Post-release survival of hand-reared tawny owls (Strix aluco) based on radio-tracking and leg-band return data

摘要

The post-release survival of hand-reared tawny owls (Strix aluco) was measured using radio-tracking and leg-band return data. Of 16 birds fitted with 2.4 g radiotelemetry togs, two shed their togs after four and nine days, respectively and one bird was recovered and the tag removed. The remaining 13 birds were tracked for between 16 and 84 days (median 38). Of these, two were found dead (one emaciated and one predated) and one was recovered alive but emaciated and was subsequently euthanased. Thirty-seven percent were radio-tracked for more than six weeks, thought to be the critical period beyond which raptors will mostly survive. Of 112 birds banded between 1995 and 2005, 18 were recovered (seven live and 11 dead). Of the seven live recoveries, three were involved in road traffic collisions. Of the dead recoveries for which the cause of death was known (n = 4), all had been involved in road traffic collisions. The time elapsed between release and recovery ranged from 1-2,246 days (median 123 days). Over 65% survived for more than six weeks. The distance travelled between release and recovery ranged between 0 and 6 km (median 0). Further work is required on the effects of hand rearing on post-release survival of rehabilitated wildlife.