Rodents New to the Diet of the Western Burrowing Owl (Athene Cunicularia Hypugaea) (Notes) (Report‪)‬

The western burrowing owl (Athene cunicularia hypugaea) is widespread throughout much of the western United States, south-central Canada, and northern Mexico. Northern populations of the western burrowing owl are migratory and winter in southern Texas and Mexico (Rappole and Blacklock, 1985; Haug et al., 1993). The burrow ing owl is an opportunistic predator that consumes a wide range of invertebrate and vertebrate prey, including a variety of rodents from the families Muridae and Heteromyidae (Haug et al., 1993). Murids that have been recorded as prey of the western burrowing owl include North American deermice and cactus deermice (Peromyscus maniculatus and P. eremicus), house mice (Mus musculus), voles (Microtus and Lagurus), hispid cotton rats (Sigmodon hispidus), grasshopper mice (Onychomys), and harvest mice (Reithrodontomys, Thomsen, 1971; Marti, 1974; Conroy and Chesemore, 1987; Green et al., 1993; Rodriguez-Estrella, 1997). Heteromyids consumed by burrowing owls include kangaroo rats (Dipodomys) and pocket mice (Chaetodipus and Perognathus, Jaksic and Marti, 1981). Here we report identification of remains of the northern pygmy mouse (Baiomys taylon), fulvous harvest mouse (Reithrodontomys fulvescens), and Merriam's pocket mouse (Perognathus merriami) as prey of the western burrowing owl. None of these species had been identified as prey until the winter diet of burrowing owls in southern Texas was examined (Littles et al., 2007). Regurgitated pellets (n = 182) of western burrowing owls were collected from roost sites in southern Texas over 4 winters (1999-2000 and 2001-2004) to determine composition of diet in winter. Six species of rodents and one species of shrew were identified from the pellets (Table 1). The two most abundant species in pellets were the northern pygmy mouse and the fulvous harvest mouse, of which we identified 38 and 31 individuals, respectively. Combined, the number of these two species represented 58% of all mammals that we identified. These species also showed the greatest frequencies of occurrence in pellets (Table 1). Merriam's pocket mouse was a smaller component of the diet, representing only 4% of identified mammals and occurring in 3% of pellets.