Ivory gull (Pagophila eburnea) recovery strategy 2014: chapter 11

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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 Destruction of Critical Habitat

7.1 Identification of the Species' Critical Habitat

Ivory Gulls have simple but specialized habitat requirements. Specifically, they require breeding sites that are safe from terrestrial predators (particularly the Arctic Fox, Alopex lagopus), but in proximity (~ 50 km) of open water for feeding (closer than the 100 – 200 km stated in COSEWIC 2006, based on more recent data; M. Mallory, unpubl. data). The biophysical attributes of critical breeding habitat for ivory gulls can be characterized as remote islands, remote polar desert or cliff faces of nunataks in proximity (~50 km) of open water for feeding.

Critical habitat is defined in SARA (Subsection 2(1)) as “the habitat that is necessary for the survival or recovery of a listed wildlife species and that is identified as the species’ critical habitat in the recovery strategy or in an action plan for the species”.

Currently, there is insufficient information on migration, wintering or feeding habitats to identify critical habitat for those locations or part of the species’ annual cycle. Critical habitat for the Ivory Gull is identified in this recovery strategy to the extent possible based on the best available information. It is recognized that the critical habitat identified below is insufficient to achieve the population and distribution objectives for the species. The schedule of studies (Section 7.2) outlines the activities required to identify additional critical habitat necessary to support the population and distribution objectives of the species.

Critical habitat locations were identified based on the following criterion:

1) Colonies where at least one Ivory Gull has been observed nesting at least once from 2002-2009 (since one gull can represent a nesting pair). Ivory Gulls may use colonies in one year, then move to another location in the following year and return to the initial colony in a following year (collectively as a predator avoidance strategy), so all recently occupied sites are considered critical habitat.

For each location identified using the above criterion, a 2-km radius around the approximate centroid of the colony was used as the extent of critical habitat around a colony. Six years of survey work suggests that disturbance within a 2-km radius of the centre of a colony may affect the ability of the Ivory Gulls to use the habitat for nesting.

Critical habitat for the Ivory Gull is identified in this recovery strategy in 39 locations in Nunvut, outlined in Appendix A. These locations are all breeding colonies for Ivory Gulls, either on flat ground (Seymour Island, Cornwallis Island, western Devon Island, Brodeur Peninsula of Baffin Island), or on nunataks (eastern Devon Island, eastern Ellesmere Island). Each colony is identified by a geo-referenced co-ordinate, and the critical habitat includes all land within a 2 km radius of that co-ordinate.

Other locations where Ivory Gulls have been found to occur were not identified as critical habitat at this time as they did not meet the criterion for identifying critical habitat.

There was not sufficient information available for identifying additional critical habitat at the time this document was prepared. Studies to determine additional critical habitat are outlined in Section 7.2. Additional critical habitat will be identified in an action plan following completion of the schedule of studies.

7.2 Schedule of Studies to Identify Critical Habitat

7.3 Activities Likely to Result in Destruction of Critical Habitat

Destruction is determined on a case by case basis. Destruction would result if part of the critical habitat were degraded, either permanently or temporarily, such that it would not serve its function when needed by the species. Destruction may result from a single or multiple activities at one point in time or from the cumulative effects of one or more activities over time (Government of Canada 2009).

Destruction of Ivory Gull critical habitat is any alteration to the breeding colony that can adversely modify the biological, chemical or physical features (e.g., topography, geology, microclimate) to the extent that the critical habitat no longer exists or cannot be used. It should be noted that some activities may not destroy critical habitat initially, but when occurring repeatedly over time or in conjunction with other damaging activities, there can be a destructive effect on critical habitat.

Examples of activities that may result in the destruction of critical habitat include, but are not limited to:

1. Long-term anthropogenic activity near a breeding colony site. Activities that create removal, covering or chronic disturbance of land surface such as building construction, excavation of nesting substrate, industrial activities (e.g., mineral exploration, mine development) can destroy critical habitat by three means. First, activities can directly alter the physical structure and functional integrity of the habitat, rendering it unsuitable or impossible for birds to nest on. Second, establishment of long-term camps near a breeding colony may attract predators (e.g. foxes, corvids) that would not normally frequent the area, which may lead birds to stop choosing this suitable nesting area. Third, spills of petroleum or other pollutants (including garbage) may accumulate around nest sites, rendering them unattractive to nesting.