Mallory, Mark L.

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  • Data package
    Data 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 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.