Department of biology, chemistry and geography
Dominique Berteaux (Regular member)
Joël Bêty (Regular member)
Introduction: Predation is one of the most important selective forces affecting the nesting success of birds. In the High Arctic, some avian species use a proactive strategy against predation by nesting primarily on islets scattered in ponds across the tundra. The islets provide a refuge from predation by Arctic foxes, which are the primary terrestrial predator at the circumpolar scale. Islets farthest from shore and separated from shore by the greatest water depths are selected, but the reason for this selection remains unclear. It is possible that these islets provide the greatest level of protection from predation. However, the risk of nest predation on islets with different physical characteristics remains understudied. Similarly, it is uncertain whether this relative risk may also vary with the abundance of the Arctic fox's primary prey. Objectives: My project aims to better understand the effect of physical characteristics of islets, in interaction with annual densities of Arctic fox primary prey, on the risk of nest predation by Arctic foxes. To do this, I will quantify 1) predation rates on artificial nests experimentally placed on islets, and 2) hatching success of Cackling Geese and Glaucous Gulls nesting on islets with varying physical characteristics. Study sites: The study area is located on the southern plain of Bylot Island (73° N, 80° W) in Sirmilik National Park of Canada. The food web dynamic is controlled by predation, with the Arctic fox being the main terrestrial predator. During the summer, the Arctic fox feeds primarily on lemmings and Greater Snow Geese (especially eggs and young). However, the Arctic fox has several other alternative prey, as more than 35 species of birds nest on Bylot island during the summer. In addition, about 350 islets are georeferenced in the study area, a majority of which are not occupied by birds during the summer. Glaucous Gulls and Cackling Geese are among the primary species selecting islets for nesting. Material and methods: For my objective 1), I will conduct an artificial nest experiment in the wild during the incubation period of the birds. This experiment will isolate the predation mechanism by Arctic foxes for islets with different physical characteristics. One hundred replicated experiments have been carried out in 2022 and another 100 will be carried out in 2023. For my objective 2), I will use hatching success data for Glaucous Gull and Cackling Goose eggs obtained from inventories conducted in the study area in 2018, 2019, 2022, and 2023. I will distinguish the hatching success of these two avian species based on the physical characteristics of the islets on which they nest. Then, for both of my objectives, I will obtain annual densities of foxes' primary prey from lemming live trapping and from Greater Snow Goose nest tracking in random plots. Expected results: When Arctic fox primary prey are abundant, I expect that increasing the distance to the shore and water depth between the islet and shore will decrease the predation rate of artificial nests and increase the hatching success of Cackling Geese and Glaucous Gulls. However, when Arctic fox prey are scarce, I expect that increasing the distance to the shore and the water depth between the islet and the shore will have little or no impact on the predation rate of artificial nests and hatching success of Cackling Geese and Glaucous Gulls.
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