Effects of Weather On Foraging Success and Hunting Frequency In Winter-Irruptive Snowy Owls (Bubo scandiacus) In Upstate New York

ABSTRACT The effects of weather on an individual can often alter the population dynamics of a species. Knowledge of how weather influences individual behavior is therefore essential in understanding its full impact in the context of population ecology. Snowy Owls (Bubo scandiacus) exhibit expensive long-distance migrations in winters following population irruptions. During irruptive movements, many owls migrate past the southernmost extent of their traditional wintering grounds, the mechanism for which is still debated. We propose and test the “milder climate” hypothesis; Snowy Owls wintering in lower latitudes are better able to meet their metabolic demands due to higher temperatures and lower snow cover. During the Snowy Owl irruption of 2014–2015, we examined this hypothesis by assessing the influence of local weather variables on foraging success, frequency of prey capture attempts, and overall activity budgets in a sample of wintering Snowy Owls in New York, USA. We used eBird, an online citizen science resource, to help locate Snowy Owls, which we observed from an automobile. We found that none of the weather variables tested affected foraging success. However, the lack of effect of snow depth on foraging success may suggest that hearing is more important for hunting in Snowy Owls than previously thought. Hunting frequency decreased with increasing temperatures, suggesting Snowy Owls were better able to meet their metabolic demands in higher temperatures. We thus offer support for the milder climate hypothesis; Snowy Owls wintering in lower latitudes may be able to offset the energetic expenses of long-distance movements.

The Snowy Winter

This chapter describes the author's experience while staying on Cape Cod to finish a novel. The best moment came when the author was standing alone out on Coast Guard Beach — on almost the exact spot where the naturalist-writer Henry Beston lived for a year in his outermost cabin on Cape Cod's ocean shore — when the young snowy owl rose off the tundra-like marsh with a black duck in its talons. The duck hung down limp below the owl, and below that the duck's lifeless feet hung down even lower, like damaged landing gear. The author saw a couple who attempted to follow the owl. The couple were not birders, but they were considerate, giving the owl plenty of space. “Radiant” is a word the author had been using a lot during their last few days of owl-watching, though mostly to describe the white unworldly shine of the snowy owl's feathers.