Food Habits and Bioenergetics of a Pair of Barn Owls and Owlets

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Abstract
The food habits and bioenergetics of a pair of barn owls (T. alba) were examined for 19 mo. Biomass consumption rates of adults and young were quantified during nesting and nonnesting seasons. Pellets (594) were examined to determine prey species and numbers. Using log-log regressions, biomass consumption of prey individuals was estimated as a function of right mandible length and body wet weight of prey individuals. Owls preyed upon 8 mammalian spp. [Sigmodon hispidus, Cryptotis parva, Reithrodontomys fulvescens, Baiomys taylori, Mus musculus, Peromyscus sp., Perognathus hispidus and Sylvilagus floridanus] and 2 bird spp. Hispid cotton rat (S. hispidus) was the most common prey species, and it contributed the greatest portion of consumed biomass. An adult owl was estimated to consume a mean of 54.8 g/day of prey biomass during the study, 84.3 g/day during the nesting seasons, 51.8 g/day during the prenesting season and 17.0 g/day during the postnesting season. Biomass consumption of adults increased (P < 0.02) from the prehatching period to 30 days posthatching; then consumption declined (P < 0.01) as the young fledged. The owlets consumed 69.9 and 64.8% of the total estimated consumed biomass of the spring 1976 and spring 1977 nesting seasons, respectively. Owlet consumption reached a peak value of 52.8 g/day .apprx. 28 days posthatching.

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