Browsing by Author "Macdonald, Christie A."
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- Data packageData from: Study "Herring Gulls (Larus Argentatus); Gilchrist; East Bay Island, Canada"(2020-06-17) Gilchrist, H. Grant; Macdonald, Christie A.; Janssen, Michael H.; Allard, Karel A.; Anderson, Christine M.Background: Recent studies have proposed that birds migrating short distances migrate at an overall slower pace, minimizing energy expenditure, while birds migrating long distances minimize time spent on migration to cope with seasonal changes in environmental conditions. Methods: We evaluated variability in the migration strategies of Herring Gulls (Larus argentatus), a generalist species with flexible foraging and flight behaviour. We tracked one population of long distance migrants and three populations of short distance migrants, and compared the directness of their migration routes, their overall migration speed, their travel speed, and their use of stopovers. Results: Our research revealed that Herring Gulls breeding in the eastern Arctic migrate long distances to spend the winter in the Gulf of Mexico, traveling more than four times farther than gulls from Atlantic Canada during autumn migration. While all populations used indirect routes, the long distance migrants were the least direct. We found that regardless of the distance the population traveled, Herring Gulls migrated at a slower overall migration speed than predicted by Optimal Migration Theory, but the long distance migrants had higher speeds on travel days. While long distance migrants used more stopover days overall, relative to the distance travelled all four populations used a similar number of stopover days. Conclusions: When taken in context with other studies, we expect that the migration strategies of flexible generalist species like Herring Gulls may be more influenced by habitat and food resources than migration distance.
- 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.