low) concern for the recovery of the species, consistent with the population and distribution objectives. This criterion considers the assessment of all the information in the table.
2 Severity: reflects the population–level effect (High: very large population–level effect, Moderate, Low, Unknown).
3 Causal certainty: reflects the degree of evidence that is known for the threat (High: available evidence strongly links the threat to stresses on population viability; Medium: there is a correlation between the threat and population viability e.g. expert opinion; Low: the threat is assumed or plausible).
4 Each threat is evaluated at the local level (each site) and at the rangewide level. When two items are present in a box, this means that the threat level is not the same for both scales (Local scale / Rangewide scale).
Threats are listed according to their level of concern. However, apart from wetland destruction and impaired water quality, the level of concern is speculative because the prevalence and impact of threats are poorly documented in Canada. Some threats may occur on wintering grounds and along migration routes with potentially important consequences on Least Bitterns that migrate to Canada for breeding. Some limiting factors such as the absence of muskrats (who open corridors in the marsh vegetation) and the reduction of natural disturbances (e.g. fires that prevent shrubs from invading the habitat) also have important effects.
Availability of suitable wetlands is the primary limiting factor for Least Bitterns because of their requirement for specific habitat characteristics which are limited across the range and as such may limit population size. Historic, anthropogenic loss of wetland habitat is thought to have severely reduced Least Bittern numbers across North America. The rate of large–scale wetland loss in southern Canada appears to have slowed in recent years, but wetlands continue to be drained for housing development and/or conversion to agricultural uses (Ducks Unlimited Canada 2010). In Québec, 80% of wetlands along the St. Lawrence River have been lost since European settlement (Painchaud and Villeneuve, 2003). Draining and filling of wetlands in southern Canada has slowed in recent years although habitat continues to be degraded through incremental encroachment and fragmentation (James, 1999). Development up to the edges of marshes, and fragmentation of marshes, for example by boat ramps, facilitates access to deeper portions of marshes by some mammalian predators, particularly raccoons (Jobin and Picman, 1997). Loss and degradation of wetlands is also an important factor in the United States (Dahl, 2006), affecting the migration and wintering habitats of the Canadian breeding population.
Impaired water quality
Run–off, siltation, acid rain and eutrophication can reduce prey abundance (Weller, 1999) and increase the likelihood of disease and toxicity. Any reduction in water clarity will likely reduce the foraging success of the Least Bittern, a visual feeder.
Single source pollution events such as toxic spills are particularly likely in marshes that border the busy shipping lanes of the St. Lawrence River and Great Lakes (Chapdelaine and Rail, 2004). The effects of such events on Least Bitterns have not been investigated but could be devastating since the species is known to bioaccumulate toxins in eggs and feathers (Causey and Graves, 1969).
Regulated water levels
Since water–level management along the St. Lawrence River and Lake Ontario was established in the 1950’s, the average maximum flow has decreased in summer and the average minimum flow has increased in winter (Morin and Leclerc, 1998). However, deviations from the regulation plan occur regularly and can impact Least Bittern during crucial periods (DesGranges et al., 2006). This situation may also be taking place in other important waterways such as the Ottawa River and even inland. Although Least Bitterns are able to adjust nest height somewhat in response to higher water levels (Nelson, 2003a), they seem to occupy sites where water levels are stable during the breeding season. Any dramatic change in water levels during the breeding season is liable to affect the species negatively, either directly by flooding nests (Guillemette and Messier, 2009), increasing the likelihood of depredation and impeding foraging or indirectly by degrading the habitat. The species reaction to decreasing water levels over the long term is more pronounced when sharp declines with few flooded areas are available than when the trend is declining but with a more cyclical presence of high water levels (Timmermans et al., 2008).
Prolonged periods of high water levels can reduce the extent of cattail marshes, both directly and by making conditions more favourable for other species such as Wild Rice (Zizania palustris) that are less suitable for nesting Least Bitterns (Sandilands and Campbell, 1988). Conversely, prolonged periods of relatively stable water levels may increase the density of cattail stands and eliminate open pools required by Least Bitterns. However, periodic draining of wetland cells for habitat management and restoration purposes which generally occur outside of bird breeding season is a measure which largely benefits waterbirds in the long–term (Parsons et al., 2002; Arnold, 2005). Jobin et al. (2009) showed that the abundance of a Least Bittern population was reduced rapidly following a strong decrease of water depth in impounded wetlands followed by a rapid increase in abundance when water depth later returned to previous levels.
Several species of invasive plants and animals are increasing in range and abundance in North American marshes, largely due to human actions. Purple Loosestrife (Lythrum salicaria), Reed Canary Grass (Phalaris arundinacea), European Common Reed (Phragmites autralis spp. australis) and Flowering Rush (Butomus umbellatus) have spread across North America, crowding out native emergent vegetation such as cattails (Lavoie et al., 2003; Hudon, 2004; Jobin, 2006; Jobin et al., 2007; Latendresse and Jobin, 2007). While Least Bitterns can breed in a variety of emergents, including stands of invasive species such as European Common Reed and Flowering Rush, they preferentially breed in cattails (Poole et al., 2009). Invasive species may provide suboptimal habitat, although actual use of these vegetation communities is unknown. Invasive plants, including those that do not compete directly with cattails (e.g., European Frog–bit [Hydrocharis morsus–ranae] and Water Chestnut [Trapa natans]), can also alter habitat structure or have a variety of more indirect effects on marsh habitat, particularly in accelerating marsh succession to drier conditions that are not optimal to breeding Least Bitterns (Blossey et al., 2001).
Populations of invasive fish and invertebrates, for example Carp (Cyprinus carpio), Round Goby (Neogobius melanostomus), Quagga and Zebra mussels (Dreissena bugensis and D. polymorpha), are also increasing in wetlands occupied by Least Bitterns, especially in southern Ontario and Québec. In addition to their numerous deleterious effects on ecosystem function, some of them may impact Least Bitterns more directly. For example, Carp can impact populations of smaller fish that Least Bitterns eat by eating their eggs at the same time as vegetation, and stir up sediment as they forage, reducing water clarity for visual feeders such as Least Bitterns (Wires et al., 2010).
Collisions with cars and anthropogenic structures
Least Bitterns fly at low levels and also migrate at night, characteristics which make them susceptible to collisions with vehicles, buildings, guy wires, power lines, barbed wire fences, and towers. These collisions may be frequent enough at some sites to threaten local populations (Poole et al., 2009). In one example, 12 Least Bitterns were killed in collisions with vehicles and four died after being impaled on a fence during one weekend on a road that passes through a refuge in Louisiana (Guillory, 1973). Least Bitterns have been found dead along the Long Point (Ontario) causeway on a few occasions (Ashley and Robinson, 1996; J. McCracken, unpubl. data). These incidents suggest that roadways or structures built adjacent to patches of suitable marsh habitat can cause mortality for birds moving between wetlands or during migration.
Although Least Bitterns can tolerate a certain level of human activity near their breeding marshes, including the passage of boats near their foraging areas (Poole et al., 2009), they seem to prefer nesting outside urban areas (Smith–Cartwright and Chow–Fraser, unpublished results). Infrequent and unpredictable disturbance, however, may be as disruptive to Least Bitterns as it is for other species that are intolerant of human activity (Nisbet, 2000). Frequent use of call–broadcasts by recreational birders in wetlands where birding pressure is intense may also be disruptive to breeding Least Bitterns. As well, direct impacts such as waves from motorized watercraft could erode marsh edges and possibly flood or upset nests.
