Breeding ecology of the Barn Owl (Tyto alba) in Valencia (SE Spain)

We studied the reproductive parameters of a population of Barn Owls (Tyto alba) in Valencia (SE Spain) from 1989 to 1995. About one third of females laid second clutches, but the laying date of first clutches was not different for females laying one or more than one clutch per year. Also, there were no differences in the laying date of first clutches between years. Clutch size did not vary through the season, nor between the different study years. The main prey brought to the nests was rats, which represented the 62.6% of prey biomass. The modal clutch size was 5 eggs, and larger clutches were infrequent. This clutch size also produced more fledglings per nest than smaller or larger clutch sizes. This coincidence of modal and most productive clutch size is hypothesized to be related to the stability of climate and resource supply in the study area.