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.

Coccidian parasites from birds at rehabilitation centers in Portugal, with notes on Avispora bubonis in Old World

Portugal has some rehabilitation centers for wild animals, which are responsible for the rehabilitation and reintroduction of birds, among other animals, into the wild. Coccidian parasites of these wild birds in rehabilitation centers are especially important because these centers can introduce coccidian species into new environments through the reintroduction of their respective hosts. In this context, the current study aimed to identify intestinal coccidia from wild birds at two rehabilitation centers for wild animals located in two municipalities of Portugal. Eighty-nine wild birds of 9 orders and 11 families were sampled, of which 22 (25%) were positive for Coccidia. Avispora spp. were found in raptors. Sporocysts of Sarcocystinae subfamily were recovered from owls. An Isospora sp. was found in Turdus merula Linnaeus, 1758, and an Eimeria sp. was found in Fulica atra Linnaeus, 1758. Among the coccidian species, Avispora bubonis (Cawthorn, Stockdale, 1981) can be highlighted. The finding of this species indicates that transmission of coccidians from the New World to the Old World may be occurring, potentially through dispersion by Bubo scandiacus (Linnaeus, 1758) through Arctic regions or by means of anthropic activities, and/or through other unknown mechanisms.