Climate change has the potential of having unpredictable, widespread and severe effects on Least Bitterns and their habitat. Climate change could increase the frequency of events such as floods and storms that can destroy nests and habitat, and may also change the overall hydrological and temperature regimes that account for the Least Bittern's distribution in Canada. In the Great Lakes, for example, water temperature will likely rise, reducing seasonal mixing, increasing algal blooms, and lowering water levels, all with important effects on the ecosystem (AMEC Earth and Environmental, 2006). Reduction of water levels, in particular, will likely reduce the area of emergent marsh, reducing both prey and habitat for Least Bitterns (Mortsch et al., 2007; Wires et al., 2010). Modeling scenarios of changing hydrology of the St. Lawrence–Great Lakes hydrosystem forecast that water level fluctuations downstream may induce widespread nest destruction of breeding marsh birds, including the Least Bittern, along the St. Lawrence River shorelines (DesGranges et al., 2006). On the other hand, a northward expansion by the species could favour the use of numerous wetlands in the boreal forest although the quality of these habitats for breeding purposes would need to be assessed.
Finally, increased penetration of water by ultraviolet radiation as a result of depletion of the ozone layer has negative impacts on the productivity of aquatic ecosystems (Persaud and Yan, 2005, and references cited therein), and hence could reduce food supplies of Least Bitterns.
Although most nest losses have been attributed to abandonment, depredation, cannibalism and flooding (Nelson, 2003b; Griffin et al., 2009; Poole et al., 2009), various diseases and parasitism from nematodes, trematodes, lice and mites have been reported but have been poorly studied in Least Bittern. Presumably, the species is susceptible to diseases known to affect other wading birds, namely chlamydial infection, type C botulism, avian cholera, aspergillosis, sarcocystis (Friend, 1987; cited in Gibbs and Melvin, 1992), avian salmonellosis (Friend and Franson, 1999), Eustrongilides, a nematode particularly prevalent in the presence of nutrient and silt–laden run–off (P. Frederick, personal communication, cited in Gibbs and Melvin, 1992), and avian salmonella, outbreaks of which may be associated with sewage effluents (Wires et al., 2010). Furthermore, Least Bittern is one of 326 bird species in which West Nile Virus has been found (Center for Disease Control, 2009).
The population and distribution objectives for the Least Bittern are to maintain and, where possible, increase the current Canadian population size and area of occupancy. An increase in population and area of occupancy is considered possible in many parts of the range where adequate, yet currently unoccupied, breeding, foraging, post–dispersal, moulting and migration stopover habitat is available or could be restored. These objectives can only be achieved over the long term (>10 years). The species' historical abundance and distribution are not well known, and specific habitat needs for different life stages and locations across its Canadian range are not understood well enough at present to set quantitative objectives. This may become possible in subsequent iterations of this recovery strategy as knowledge gaps are filled.
The following activities have been undertaken in Canada since 2000:
- Literature reviews of all available information on Least Bitterns (McConnell, 2004 ; Gray Owl Environmental Inc., 2009);
- National Least Bittern survey protocol for the breeding season (Jobin et al., 2010, 2011);
- National protocol for capturing, banding, radio–tagging and tissue sampling Least Bitterns in Canada (MacKenzie and McCracken, 2011);
- Surveys of potential and historical sites have been conducted in many portions of southern Manitoba (2003–2008; R. Bazin comm. pers.; Hay, 2006), Ontario (2001–2010; Bowles, 2002; Desy, 2007; Meyer and Friis, 2008) and Québec (2004–2010; Jobin, 2006; Jobin et al., 2007; Latendresse and Jobin, 2007; Guillemette and Messier, 2009; Jobin and Giguère, 2009);
- Second Breeding Bird Atlas published in Ontario (2001–2005; Cadman et al., 2007), fieldwork completed for the second Atlas in the Maritimes (2005–2010) and fieldwork started for the second Atlas in Quebec and Manitoba (2010);
- Directed surveys in National Wildlife Areas in Ontario and Québec;
- Masters and PhD theses completed on Least Bittern breeding habitat in Ontario (N. Bartok–University of Western Ontario; P. Quesnelle–Carleton University; D. Tozer – Trent University) and Manitoba (S. Hay–University of Manitoba);
- On–going monitoring programs: Great Lakes Coastal Wetland Monitoring Program (Canadian Wildlife Service–Ontario region; Meyer et al., 2006); Marsh Monitoring Program in Ontario since 1994 and in Québec since 2004; Monitoring of Least Bittern presence in several wetlands in southern Québec as part of the avian species at risk yearly breeding sites monitoring (SOS–POP); Prairies and Parkland pilot Marsh Monitoring Program since 2008.
- Upcoming creation of the Samuel–De Champlain projected biodiversity reserve (Natural heritage conservation Act of Québec; R.S.Q. c. C–61.01) which will protect 487 ha of wetlands on the shores of the Richelieu River near the Quebec/USA border. This will include two of the sites containing Least Bittern critical habitat (Baie McGillivray and Rivière Richelieu–Frontière).
- Broad efforts to protect, manage, and restore wetlands in Ontario are ongoing, for example, through the Eastern Habitat Joint Venture of the North American Waterfowl Management Plan, Great Lakes Sustainability Fund, and other programs.
- The Walpole Island First Nation is developing an ecosystem protection plan based on the community’s Traditional Ecological Knowledge.
Critical habitat is partially identified for Least Bitterns in Canada. As there is limited information concerning most foraging, moulting, post–breeding dispersal and migration stopover habitats, critical habitat is only identified for the breeding habitat.
The identification of critical habitat for the Least Bittern is based on two aspects: habitat suitability and habitat occupancy.
Habitat suitability relates to the areas where individuals carry out various aspects of their breeding cycle (i.e., courtship, territory defense, feeding, nesting, and post–fledgling). Suitable breeding habitat for Least Bitterns consists of those areas within the high–water mark of permanent wetlands (marshes and shrubby swamps) containing tall and robust emergent herbaceous and/or woody vegetation interspersed with areas of open water.
Based on field data on Least Bittern movements which suggest that the average maximum distance travelled between two points by individual breeding birds is 393 m ± 36 SE (Bogner and Baldassarre, 2002b), suitable habitat extends up to 500 m of documented breeding activity.
Habitat occupancy relates to areas of suitable habitat that have documented breeding activity (probable or confirmed records; see Appendix A for definitions) and between–season fidelity (suitable habitat where Least Bitterns have returned to breed in multiple years). Since Least Bitterns may occupy marshes in a specific area for only one year and never be observed there again (i.e. some marshes are used sporadically but not necessarily for breeding), documented breeding activity in suitable habitat for at least two years is a stronger criteria to identify critical breeding habitat.
The use of the probable or confirmed evidence of breeding is consistent with criteria developed by species at risk experts to document Least Bittern observations within the Quebec conservation data centre database as it can be very difficult to confirm breeding in this species (e.g. secretive behaviour, pairs are very rarely seen and nests/fledglings are rarely found; Tozer et al., 2007). For example, out of 185 sites where Least Bitterns were detected in Canada between April and August (as of 2007), breeding had only been confirmed in 26 (14%).
