Browsing by Author "Davis, Shanti E."
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- Data packageData from: Migratory connectivity at high latitudes: Sabine’s gulls (Xema sabini) from a colony in the Canadian High Arctic migrate to different oceans(2016-12-14) Davis, Shanti E.; Maftei, Mark; Mallory, Mark L.The world's Arctic latitudes are some of the most recently colonized by birds, and an understanding of the migratory connectivity of circumpolar species offers insights into the mechanisms of range expansion and speciation. Migratory divides exist for many birds, however for many taxa it is unclear where such boundaries lie, and to what extent these affect the connectivity of species breeding across their ranges. Sabine’s gulls (Xema sabini) have a patchy, circumpolar breeding distribution and overwinter in two ecologically similar areas in different ocean basins: the Humboldt Current off the coast of Peru in the Pacific, and the Benguela Current off the coasts of South Africa and Namibia in the Atlantic. We used geolocators to track Sabine’s gulls breeding at a colony in the Canadian High Arctic to determine their migratory pathways and wintering sites. Our study provides evidence that birds from this breeding site disperse to both the Pacific and Atlantic oceans during the non-breeding season, which suggests that a migratory divide for this species exists in the Nearctic. Remarkably, members of one mated pair wintered in opposite oceans. Our results ultimately suggest that colonization of favorable breeding habitat may be one of the strongest drivers of range expansion in the High Arctic.
- Data packageData from: Study "Marbled Murrelet satellite tracking data from British Columbia, Canada 2014-2016"(2022-11-15) Bertram, Douglas F.; Janssen, Michael H.; Cragg, Jenna L.; Macdonald, Christie A.; McAdie, Malcolm; Wilson, Amy; Woo, Kerry; Gross, Eric; Maftei, Mark; O'Hara, Patrick D.; Davis, Shanti E.; Greene, Randall; Vincent, PaolaKnowledge of patterns of seasonal movements are required to inform examinations of the distribution and abundance of marine birds to support conservation efforts. We deployed solar satellite transmitters to track the movements of Threatened Marbled Murrelet (Brachyramphus marmoratus) during the breeding and post breeding periods. We tagged birds in British Columbia, Canada, over three years (2014-2016, n=27), from three different Marbled Murrelet conservation regions defined by the species Recovery Strategy. The tags revealed some local movements of birds during the breeding season but transmissions were limited for the majority of deployments. The tags were most useful in revealing long distance of movements of birds following reproductive attempts. In all three years birds from B.C. moved to Alaska in the post breeding period. In 2014, a murrelet from the Northern Mainland Coast conservation region (Kitimat) travelled to waters near Kodiak Island in August. In 2015, a bird from the South Mainland Coast conservation region (Desolation Sound) travelled to Glacier Bay in July, a known hotspot for Brachyramphus murrelets in summer. In 2016, a bird from the West and Northern Vancouver Island conservation region (Clayoquot Sound) moved to the Alaskan panhandle, reaching the Alexander Archipelago in early August. Our study coincided with the largest Marine Heat Wave recored in the North East Pacific. Birds appeared to track cold water, likely seeking forage fish prey to fuel prebasic molt. Historical and ongoing time series counts of murrelets in Alaska show swelling of numbers in July and August, consistent with the timing of arrival of BC birds, and suggests that our results reflect an annual molt migration dispersal pattern which is not unique to our study period. The arrival of BC birds in Alaska also coincides with the timing of salmon gill net fisheries and thus presents entanglement mortality risk to murrelets in areas of known overlap, such as Kodiak Island. Our tracking work demonstrates strong connectivity between Alaskan and Canadian populations.