Spying on Arctic peregrine falcons

Peregrine falcons (Falco peregrinus) are one of the most widely distributed terrestrial vertebrates on the planet inhabiting every continent except Antarctic. Many people do not realize that a subspecies of this magnificent bird of prey (F. p. tundrius) breeds in the Arctic regions of Canada, the USA and Greenland. Arctic peregrine falcons spend the summers breeding on cliffs throughout tundra habitats, then migrate thousands of kilometers to their wintering grounds in Central and South America (e.g. Brazil, Argentina, Mexico, French Guiana).

The climate in the Arctic is changing even more rapidly than at more southern latitudes, which could influence some of the prey populations on which Arctic peregrine falcons rely. Insectivorous songbirds and shorebirds, an important component the Arctic peregrine falcon’s diet, are negatively affected by summer rainstorms, which reduce the activity and abundance of insects for insectivorous birds to forage on. The frequency and severity of summer rainstorms in the Arctic are predicted to increase, which may reduce populations of insectivorous birds. We are currently investigating the foraging ecology of Arctic peregrine falcons in Nunavut, Canada, to predict how changes in prey populations associated with global climate change will affect peregrine falcon diet and reproduction.

To monitor peregrine falcon diet, we installed motion-sensitive cameras (RECONYX) at nest sites to document prey deliveries made to nestlings. Since peregrine falcons nest on large cliffs, we used climbing gear to rappel to nest platforms. Data from these cameras inform us which prey types peregrine falcons are eating and allow us to estimate the relative contribution of each prey type to the overall diet. By relating peregrine falcon diet to fluctuations in prey density and annual weather patterns, we can develop a better understanding of the potential implications of climate change on this top predator.

One disadvantage of using motion-sensitive cameras for monitoring diet is that some prey deliveries are inevitably unidentifiable because of low lighting, poor camera focus, or a blocked field of view. Unidentified prey deliveries, a problem common to all studies using cameras to monitor diet, are generally unaccounted for, which reduces the precision and accuracy of diet estimates. In a paper published recently in Wildlife Biology (Estimating nestling diet with cameras: quantifying uncertainty from unidentified food items), we develop a novel statistical method in which we use unidentifiable prey deliveries to quantify the amount of uncertainty around diet estimates.

This broadly applicable method can be adapted and used for any study monitoring animal diet with cameras. As the technology improves and cameras become smaller and higher in resolution, studies using cameras will likely proliferate. Our method provides researchers with a way to quantify the uncertainty associated with unidentified food deliveries, which has never been addressed before.

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