Given that wetland habitats are dynamic throughout the Canadian range, recent information may be more reliable for evaluating suitable wetland habitat and Least Bittern use. In light of this fact, the threshold year of 2001 has been identified as an appropriate time frame for including Least Bittern breeding records as this is the year when the second Ontario Breeding Bird Atlas data started to be gathered (Ontario has the core breeding population in Canada). Records older than 2001 would need to be validated to determine the continued presence of suitable habitat and current use by Least Bitterns.
Critical habitat is identified in this recovery strategy as the area of suitable habitat with 500 m of documented breeding activity consisting of either :
- One or more records of confirmed breeding since 2001;
- A minimum of two records of probable breeding in any single year since 2001 OR at least one record of probable breeding evidence in each of 2 separate years within a floating 5–year window since 2001.
All the habitat (suitable or not) within 500 m of documented breeding activity is referred to as a site. A site can be a whole wetland or part of a wetland in the event that only portions of that wetland have records of breeding activity. Therefore, several critical habitat sites may occur within a large wetland but adjacent sites merge into larger sites in cases of overlap.
Using these criteria, Least Bittern critical habitat has been identified at 98 sites, including 10 in Manitoba, 44 in Ontario, 42 in Québec and 2 in New Brunswick (Appendix B). It is important to note that the data in Appendix B are presenting sites containing critical habitat, and not the critical habitat itself. The extent and boundaries of the critical habitat within each site are defined by the extent of suitable habitat as defined in Section 7.1.1.
Least Bitterns may occasionally nest in non–traditional sites (e.g. roadside ditches, sewage lagoons) that are anthropogenic in nature and do not provide sustained quality breeding habitat given that they may be the object of frequent interventions that could negatively affect breeding Least Bitterns. Correspondingly, these sites are not identified as critical habitat under SARA (even if breeding is confirmed), although the general prohibitions under SARA and the Migratory Birds Convention Act, 1994 (S.C., 1994, c. 22) protecting the birds and their residences (nests) from damage or destruction will remain in effect.
|Description of Activity||Rationale||Timeline|
Conduct surveys and habitat assessments at priority sites in which:
|Additional critical habitat identified, particularly in more remote areas||2011–2016|
|Identify sites containing foraging, post–breeding dispersal, moulting and migration stopover critical habitat in Canada||Needed to protect and ensure long–term survival in Canada||2011–2016|
a The 1990 year has been selected based on the fact that Conservation Data Centers consider records older than 20 years to be historical.
Destruction is determined on a case by case basis. Destruction would result if part of the critical habitat was degraded, either permanently or temporarily, such that it would not serve its function when needed by the species. Destruction may result from a single activity or multiple activities at one point in time or from the cumulative effects of one or more activities over time (Governement of Canada, 2009). Examples of activities that are likely to result in destruction of critical habitat include, but are not limited to:
1) Activities causing permanent loss of wetlands identified as critical habitat such as infilling (e.g. infrastructure development and construction), draining, dredging and channelization (e.g. for agriculture), and resource extraction preventing the use of sites during the breeding, foraging, post–breeding–dispersal, moulting or migrating stages.
2) Activities that degrade critical habitat or alter their function to the point where it can no longer serve for the Least Bittern:
- Infilling, dredging, channelization that leads to the development of unsuitable vegetation within the marsh;
- Agricultural activities that generate soil run–off and increased water turbidity or nutrient influx which can lead to vegetation overgrowth and render the habitat inhospitable (e.g. reduced foraging success);
- Deliberate introduction of invasive vegetation, fish and invertebrate species that alter feeding activities and are unsuitable for nest building;
- Use of vehicles and motor boats within wetlands, causing water level and habitat changes;
- Prescribed burns or other means of natural vegetation removal within wetland habitats during the breeding season due to their effects on nesting activities;
- Deposition of deleterious substances, either directly (in water) or indirectly (upstream, soil), into wetlands that would affect water quality (e.g., chemicals, silt);
- Dumping of snow with salts or other abrasives in wetlands during snow removal operations as this may alter water quality and feeding success.
- Construction of infrastructures (e.g. roads, houses, boat ramps) which increase the access to critical habitat and can lead to disturbance of reproductive activities or increase other threats (e.g. collisions).
- Trampling by livestock that removes or tramples substantial amounts of standing emergent aquatic vegetation and erodes the banks.
Activities required to manage, inspect and maintain existing facilities and infrastructure which are not critical habitat but whose footprints may be within or adjacent to the identified critical habitat are not examples of activities likely to result in the destruction of critical habitat provided that they are carried out in a manner aimed at protecting the Least Bittern critical habitat. Therefore, management of wetlands for wildlife conservation purposes does not typically result in destruction of critical habitat.
The performance indicators presented below provide a way to define and measure progress toward achieving the population and distribution objectives. Every five years, the success of this recovery strategy will be measured against indicators outlined below.
- the population size of Least Bittern is maintained and, where possible, increased;
- the area of occupancy of sites with probable or confirmed records of Least Bittern breeding evidence is maintained and, where possible, increased.
One or more action plans will be posted on the Species at Risk Public Registry for the Least Bittern before 2016.
AMEC Earth and Environmental. 2006. Coastal zone and climate change in the Great Lakes. Unpubl. Rep. to Natural Resources Canada (Climate Change Action Fund), Ottawa, Ontario. 142 pp.
Arnold, K.E. 2005. The Breeding Ecology of Least Bitterns (Ixobrychus exilis) at Agassiz and Mingo National Wildlife Refuges. MSc thesis, South Dakota State University, Brookings, South Dakota.
Archer, R.W. and K.E. Jones. 2009. The Marsh Monitoring Program Annual Report, 1995–2007. Annual indicies and trends in bird abundance and amphibian occurrence in the Great Lakes basin. Report for Environment Canada by Bird Studies Canada, Port Rowan, ON.
Ashley, E.P. and J.T. Robinson. 1996. Road mortality of amphibians, reptiles and other wildlife on the Long Point causeway, Lake Erie, Ontario. Canadian Field–Naturalist 110: 403–412.
Austen, M.J.W., M.D. Cadman, and R.D. James. 1994. Ontario Birds at Risk: Status and Conservation Needs. Federation of Ontario Naturalists and Long Point Bird Observatory, Toronto and Port Rowan, Ontario.
BirdLife International 2009. Ixobrychus exilis. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2009.2. (Accessed on 8 December 2009).
Bird Studies Canada. 2009. BirdMap Canada. A source of information on bird distribution and movements. http://birdmap.bsc-eoc.org/maps/birdmap/viewer.htm [accessed December 2009].
Bird Studies Canada. 2010. Maritimes Breeding Bird Atlas [accessed July 2010].
Blossey, B., L.C. Skinner, and J. Taylor. 2001. Impact and management of purple loosestrife (Lythrum salicaria) in North America. Biodiversity and Conservation 10: 1787–1807.
Bogner, H.E. 2001. Breeding biology of Least Bittern (Ixobrychus exilis) in western New York. MSc thesis, State University of New York, Syracuse.
Bogner, H.E., and G.A. Baldassarre. 2002a. The effectiveness of call–response surveys for detecting least bitterns. Journal of Wildlife Management 66: 976–984.
Bogner, H. E., and G. A. Baldassarre. 2002b. Home range, movement and nesting of Least Bitterns in western New York. Wilson Bulletin. 114: 297–308.
