The Winter Foods of Some Indiana Owls

The well-known writings of Errington and his colleagues on predator-prey relationships, summarized by the great horned owl report (Errington et at, 1940), are so comprehensive that little can be added to the subject particularly as regards the food habits of owls based upon pellet analyses. Nevertheless, the present report may be of general interest since it demonstrates the emphasis received by a single prey species, Microtus o. ochrogaster,* from four species of owls occurring in Tippecanoe County, Indiana. The fall and winter of 1946-47 have been seasons of ochrogaster abundance if not peak population levels. Irrespective of the different habits of the four owl species, their foraging has carried them universally into the habitat of ochrogaster which was the %most frequently encountered prey item in the pellets of all owls, although in total bulk this prey may not be the greatest in case of the great horned owl. The data reported here are of particular local interest in view of the dearth of facts regarding the food habits of Indiana raptors. The information will be useful in the defense of raptors which are sometimes unjustly persecuted due to public misuderstanding concerning the effect of raptors on agricultural activities and upon populations of small game. The discovery of roosting sites of long-eared owls, short-eared owls, and great horned owls within the space of a few weeks led us to exploit these sources of pellet material. All pellets excepting some from the barn owl were collected during the winter of 1946-47. The technique of analysis was in general that described by Errington (1930). Some specific methods are included under the owl species discussed.