INDICATORS OF MALE QUALITY IN THE HOOTS OF TAWNY OWLS (STRIX-ALUCO)

The number of songs in a male's repertoire, and the amount of time he spends singing, have been shown to correlate with territory size and q uality, reproductive success, parental care and parasite load in some passerine species. In addition, females of some species use song rate and complexity as a cue to mate choice and are more responsive to more frequent and complex songs. Few studies, however, have examined the i nfluence of body size and parasitic infections on the sound frequency (pitch) and structure of vocalizations of birds. The Tawny Owl (Strix aluco) hoot is important in communication between birds at night when visual information is limited, and is simple enough to allow a quantit ative analysis of its structure. Six temporal and four frequency measu res of the hoots of 50 Tawny Owls were taken, and compared to body mas s, wing length, breeding success and number and intensity of parasitic infections of the singers. There was a decrease in call frequency wit h increasing body mass and the vibrate tail of the last note was longe r in larger birds, but there was no part of the call that correlated w ith breeding success. There was an increase in call frequency as the n umber of parasitic infections increased, and there was a decrease in t he length of calls as the intensity of parasitic infections increased.