Bowles, R. 2002. Least Bittern surveys in Simcoe County, Ontario. Unpublished manuscript, Canadian Wildlife Service.
Budd, M.J. 2007. Status, distribution, and habitat selection of secretive marsh birds in the delta of Arkansas. M.Sc. thesis, University of Arkansas, Fayetteville, Arkansas, USA.
Cadman, M.D., D.A. Sutherland, G.G. Beck, D. Lepage, and A.R. Couturier (eds.). 2007. Atlas of the Breeding Birds of Ontario, 2001–2005. Bird Studies Canada, Environment Canada, Ontario Field Ornithologists, Ontario Ministry of Natural Resources, and Ontario Nature, Toronto, xxii + 706 pp.
Causey, M.K., and J.B. Graves. 1969. Insecticide residues in Least Bittern eggs. Wilson Bulletin 81:340–341.
Center for Disease Control. 2009. Division of Vector–Borne Infectious Diseases. West Nile Virus. For more information, read the Important Notices at the bottom of this page, (accessed: 10 December 2009).
Champoux, L., J. Rodrigue, S. Trudeau, M.H. Boily, P.A. Spear, and A. Hontela. 2006. Contamination and biomarkers in the Great Blue Heron, an indicator of the state of the St. Lawrence River. Ecotoxicology 15: 83–96.
Chapdelaine, G., and J.–F. Rail. 2004. Québec’s Waterbird Conservation Plan. Migratory Bird Division, Canadian Wildlife Service, Québec Region, Environment Canada, Sainte–Foy, Québec. 99 pp.
Conway, C.J. 2009. Standardized North American Marsh Bird Monitoring Protocols. Wildlife Research Report #2008–1. U.S. Geological Survey, Arizona Cooperative Fish and Wildlife Research Unit, Tucson, AZ. 57 pp.
COSEWIC. 2009. COSEWIC assessment and update status report on the Least Bittern Ixobrychus exilis in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 36 pp.
Dahl, T.E. 2006. Status and trends of wetlands in the conterminous United States 1998 to 2004. U.S. Department of the Interior; Fish and Wildlife Service, Washington, D.C. 112 pp.
Delany, S., and D. Scott. 2006. Waterbird population estimates. Fourth Edition. Wetlands international, Wageningen, 239 pp.
DesGranges, J.–L., J. Ingram, B. Drolet, J. Morin, C. Savage, and D. Borcard. 2006. Modelling wetland bird response to water level changes in the Lake Ontario–St. Lawrence River hydrosystem. Environmental Monitoring and Assessment 113: 329–365.
Desy, G.E. 2007. Summary report for Least Bittern surveys conducted at Long Point and Big Creek National Wildlife Areas, Ontario. Submitted to Environment Canada, Canadian Wildlife Service, Ontario Region.
Ducks Unlimited Canada. 2010. Southern Ontario Wetland Conversion Analysis (PDF, 3.4 MB). Final Report. Ducks Unlimited Canada–Ontario Office, Barrie, Ontario.
Environment Canada. 1986. Wetlands in Canada: a valuable resource. Fact Sheet 86–4 ed. Ottawa, Ontario.
Environment Canada. 2007. Least Bittern Species Profile. Species at Risk Public registry website.
Erskine, A.J. 1992. Atlas of Breeding Birds of the Maritime Provinces. Nimbus and the Nova Scotia Museum, Halifax, Nova Scotia. 280 pp.
Fragnier, P. 1995. Least Bittern. In J. Gauthier and Y. Aubry (eds.) The Breeding Birds of Québec: Atlas of the Breeding Birds of Southern Québec. Association québecoise des groupes d'ornithologues, Province of Québec Society for the Protection of Birds, Canadian Wildlife Service, Environment Canada – Québec region, Montréal. 1295 pp.
Friend, M. 1987. Field guide to wildlife diseases. Vol. 1: General field procedures and diseases of migratory birds. Fish and Wildlife Service Resource Publication 167. 225 pp.
Friend, M., and J. C. Franson. Eds. 1999. Field Manual of Wildlife Diseases: U.S. Geological Survey, Biological Resource Division, National Wildlife Health Center, Madison, Wisconsin.
Gibbs, J.P., and S.M. Melvin. 1990. An assessment of wading birds and other wetland avifauna and their habitat in Maine. Final Report, Maine Deptartment of Inland Fisheries and Wildlife, Bangor, ME.
Gibbs, J.P., and S.M. Melvin. 1992. Least bittern, Ixobrychus exilis. Pages 71–88 in K.J. Schneider and D.M. Pence, editors. Migratory nongame birds of management concern in the Northeast. U.S. Fish and Wildlife Service, Newton Corner, Massachusetts.
Giguère, S., J. Ingram, B. Drolet, J.–L. DesGranges, and P. Laporte. 2005. Least Bittern (Ixobrychus exilis) reproductive index in emergent marshes. International Lake Ontario–St. Lawrence River Study Technical Work Group.
Government of Canada. 1991. The Federal Policy on Wetland Conservation. Environment Canada, Ottawa, Ontario. CW66–116/1991E
Government of Canada. 2009. Species at Risk Act Policies, Overarching Framework [Draft]. Species at Risk Act Policy and Guideline Series. Environment Canada. Ottawa. 38 pp.
Gray Owl Environmental Inc. 2009. Least Bittern literature review and a preliminary survey protocol. Prepared for the Canadian Wildlife Service – Ontario Region. 95 pp.
Griffin, A. D., F. E. Durbian, D. A. Easterla and R. L. Bell. 2009. Spatial ecology of breeding Least Bitterns in northwest Missouri. Wilson Journal of Ornithology 121: 521–527.
Guillemette, J., and P. Messier. 2009. Inventaire du Petit Blongios dans les marais riverains au lac Saint–Pierre, été 2008. Rapport inédit présenté à Environnement Canada, Service canadien de la faune, région du Québec. 26 pp.
Guillory, H.D. 1973. Motor vehicles and barbed wire fences as major mortality factors for the Least Bittern in southwestern Louisiana. Inland Bird Banding News 45: 176–177.
Hay, S. 2006. Distribution and Habitat of the Least Bittern and Other Marsh Bird Species in Southern Manitoba. Masters of Natural Resource Management thesis, University of Manitoba, Winnipeg, Manitoba.
Hudon, C. 2004. Shift in wetland plant composition and biomass following low–level episodes in the St.Lawrence River: Looking into the future. Canadian Journal of Fisheries and Aquatic Sciences 61: 603–17.
James, R.D. 1999. Update status report on the Least Bittern Ixobrychus exilis in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. 12 pp.
Jobin, B. 2006. Inventaire du Petit Blongios dans le parc national de Plaisance, été 2005. Série de rapports techniques No. 457, Service canadien de la faune, région du Québec, Environnement Canada, Sainte–Foy, 40 pp. et annexes.
Jobin, B., and J. Picman. 1997. Factors affecting predation on artificial nests in marshes. Journal of Wildlife Management 61: 792–800.
Jobin, B., and S. Giguère. 2009. Inventaire du Petit Blongios et de la Tortue des bois à la garnison Farnham du ministère de la Défense nationale, été 2008. Environnement Canada, Service canadien de la faune, région du Québec. Rapport non publié. 34 p. et annexes.
