Date of Award
Master of Science
Wildlife and Fisheries Science
Ralph W. Dimmick
James T. Tanner, James L. Byford
The objectives of this study were to: (1) delineate the nesting cycle of the screech owl (Otus asio) in Tennessee, (2) investigate food habits of the screech owl in Tennessee and (3) determine the adaptability of the screech owl to artificial nesting structures in a variety of habitat types.
Based on 25 active screech owl nests examined in east Tennessee in 1978, average clutch size was 4.1. An incubation period of 25-26 days was determined from daily monitoring of two of these nests. Peak egg laying, hatching and fledging periods were 29 March-11 April (80%), 26 April-9 May (76%) and 24 May-6 June (82%), respectively, from 25 nests examined in 1978.
Sexual size dimorphism between male and female screech owls was slight. Of 74 screech owls collected dead on roads (DOR) in Tennessee, the culmen, tarsus, and tail lengths of female owls were not significantly larger than those of male owls. However, wing lengths of female owls were significantly larger than wing lengths of male owls.
Food habits information was obtained from identification of food items cached in nest boxes and from analysis of stomach contents of DOR birds. Food caches revealed a preponderance of birds consumed in all seasons; stomach contents indicated the importance of mammals in late fall and winter and insects in spring and summer.
From 117 DOR screech owls collected from November 1976 to June 1978 in Tennessee, 89 (76.1%) were red, 25 (21.3%) were gray and 3 (2.6%) were intermediate in coloration. Ratio of red to gray phase birds was 3.6:1.
Use of 150 nest boxes examined in 1977-1978 (50 each in rural, urban-suburban and woodland areas) by roosting screech owls was significantly higher (p < .05) in urban-suburban and rural areas than in woodland areas. Boxes in urban-suburban areas supported the largest number of nesting screech owls. In the woodland area, 40 nest boxes were never used by vertebrate animals; this was compared to four and five next boxes that were unused in rural and urban-suburban areas, respectively.
Duley, Linda J., "Life history aspects of the screech owl (Otus asio) in Tennessee. " Master's Thesis, University of Tennessee, 1979.