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Allard, Karel A.

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Allard
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Karel A.
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  • Data package
    Data from: Study "American Herring Gulls - GPS - Lobster Bay, Southwest Nova Scotia, Canada"
    (2023-08-29) Mallory, Mark L.; Craik, Shawn; Allard, Karel A.; Gutowsky, Sarah
    Anthropogenic food subsidies attract opportunistic generalists like gulls in high densities, which may lead to negative impacts on human communities and local ecosystems. Managing impacts requires understanding why gulls use particular natural or industrial sites at different times of day or phases of the breeding cycle. Use of natural and human-influenced habitats likely varies temporally as gulls alter schedules and site selection to match the predictability of different resources as they vary through space and time relative to patterns in human activities and natural rhythms, whilst gull resource requirements and restrictions to movement also shift with changing reproductive demands. We quantified seasonal and circadian patterns in American herring gull interactions with anthropogenic and natural sites throughout breeding using GPS data from 15 gulls tracked over three years. We examined the weekly probability of gull occurrence at distinct destinations (e.g., islands, offshore, fish processing plants), and how occurrence varied with time of day, weekday/weekend, and tide phase, using GLMMs with a binomial response for destination-specific occurrence. Probability at the colony varied predictably through the breeding season (highest attendance from dusk to dawn, during incubation and early chick rearing), providing confidence in the modelling approach for detecting temporal patterns in behaviour. Gulls visited other islands mostly outside incubation and chick rearing, from dusk through night, likely roosting. Occurrence offshore where interaction with fishing vessels is possible was highest from dusk to dawn, but was the most likely destination during incubation and early chick rearing. Occurrence at fish plants gradually increased until after fledging when attendance was highest from Aug-Oct coincident with the peak of Atlantic herring processing, and was more likely during the weekdays, during working hours, and during low and flood tide. Gulls in southwest Nova Scotia, Canada, have the behavioural flexibility to adapt to natural rhythms and human schedules when beneficial, enabling them to thrive in a region where industry and natural resources are abundant. These findings can provide information to guide when and where to test different subsidy management strategies locally, while also considering potential increased pressures on island ecosystems.
  • Data package
    Data 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.