Jobin, B., C. Latendresse et L. Robillard. 2007. Habitats et inventaires du Petit Blongios sur les terres du ministère de la Défense nationale à Nicolet, Québec, étés 2004, 2005 et 2006. Série de rapports techniques no 482, Service canadien de la faune, région du Québec, Environnement Canada, Sainte–Foy, Québec, 85 pp. et annexes.
Jobin, B., L. Robillard and C. Latendresse. 2009. Response of a Least Bittern (Ixobrychus exilis) population to interannual water level fluctuations. Waterbirds 32: 73–80.
Jobin, B., R. Bazin, L. Maynard, A. McConnell and J. Stewart. 2010. National Least Bittern Survey Protocol. Environment Canada, Canadian Wildlife Service. Québec Region. Unpublished report. 26 pp.
Jobin, B., R. Bazin, L. Maynard, A. McConnell and J. Stewart. 2011. Least Bittern (Ixobrychus exilis) survey protocol. Waterbirds 34: 225–233.
Johnson, D.J., J.P. Gibbs, M. Herzog, S. Lor, N.D. Niemuth, C.A. Ribic, M. Seamans, T.L. Schaffer, G. Shriver, S. Stehman, and W.L. Thompson. 2009. A sampling design framework for monitoring secretive marshbirds. Waterbirds 32: 203–215.
Kent, T. 1951. The Least Bitterns of Swan Lake. Iowa Bird Life 21: 59–61.
Kushlan, J. A. 1973. Least Bittern nesting colonially. Auk 90: 685–686.
Kushlan, J.A., and J.A. Hancock. 2005. Herons. Oxford University Press, Oxford.
Latendresse, C., and B. Jobin. 2007. Inventaire du Petit Blongios à la baie McLaurin et au marais aux Massettes, région de l’Outaouais, été 2006. Environnement Canada, Service canadien de la faune, région du Québec, Sainte–Foy. Rapport inédit. 40 p. et annexes.
Lavoie, C., M. Jean, F. Delisle, and G. Létourneau. 2003. Exotic plant species of the St.Lawrence River wetlands: a spatial and historical analysis. Journal of Biogeography 30: 537–49.
Mackenzie, S.A., and J.D. McCracken. 2011. National protocol for capturing, banding, radio–tagging and tissue sampling Least Bitterns in Canada. Prepared for Environment Canada, Canadian Wildlife Service and the National Least Bittern Recovery Team. Bird Studies Canada, 30 pp.
McConnell, A. 2004. Draft Least Bittern Background Report, Version 1.0. Prepared for the Canadian Wildlife Service, Environment Canada, Ontario Region.
McKercher, R.B., and B. Wolf. 1986. Understanding Western Canada's Dominion Land Survey System. Saskatoon: Division of Extension and Community Relations, University of Saskatchewan.
Meyer, S.W. and C.A. Friis. 2008. Occurrence and habitat of breeding Least Bitterns at St. Clair National Wildlife Area. Ontario Birds 26: 146–164.
Meyer, S.W., J.W. Ingram, and G.P. Grabas. 2006. The Marsh Monitoring Program: Evaluating marsh bird survey protocol modifications to assess Lake Ontario coastal wetlands at a site–level. Technical Report Series 465. Canadian Wildlife Service, Ontario region, Ontario.
Morin, J. and M. Leclerc. 1998. From prestine to present state: hydrology evolution of Lake Saint–Francois, St. Lawrence River. Canadian Journal of Civil Engineering 25: 864–879.
Mortsch, L., J. Ingram, A. Hebb, and S. Doka (eds). 2007. Great Lakes Coastal Wetland Communities: Vulnerability to Climate Change and Response to Adaptation Strategies. Final Report.
Nankinov, D.M. 1999. On the question of distribution and migrations of the Little Bittern. Berkut 8:15–20.
NatureServe. 2010. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Available (accessed january 26th 2011).
Nelson, F.A. 2003a. Habitat Selection and Breeding Ecology of Least Bitterns (Ixobrychus exilis) in Northwest Missouri on Squaw Creek National Wildlife Refuge, M.S. thesis, University of Missouri, Columbia. 88 pp.
Nelson, F.A. 2003b. Least Bittern, Squaw Creek National Wildlife Refuge Summary. Unpublished report.
Nisbet, I.C.T. 2000. Disturbance, habituation, and management of waterbird colonies. Waterbirds 23: 312–332.
Painchaud, J., et Villeneuve, S. 2003. Portrait global de l’état du Saint–Laurent–Suivi de l’état du Saint–Laurent. Plan d’action Saint–Laurent Vision 2000. Bibliothèque Nationale du Canada. 18 pp.
Parsons, K.C. 2002. Integrated management of waterbird habitats at impounded wetlands in Delaware Bay, U.S.A. Waterbirds 25: 25–41.
Parsons, K.C., S.C. Brown, R.M. Erwin, and H.A. Czech. 2002. Managing wetlands for waterbirds: Integrated approaches. Waterbirds 25: 1–4.
Peer, B.D. 2006. American Coot parasitism on Least Bitterns. Wilson Journal of Ornithology 118: 415–418.
Persaud, A.D., and N.D. Yan. 2005. Developmental differences and a test for reciprocity in the tolerance of Chaoborus punctipennis larvae to ultraviolet radiation. Canadian Journal of Fisheries and Aquatic Science 62: 483–491.
Picard, M., and F. Shaffer. 2003. Caractérisation de l’habitat de nidification du Petit Blongios (Ixobrychus exilis) au Québec : marais de l’île aux Fermiers, Varennes, 2000. Série de rapports techniques No 402, Service canadien de la faune, région du Québec, Environnement Canada, Sainte–Foy, 22 p.
Poole, A.F., P. Lowther, J. P. Gibbs, F. A. Reid and S. M. Melvin. 2009. Least Bittern (Ixobrychus exilis), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: (accessed march 30th 2011)
Post, W., and C.A. Seals. 2000. Breeding biology of the common moorhen in an impounded cattail marsh. Journal of Field Ornithology 71(3):437– 442
Province of New Brunswick. 2002. New Brunswick Atlas, Second Edition Revised. Nimbus Publishing and Service New Brunswick.
Rehm, E.M. and G.A. Baldassarre. 2007a. The influence of interspersion on marsh bird abundance in New York. Wilson Journal of Ornithology 119: 648–654.
Rehm, E.M. and G.A. Baldassarre. 2007b. Temporal variation in detection of marsh birds during broadcast of conspecific calls. Journal of Field Ornithology 78: 56–63.
Sandilands, A.P., and C.A. Campbell. 1988. Status report on the Least Bittern Ixobrychus exilis. Committee on the Status of Endangered Wildlife in Canada. Ottawa, Ontario. 34 pp.
Sibley, D.A. 2000. The Sibley Guide to Birds. Knopf, New York.
Smith–Cartwright, L., et L. Chow–Fraser. Landscape–scale influences on Least Bittern (Ixobrychus exilis) habitat use in southern Ontario coastal marshes. Unpublished results.
Timmermans, S.T.A., S.S. Badzinski, and J.W. Ingram. 2008. Associations between breeding marsh bird abundances and Great Lakes hydrology. Journal of Great Lakes Research 34:351–364.
Tori, G.M., S. McLoed, K. McKnight, T. Moorman, and F.A. Reid. 2002. Wetland conservation and Ducks Unlimited: Real world approaches to multispecies management. Waterbirds 25: 115–121.
