Pink-footed shearwater (Puffinus creatopus) COSEWIC assessment and status report: chapter 5

Habitat

Habitat requirements and trends

Breeding

The Pink-footed Shearwater nests in long, twisting burrows that can penetrate a few metres underground, making it impossible to detect the actual nest chamber from the outside. On Isla Mocha, the species breeds in colonies in dense forest, from about 150 m above sea level and up into the mountain ridges (Guicking 1999, Guicking et al. 2001). The main colony is located just above a village on the east side of the island (Guicking 1999). Burrows are often destroyed by harvesters when collecting chicks (see sections below).

On Robinson Crusoe, the main Pink-footed Shearwater colony is located along a ridgeline. On Santa Clara, burrows are scattered over extensive parts of the island, with several groups of 100-300 each, but also many solitary ones (Guicking and Fiedler 2000). At both locations, burrows are located in open terrain with grassy vegetation. It is likely however, that the breeding habitat on Robinson Crusoe was once heavily forested. With active deforestation and the introduction of herbivores (including sheep, cattle, horses, donkeys, and goats) prior to and during the 20th century (Hahn and Römer 2002), many forested areas have been greatly reduced on this island (Bourne et al. 1992, Hahn and Römer 2002). Storms and periods of heavy rain tend to impact burrows in these locations to a greater extent than those in vegetated areas (Hodum and Wainstein 2002). Introduced rabbits (Oryctoloagus cuniculus) occur in large numbers on both Robinson Crusoe and Santa Clara, and their presence strongly contributes to the loss of vegetation and hence erosion (Bourne et al. 1992, Guicking and Fiedler 2000, Hahn and Römer 2002). There is also a suggestion that rabbits compete with Pink-footed Shearwaters for breeding burrows (Schlatter 2002, Hodum and Wainstein 2002, 2003).

Marine

Results from the satellite tracking of a small number of breeders and non-breeders from the Isla Mocha colony in 1999 indicate that Pink-footed Shearwaters show a strong preference for travelling and feeding close (within 1 km) to the mainland coast during the breeding season (Guicking et al. 2001). The study revealed a major inshore foraging area 250-300 km north of the colony, and a second potential area approximately the same distance south. The observed sites coincided with areas of high abundance of sardines and anchovies, the main component of the Pink-footed Shearwater diet during the breeding season. Associated oceanographic conditions included highly saline waters, and stable sea-surface temperatures of 14-18°C (Guicking et al. 2001).  Brown et al. (1975) recorded the presence of Pink-footed Shearwaters in association with similar oceanographic conditions off Chile during the summer. Results from a satellite tracking investigation on Santa Clara, in the Juan Fernandez group, indicated foraging areas approximately 70-258 km to the northeast and southeast of the colony during the 2002 breeding season (Hodum and Wainstein 2002). In contrast, during the 2003 season, breeding adults were recorded travelling much farther distances (from 315-650 km) to the east of Santa Clara. These results indicate interannual differences in foraging behaviour, and investigations of related oceanographic and dietary factors are ongoing (Hodum and Wainstein 2003).

While few in number, possibly the result of reduced observer effort at this time, winter sightings of the Pink-footed Shearwater off the coast of Chile are also associated with sea-surface temperatures of 14-18°C (Jehl 1973). It is unknown if these sightings were of foraging individuals, or those on the wing.

Very little is known of the specific marine habitat requirements of the Pink-footed Shearwater throughout the species’ winter range. In general, the post-breeding distributions of the Pink-footed Shearwater in North America appear to be positively associated with the continental shelf (Wahl 1975, Guzman and Myres 1983, Briggs et al. 1987, Vermeer et al. 1989, Morgan et al. 1991, D. Hyrenbach pers. comm. 2003), and with aspects of the California Current system (Ainley 1976, Briggs et al. 1987) which extends as far north as Triangle Island off the coast of British Columbia. In general, these areas are characterized by seasonal periods of upwelling and high biological productivity (Hay 1992).

Off the California coast, the abundance and densities of Pink-footed Shearwaters vary considerably on an annual basis (Ainley 1976, Ainley et al. 1995), and within years shifts according to the phases, and regions of influence, of the California Current system. However, the species tends to be generally associated with temperatures ranging from 14-19°C (Ainley 1976), away from the most intense upwelling (Briggs et al. 1987). The abundance of Pink-footed Shearwaters off California tends to be lower during periods of higher sea-surface temperatures, such as those observed during El Niño events (Ainley et al. 1995). Briggs et al. (1987) speculate that they may be more abundant in the second year following such periods. Ainley (1976) speculated that yearly differences in abundance of Pink-footed Shearwaters off California may be connected to (austral) winter ocean conditions off Peru and Chile. During periods of low anchovy production off the South American coast during this time, Pink-footed Shearwaters may move in greater numbers to the California Current region (Ainley 1976).

Off Washington, the Pink-footed Shearwater occurs almost exclusively over the outer edge of the shelf (Wahl 1975). Again, as with California, the abundance of Pink-footed Shearwaters varies greatly on an annual basis, and also tends to be lower during El Niño events (Wahl and Tweit 2000). Off Vancouver Island and the Juan de Fuca Strait in Canada, the Pink-footed Shearwater is most commonly seen from approximately the outer edge of the shelf, inshore to the 90 m depth contour (Guzman and Myres 1983, Vermeer et al. 1989).

Protection/ownership

Isla Mocha and the Juan Fernandez Archipelago are under Chilean ownership and management. The Pink-footed Shearwater migrates through the waters of Chile, Peru, Ecuador, Colombia, Panama, Costa Rica, Nicaragua, Guatemala, El Salvador, Honduras, Mexico, the United States and Canada (Schlatter 2002). 

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