Postfledging Survival and Recruitment of Known-Origin Roseate Terns (Sterna dougallii) at Falkner Island, Connecticut

Abstract

-From 1981-1990, 166 (10.1%) of 1636 Roseate Tern (Sterna dougallii) chicks banded from 1978-1985 at Falkner Island, Connecticut, and 68 (1.0%) of 6904 chicks banded during the same time period at all other colony sites in Connecticut, New York, and Massachusetts, were recaptured as breeding adults at Falkner Island. An analysis of the recapture data of the natal-site recruits resulted in an estimated average survival-and-return rate of 14.7% for the 3-yr period from fledging to first breeding. Assuming a 10% permanent emigration rate of surviving young to other colony sites, the overall prebreeding survival or maturation rate to age 3 of all fledglings raised at Falkner Island from 1978-1985 was estimated to be about 16%. The 1636 chicks banded at Falkner Island comprised only 19.7% of the total of 8540 chicks banded in the three-state area, but the 166 adults that returned to their natal colony site accounted for 71.4% of the 234 known-age survivors from the 1978-1985 cohorts that had nested at Falkner Island through 1990. The recapture as adults of birds first banded as chicks provides an estimate of the maximum degree to which the breeding population at this site was sustained by natal-site recruitment. The capture of a large number of unbanded birds and birds banded as adults elsewhere indicates, however, that about two-thirds of the recent additions to the Roseate Tern breeding population at Falkner Island were immigrants recruited from other colony sites. Received 24 April 1990, accepted 22 April 1991.