Tozer, D.C., E. Nol, and K.F. Abraham. 2010. Effects of local and landscape–scale habitat variables on abundance and reproductive success of wetland birds. Wetlands Ecology and Management 18: 679–693.
USFWS. 2002. Birds of conservation concern 2002. U. S. Fish and Wildlife Service, Division of Migratory bird Management. Arlington, Virginia.
Weller, M.W. 1999. Wetland Birds: Habitat Resources and Conservation Implications. Cambridge University Press, Cambridge.
Wires, L.R., S. J. Lewis, G. J. Soulliere, S. W. Matteson, D. V. Weseloh, R. P. Russell, and F. J. Cuthbert. 2010. Upper Mississippi Valley / Great Lakes Waterbird Conservation Plan. A plan associated with the Waterbird Conservation for the Americas Initiative. Final Report submitted to the U. S. Fish and Wildlife Service, Fort Snelling, MN.
Yocum, B.J. 2007. Breeding biology of and nest site selection by Least Bitterns (Ixobrychus exilis) near Saginaw Bay, Michigan. M.Sc. thesis, Central Michigan University, Mount Pleasant, Michigan, USA.
|Evidence of probable breeding|
|P||Pair observed in their breeding season in suitable nesting habitat|
|T||Permanent territory presumed through registration of territorial behaviour (song, etc.), or the occurrence of an adult bird, on at least two days, a week or more apart, at the same place, in suitable nesting habitat during the breeding season|
|D||Courtship or display between a male and a female or two males including courtship, feeding or copulation|
|V||Visiting probable nest site|
|A||Agitated behaviour or anxiety calls of an adult indicating nest–site or young in the vicinity|
|B||Brood patch on adult female or cloacal protuberance on adult male|
|NB||Nest building or carrying nest materials|
|DD||Distraction display or injury feigning|
|NU||Used nest or egg shells found (occupied or laid within the period of the survey). Use only for unique and unmistakable nests or shells|
|FY||Recently fledged young or downy young|
|AE||Adults leaving or entering nest sites in circumstances indicating occupied nest (including nests which content cannot be seen)|
|FS||Adult carrying fecal sac|
|CF||Adult carrying food for young during its breeding season|
|NE||Nest containing eggs|
|NY||Nest containing young seen or heard|
|* Atlas codes and descriptions can vary slightly from one province to another but convey similar meanings.|
|No.||Site name||NTS Map (1:50,000)1||Quarter section identification2||Latitude and longitude of site centroid||Area (ha)3||Description||Land tenure4|
|111||Freshwater wetland located east of PR302, north of Hwy 1 and south of Hwy 15 near the town of Ross, Manitoba||Non federal|
|241||Freshwater Lake located north of PR419, east of PR512 and north of Hwy 17 near the town of Chatfield, Manitoba||Non federal|
|3||Fish Lake||62I11 and 62I14||SW–30–20–02–E1|
|131||Freshwater wetland located east of Hwy 17 and west of Hwy 7 near the town of Meleb, Manitoba||Non federal|
|4||Little Birch Lake West||62O01||SW–11–25–05–W1|
|104||Freshwater wetland located south of PR325 and north of Sleeve Lake near the town of Ashern, Manitoba||Non federal|
|5||Little Birch Lake East||62O01||SE–12–25–05–W1|
|79||Freshwater wetland located south of PR325 and north of Sleeve Lake near the town of Ashern, Manitoba||Non federal|
|6||Rat River Swamp West||62H02 and 62H07||NW–20–03–06–E1|
|693||Freshwater wetland located east of Hwy 59, west of PR302 and north of the Vita Drain along the Rat River near the towns of Rosa and Zhoda, Manitoba||Non federal|
|7||Rat River Swamp Centre||62H02 and 62H07||NW–26–03–06–E1|
|125||Freshwater wetland located east of Hwy 59, west of PR302 and north of the Vita Drain along the Rat River near the towns of Rosa and Zhoda, Manitoba||Non federal|
|8||Rat River Swamp East||62H02 and 62H07||NW–34–03–07–E1|
|190||Freshwater wetland located east of Hwy 59, west of PR302 and north of the Vita Drain along the Rat River near the towns of Rosa and Zhoda, Manitoba||Non federal|
|79||Freshwater wetland located south of PR325 and south of Little Birch Lake near the town of Ashern, Manitoba||Non federal|
|10||Unnamed Lake (locally called Little Sleeve Lake)||62O01||NE–36–24–05–W1|
|103||Freshwater wetland located south of PR325 between Little Birch Lake and Sleeve Lake near the town of Ashern, Manitoba||Non federal|
1 National Topographic System
2 Quarter section descriptions are based on the Dominion Land Survey System, whereby most of western Canada is legally divided into townships based on longitudinal meridians and latitudinal base lines. Each township is given a township number and range number. Townships are approximately 9.7 km x 9.7 km (6 miles x 6 miles) and are further divided into thirty–six sections, each about 1.6 km x 1.6 km (1 mile x 1 mile). In turn, each section is divided into four quarter sections: southeast, southwest, northwest and northeast, which are 0.8 km x 0.8 km (0.5 mile x 0.5 mile). For example, the full legal description of quarter section NW–36–002–06–E is the Northwest Quarter of Section 36, Township 002, Range 06, east of the First Meridian (see McKercher and Wolf, 1986 for more information).
3 Areas are approximate and represent the area of the site boundary and not necessarily the area of critical habitat.
4 Land Tenure is provided as an approximation of land ownership and should be used for guidance purposes only. Accurate land tenure will require cross referencing critical habitat boundaries with surveyed land parcel information.
