COMPARATIVE DIET ANALYSIS OF BARN OWL (TYTO ALBA) AND LONG- EARED OWL (ASIO OTUS) IN A HABITAT ISLAND IN NORTH-CENTRAL TEXAS

Abstract

Abstract Predator-prey interactions often define the coexistence of species in space and time. In this research, we are filling a regional gap in knowledge of diet composition of the barn owl (Tyto alba) and the long-eared owl (Asio otus). The study was conducted at the Lewisville Lake Environmental Learning Area (LLELA), a patch of tallgrass prairie and post oak forest surrounded by areas with large anthropogenic modifications in north-central Texas. We examined the remains found in owl pellets collected September 2016 to March 2017. Small mammals, mainly rodents, constituted 100% of the T. alba and 98.5% of the A. otus diet. The hispid cotton rat (Sigmodon hispidus) was the most common prey detected (68.2% for T. alba and 89.0% for A. otus). Diet niche breadth of T. alba was broader than that of A. otus (0.47 and 0.06, respectively), whereas mean prey size was smaller in the T. alba diet. Diet overlap between these owls was high (0.96), likely because they hunt similarly at night, on the wing, and the prey species have limited diversity. Most rodents eaten were juveniles and the sex ratio of prey was even in both owls’ diets. We highlight the value of conducting studies in such a unique and relatively pristine environment in the face of multiple threats. Additionally, although the occurrence of A. otus is rare and infrequent in the study area, we were still able to detect a difference in diet between the ubiquitous T. alba and A. otus.