Short-eared Owl Asio Flammeus Research Articles

Continuous light and physiology of Arctic birds and mammals.

Many investigations of pineal function have been conducted on animals experiencing artificial laboratory environments. The use of species that naturally experience extreme conditions, such as constant light or darkness, is suggested as a possible way to clarify some of the confusion that exists in the pineal literature at the present time. Arctic species are adapted to an environment in which conditions of constant light are naturally replaced with periods of alternating light. Other conditions of the arctic also vary, including temperature, wind, precipitation, available food, and inter- and intra-species interactions. Arctic species must be highly attuned to their harsh environment. Four species of arctic homeotherms have particular promise as models for the study of pineal function: Snowy owls (Nyctea scandiaca ) and short-eared owls (Asio flammeus ), in contrast with most other owls, must annually switch from being day-active to being at least partially night active. The Arctic fox (Alopex lagopus ) shows regular circannual variations in several parameters alleged to be under the influence of the pineal in other species, including reproduction, activity levels, and seasonal molts. Lemmings (Lemmus trimucronatus ) have two periods of reproductive activity per year, one at the height of the constant light season, and a less intense period that coincides with minimal light. Hormonal activity and possibly pineal activity in lemmings is also implicated in periodic, large scale population fluctuations.

Observations Concerning Behavior, Feeding, and Pellets of Short-Eared Owls

A wintering flock of short-eared owls (Asio flammeus) was observed in southern Michigan during March and April 1960. Observations of daily activity, hunting behavior and feeding habits are presented. A statistical analysis of the pellets of short-eared owls is included. This analysis emphasizes the relationship between pellet size and meal size and between pellet size and the skeletal components within the pellet. iwc;:orare offered about the interpretation of animal remains found in the pellets of short-eared owls. During the winter season flocks of short-eared owls, Asio flammeus, congregate at suitable sites throughout the Great Lakes region. During March and April of 1960, we observed such a flock which roosted on a farm four miles south of Williamston, Ingham County, Michigan. This paper reports observations on hunting and feeding behavior and feeding data which aid in the analysis of the pellets of short-eared owls. We are grateful to Mr. Kenneth Kurtz who told us of the presence of the owls and who extended many courtesies to us throughout this investigation. We are also indebted to Dr. Ulreth Mostosky, of the Department of Surgery and Medicine, Michigan State University, for his X-ray of a series of owl pellets and to Henry W. Klippell for assistance with photographs.

A STUDY OF THE WINTER FEEDING HABITS OF THE SHORT-EARED OWL (Asio flammeus) IN THE TORONTO REGION

The winter feeding habits of the short-eared owl (Asio flammeus Pontoppidan) were studied during the period of 1936 to 1942 in the vicinity of Toronto, Ont. The owls used restricted roosts in several groups of Douglas fir (Pseudotsuga taxifolia) on a golf course. By means of frequent owl population censuses and collection of pellets, food requirements and correlations were calculated.The winter incursions of the owls were found to be cyclic and to coincide with the local meadow vole (Microtus pennsylvanicus) cycle and to be independent of meteorological factors. Roosting behaviour was found to vary with snow cover.From an analysis of 3000 pellets it was found that the meadow vole formed 82% of the food taken. The next animal most commonly preyed upon was the deer mouse (Peromyscus leucopus), which comprised 17% of the food, while birds formed 1%. No significant seasonal change in diet was noted over a period of five months.It was calculated that a short-eared owl eats between 700 and 1600 mice per year. The average figure is thought to be nearer the minimum estimate. Translated to weight of mice this is equivalent to between 55.5 and 127 lb.It was demonstrated that the amount of snow on the ground affected the relative availability of meadow voles and deer mice. This fact was reflected in changes in pressure on the populations of the two mice species due to owl predation.The data presented pointed to the possibility that concentrations of avian predators could have an appreciable effect on local meadow vole populations. In the case under study it was estimated that winter short-eared owl predation might account for 10% of the vole population.The data also suggested that during periods of deep snow, because of decreased availability of meadow voles, less food is taken and during open periods increased availability of these mice is reflected by increased food consumption.

The Short-Eared Owl (Asio flammeus flammeus) in the District of Columbia

The Short-Eared Owl (Asio flammeus flammeus) in the District of Columbia

Short-Eared Owl (Asio flammeus) Eating Birds

Short-Eared Owl (Asio flammeus) Eating Birds

Short-eared Owl (Asio flammeus) Eating Birds

Short-eared Owl (Asio flammeus) Eating Birds