|No.||Site Name1||NTS Map|
(1: 50 000)2
|Latitude and Longitude representing the Site3||Area (ha)4||Description||Land Tenure5|
|1||Arkell – Corwhin Wetland Complex||40P09||43.539;|
|79||South of Eden Mills||Non federal|
|2||Big Creek NWA, Crown Marsh, Long Point Provincial Park||40I09||42.586; |
|1216||West end of Long Point Sandspit||Federal (NWA), Non federal|
|3||Big Rice Bay Marsh – Thoroughfare Unit, Long Point NWA||40I09||42.586; |
|405||Big Rice Bay Marsh area of Thoroughfare Unit||Federal (NWA), Non federal|
|4||Big Sand Bay||30N15||43.922; |
|141||West of Prince Edward Point National Wildlife Area||Non federal|
|5||Birdsalls Creek||31D08||44.288; |
|79||South of Westwood||Non federal|
|6||Cooper Marsh||31G02||45.108; |
|79||West of South Lancaster||Non federal|
|7||Hoards Creek||31C05||44.276; |
|79||South of Hoards||Federal (PCA), Non federal|
|8||Hullett Marsh Complex||40P11||43.631; |
|137||East of Clinton||Non federal|
|9||Hutton Creek Wetland||31C16||44.789; |
|79||West of Motts Mills||Non federal|
|10||Indian Creek Wetland||40I09||42.658; |
|1132||West of Turkey Point||Non federal|
|11||Little Rice Bay Marsh – Thoroughfare Unit, Long Point NWA||40I09||42.586; |
|134||Little Rice Bay Marsh area of Thoroughfare Unit||Federal (NWA)|
|12||Loch Garry||31G07||45.27; |
|79||South of Greenfield||Non federal|
|13||Long Point Unit – Long Point NWA||40I09||42.557; |
|1036||Along north shoreline of Long Point Unit||Federal (NWA)|
|14||Luther Marsh||40P16||43.928; |
|79||East part of Luther Marsh Conservation Area||Non federal|
|15||Marysville Creek Wetland||31C03||44.178; |
|127||East of Big Bay||Federal (First Nations)|
|16||Matchedash Bay Wetland (SE11)||31D12||44.768; |
|111||North end of wetland||Federal (PCA), Non federal|
|17||Miller Creek Wildlife Area||31D08||44.385; |
|79||Miller Creek Wildlife Area||Non federal|
|18||Mississippi River Snye||31F08||45.462; |
|79||South of Fitzroy Harbour||Non federal|
|19||Mud Creek||31F11||44.737; |
|134||West of North Augusta||Non federal|
|20||Parks Creek||31C06||44.293; |
|79||South of Halston||Non federal|
|21||Presqu'ile Bay Marsh 1||31C04||43.996; |
|297||Middle section of Presqu'ile Provincial Park||Non federal|
|22||Presqu'ile Bay Marsh 2||31C04||44.013; |
|79||North end of Presqu'ile Provincial Park||Non federal|
|23||Rankin River Wetland||41A14||44.793; |
|89||South of Sky Lake Management Area||Non federal|
|24||Rondeau Provincial Park||40I05||42.278; |
|158||West side of Rondeau Provincial Park||Non federal|
|25||Ross Lake Wetland||31C06||44.317; |
|99||North of Madoc Junction||Non federal|
|26||Sandbanks Provincial Park||30N14||43.889; |
|79||Southeast section of Sandbank Provincial Park||Non federal|
|27||Snelgrove Brook||31D08||44.394; |
|79||East of Bridgenorth||Non federal|
|28||St. Clair Marsh Complex||40J08||42.453; |
|79||Middle section St. Clair Marsh||Non federal|
|29||St. Clair NWA Marsh Complex – Bear Creek Unit||40J09||42.534; |
|173||St. Clair NWA – Bear Creek Unit||Federal (NWA), Non federal|
|30||St. Clair NWA Marsh Complex – St. Clair Unit||40J08||42.363; |
|665||St. Clair NWA – St. Clair Unit||Federal (NWA), Non federal|
|31||Sturgeon Bay Marsh||31D12||44.733;|
|101||Southwest end of the Trent Severn Waterway||Federal (PCA), Non federal|
|32||Sturgeon Lake No. 26||31D07||44.403; |
|104||North of Lindsay||Federal (PCA), Non federal|
|33||The Swale Wetland||31C16||44.888; |
|79||West of Smiths Falls||Federal (PCA), Non federal|
|34||Thrashers Corners Wetland||31C16||44.274; |
|115||Northeast of Thurlow||Non federal|
|35||Tiny Marsh (Ti7)||31D12||44.59; |
|304||Northeast of Allenwood||Non federal|
|36||Unnamed Wetland – City of Quinte West||31C03||44.171; |
|88||Northeast of Johnstown||Non federal|
|37||Unnamed Wetland – Haldimand–Norfolk County||40I09||42.604; |
|79||East of Long Point Road||Non federal, Federal (NWA)|
|38||Unnamed Wetland 1 – City of Prince Edward County||30N14||43.874; |
|97||East of Point Petre Militaries Reserves Site||Non federal|
|39||Unnamed Wetland 2 – City of Prince Edward County||31C03||44.161; |
|79||North of Solmesville||Non federal|
|40||Upper Canada Migratory Bird Sanctuary||31B14||44.955; |
|79||Upper Canada Migratory Bird Sanctuary||Non federal|
|41||Wenona Marsh||31D14||44.791; |
|79||South of Gravenhurst||Non federal|
|42||Wheatley East Two Creeks||40J01||42.083; |
|79||Wheatley Provincial Park||Non federal|
|43||Woodview Swamp||31D08||44.327; |
|79||West of Jermyn||Non federal|
|44||Wye Marsh (TA2)||31D12||44.707; |
|316||Southwest section of Wye Marsh||Non federal|
1 Names are derived from Ontario Ministry of Natural Resources, Evaluated Wetland Boundaries (Land Information Ontario) and from the Great Lakes Coastal Wetland Consortium, Coastal Wetland Database (Great Lakes Commission) where available. Unevaluated or unnamed wetlands are identified by the township in which they reside. In many cases, only a portion of the wetland contains critical habitat.
2 National Topographic System.
3 The listed coordinates represent the southwest corner of the 1 km Universal Transverse Mercator (UTM) Military Grid Reference System square containing the critical habitat site centroid, see for more information on the reference system. The coordinates may not fall within critical habitat and are provided as a general location only.
4 Areas are approximate and represent the area of the critical habitat site boundary and not necessarily the area of critical habitat.
5 Land Tenure is provided as an approximation of land ownership and should be used for guidance purposes only. Accurate land tenure will require cross referencing critical habitat boundaries with surveyed land parcel information. NWA = National Wildlife Area; DND = Department of National Defence; PCA = Parks Canada Agency.
