DIET AND SELECTIVITY OF SPEOTYTO-CUNICULA RIA IN A SEMIARID LOCALITY OF NORTHERN CHILE THROUGHOUT 7 YEARS (1987-1993)

On a seasonal basis, we quantified the diet of Speotyto cunicularia th roughout seven years in a semi-arid locality of northern Chile (Auco). The main numerical component of the diet was insects (79%), specifica lly families in the order Coleoptera (Tenebrionidae, Scarabaeidae, Car abidae, and Curculionidae), and to a lesser extent! arachnids (11%). V ertebrates accounted for only 10% of the total number of prey, but the ir energy contents largely exceeded that of insects and arachnids. Amo ng mammals (6% of total prey), the Murid rodents Phyllotis darwini, Ak odon olivaceus and Oryzomys longicaudatus, and the Didelphid marsupial Marmosa elegans, were the most frequent and constant components in th e diet of the owl. There was a consistent and significant (P < 0.05) u nderconsumption of Akodon longipilis, Chinchilla lanigera, Octodon deg us and P. darwini. However, there was a marginally significant (P < 0. 07) overconsumption of M. elegans. Underconsumed mammals exceeded 45 g on average, whereas overconsumed ones did not exceed 28 g (perhaps wi th exception of juvenile A. bennetti). Thus, there seems to be a maxim um critical prey size that S. cunicularia is capable of handling. Amph ibians made up only 4% of total prey, whereas reptiles and birds appea red only as trace elements (<< 1%). During fall and winter an increase in the consumption of insects generally occurred, whereas during spri ng and summer an increase in the consumption of arachnids and vertebra tes was noted. These results indicate that S. cunicularia is a seasona lly opportunist predator.