Dispersal behavior and survival of juvenile Tawny Owls (Strix aluco) during the low point in a vole cycle

Abstract

In 1996 we investigated dispersal and survival of juvenile Tawny Owls (Strix aluco) by radio-tracking in Kielder Forest, Northumberland, a man-made conifer forest in northern England. Here, Tawny Owls fed largely on field voles (Microtus agrestis) which exhibited a 3-4 year cycle of abundance, with some spatial asynchrony. Generally, vole numbers were at the low point of the cycle in 1996. Twenty-two nestlings from 11 two-chick broods were radio-tagged when 22-31 (mean 26.3) days old. Birds fledged when 29-36 (mean 32.1) days old. Eight (36.4 percent) owls died 10-106 days after fledging and before dispersing from their natal territories. Five (22.7 percent) owls died outside their natal territories 40-147 days after fledging. Five (22.7 percent) owls disappeared suddenly at 8-51 days after fledging and before the end of the dependence period, and evidence suggested that they were predated. Contact was lost with four (18.2 percent) birds 58-178 days after fledging and after they had begun to disperse. Radio-tracking data are discussed in relation to movement patterns, food resources, and habitat preferences of juvenile owls in the post fledging period.

Parent Publication

• Biology and conservation of owls of the Northern Hemisphere: 2nd International symposium

Citation

Coles, C.F.; Petty, S.J. 1997. Dispersal behavior and survival of juvenile Tawny Owls (Strix aluco) during the low point in a vole cycle. In: Duncan, James R.; Johnson, David H.; Nicholls, Thomas H., eds. Biology and conservation of owls of the Northern Hemisphere: 2nd International symposium. Gen. Tech. Rep. NC-190. St. Paul, MN: U.S. Dept. of Agriculture, Forest Service, North Central Forest Experiment Station. 111-118.