|No.||Site name||NTS Map (1:50,000)1||Latitude and longitude of site centroid||Area (ha)2||Description||Land tenure3|
|1||Lac La Pêche||31F09||45.635;|
|12||North of the city of Gatineau; within Gatineau Park||Federal (NCC)|
|2||Baie McLaurin Ouest||31G05||45.485; |
|152||East of the city of Gatineau||Non federal|
|3||Marais McLaurin Est||31G05 and 31G12||45.493;|
|212||East of the city of Gatineau||Non federal|
|4||Marais aux Massettes||31G11||45.577;|
|99||Managed wetland Eats of the city of Gatineau||Non federal|
|5||Marais aux Grenouillettes||31G12||45.510; |
|40||Managed wetland Est of the city of Gatineau||Non federal|
|6||Marais des Laîches||31G12 and 31H05||45.503;|
|79||East of the city of Gatineau||Non federal|
|7||La Grande Baie |
(Oka provincial park)
|31G08 and 31H05||45.485;|
|79||In Oka provincial Park||Non federal|
|8||Grand marais de Beauharnois||31H05||45.266;|
|102||Managed wetland in Beauharnois||Non federal|
|9||Marais de Beauharnois N–O et S–O – Étang 1||31H05||45.268; |
|79||Managed wetland in Beauharnois||Non federal|
|10||Marais de Beauharnois N–O et S–O – Étang 2||31H05||45.279;|
|159||Managed wetland in Beauharnois||Non federal|
|213||Managed wetland in Chateauguay||Non federal|
|12||Île des Soeurs||31H05||45.454; |
|8||On Nun’s island in the city of Montréal||Non federal|
|23||West of Chateauguay||Non federal|
|14||Parc–nature du Bois–de–l'île–Bizard||31H12||45.513;|
|12||Regional park in Montreal||Non federal|
|15||Marais du Bois 440||31H12||45.657;|
|9||Wetland in the city of Laval||Non federal|
|16||Île aux Fermiers||31H11||45.666;|
|133||On an island East of Montréal||Federal (other)|
|17||Rivière aux Pins (La Frayère)||31H11||45.642;|
|12||North of Boucherville||Non federal|
|18||Île Tourte Blanche||31H11 and 31H12||45.600; |
|3||Part of a provincial parc on the Îles de Boucherville||Federal|
|19||Pointe à la Meule||31H03||45.227;|
|118||Along the Richelieu river; south of Saint–Jean–sur–Richelieu||Non federal|
|102||Along the Richelieu river; East of l’Île aux noix||Non federal|
|21||Rivière du Sud –A||31H03||45.102; |
|328||East of the Richelieu River near the Quebec/USA border; Downstream portion of the river||Non federal|
|22||Rivière du Sud – B||31H03||45.092; |
|130||East of the Richelieu River near the Quebec/USA border; Upstream portion of the river||Non federal|
|23||Anse à l'Esturgeon||31 H03||45.113;|
|118||Along the Richelieu river; south of l’Île aux noix||Non federal|
|94||Along the Richelieu river at the Quebec/USA border||Non federal|
|25||Baie Missisquoi (rivière aux Brochets)||31H03||45.079;|
|170||North of Lake Champlain||Non federal|
|26||Ruisseau Black |
|122||North of Lake Champlain||Non federal|
|27||Farnham (base militaire 7B)||31H06||45.310;|
|10||North of Farnham||Federal (DND)|
|28||Farnham (base militaire 6B)||31H06||45.318;|
|17||North of Farnham||Federal (DND)|
|29||Marais de l’Estriade||31H07||45.400;|
|79||East of Granby||Non federal|
|30||Marais de la rivière aux cerises||31H08||45.279;|
|140||In Magog||Non federal|
|31||Marais Réal–D. Carbonneau||21E05||45.419;|
|11||Managed wetland in Sherbrooke||Non federal|
|32||Île du Moine||31I02||46.094;|
|122||Managed wetland on an island East Sorel–Tracy||Federal (other)/|
|33||Île des Barques||31I02 and 31I03||46.078;|
|51||Managed wetland on an island East of Sorel–Tracy||Federal|
|34||Marais de la Commune||31I02||46.138;|
|31||Managed wetland East of Sorel–Tracy||Non federal|
|143||West of Sorel–Tracy||Non federal|
|36||St–Barthélémy (bassin Ouest)||31I03||46.177;|
|18||Managed wetland south of Saint–Barthélémy||Non federal|
|37||St–Barthélemy (bassin Est)||31I03||46.179;|
|27||Managed wetland south of Saint–Barthélémy||Non federal|
|297||East of Sorel–Tracy||Non federal|
|39||Étangs aménagés de Baie–du–Febvre||31I02||46.153; |
|317||Managed wetland West of Nicolet||Federal (DND)|
|91||Northern portion of the wetland East of Sorel–Tracy||Non federal|
|41||Marais Provencher||21L12||46.720; |
|19||Managed wetland in Neuville||Non federal|
|42||Grande Ferme / Cap Tourmente||21M02||47.051;|
|3||Managed wetland in Cap Tourmente NWA||Federal (NWA)|
1 National Topographic System.
2 Areas are approximate and represent the area of the site boundary and not necessarily the area of critical habitat.
3 Land Tenure is provided as an approximation of land ownership and should be used for guidance purposes only. Accurate land tenure will require cross referencing critical habitat boundaries with surveyed land parcel information. NWA = National Wildlife Area; DND = Department of National Defense; NCC = National Capital Commission.
|No.||Site name||NTS Map (1:50,0001||New Brunswick Breeding Bird Atlas block reference2||Latitude and longitude of site centroid||Area (ha)3||Description||Land tenure4|
|1||Bell Marsh||21I02||NB Atlas p. 65|
Squares B4, B5
|79||The Bell Marsh borders the north shore of the Petitcodiac river and is situated south of Marsh Junction near Moncton.||Non federal|
|2||St. George’s Marsh||21G02||NB Atlas p. 90|
|79||The St. George marsh is located in St. George and borders the Trans Canada highway.||Non federal|
1 National Topographic System.
2 Reference number consists of the page number and block(s) where the critical habitat is located as identified in the 2002 edition of the New Brunswick Atlas (Province of New Brunswick, 2002).
3 Areas are approximate and represent the area of the site boundary and not necessarily the area of critical habitat. The area is the same for each site as there is only one observation per site for the New Brunswick data.
4 Land Tenure is provided as an approximation of land ownership and should be used for guidance purposes only. Accurate land tenure will require cross referencing critical habitat boundaries with surveyed land parcel information.
A strategic environmental assessment (SEA) is conducted on all SARA recovery planning documents, in accordance with the Cabinet Directive on the Environmental Assessment of Policy, Plan and Program Proposals. The purpose of a SEA is to incorporate environmental considerations into the development of public policies, plans, and program proposals to support environmentally sound decision–making.
Recovery planning is intended to benefit species at risk and biodiversity in general. However, it is recognized that recovery strategies may also inadvertently lead to environmental effects beyond the intended benefits. The planning process based on national guidelines directly incorporates consideration of all environmental effects, with a particular focus on possible impacts upon non–target species or habitats. The results of the SEA are incorporated directly into the recovery strategy itself, but are also summarized below in this statement.
The Least Bittern's preference for a combination of dense emergent vegetation interspersed with areas of relatively deep open water, often in remote portions of extensive marshes means that protection of its habitat is largely synonymous with general wetland protection, which would benefit several wetland species (e.g., waterfowl, marsh birds, shorebirds) that use these wetlands for foraging, breeding, staging, resting and/or moulting at certain periods of their annual cycle. Maintenance of the hemi–marsh conditions that Least Bitterns prefer is generally consistent with approaches to enhancing waterfowl and marsh bird habitat (Post and Seals, 2000: Tori et al., 2002; Rehm and Baldassarre, 2007a).
It should be recognized, however, that several other species at risk including birds (King Rail (Rallus elegans), Yellow Rail (Coturnicops noveboracensis) and Prothonotary Warbler (Protonotaria citrea)), fishes (Lake Chubsucker (Erinyzon sucetta), Spotted Gar (Lepisosteus oculatus), Pugnose Shiner (Notropis anogenus)), turtles (Blanding's Turtle (Emydoidea blandingii), Spotted Turtle (Clemmys guttata)) and snakes (Eastern Foxsnake (Clemmys guttata)) may prefer other types of wetland conditions than Least Bitterns. Management actions should take these competing needs into account, while also recognizing the potential for synergistic recovery actions. Wherever possible, natural ecosystem processes should be maintained and allowed to evolve without human interference as these are the processes that marsh inhabitants are naturally adapted to.
The possibility that the present recovery strategy inadvertently generates negative effects on the environment and on other species was considered. The majority of recommended actions are non–intrusive in nature, including surveys and outreach. We conclude that the present recovery strategy is unlikely to produce significant negative effects.
1 COSEWIC = Committee on the Status of Endangered Wildlife in Canada
2 Such predators may also be more abundant that previously because of subsidized feeding opportunities around human settlements.
3 Permanent wetlands include naturally occurring wetlands as well as artificially created wetlands (i.e., impoundments) managed for the purpose of wetland habitat restoration and/or wildlife conservation where water depth may be managed to simulate natural water level fluctuations.
4 This criterion is used to identify a probable breeder within the Quebec Conservation Data Center and was recommended by the National Least Bittern Recovery Team in 2009 as a selection criterion for the present recovery strategy.
- Date Modified: