REPRODUCTIVE-PERFORMANCE, AGE STRUCTURE, AND NATAL DISPERSAL OF SWAINSONS-HAWKS IN THE BUTTE-VALLEY, CALIFORNIA

We monitored annual occupancy, reproductive performance, and natal dis persal of a marked population of Swainson's hawks (Buteo swainsoni) fr om 1984-94. Annual territory occupancy varied from 61-90%. Mean annual nest success was 65% (SE = 3.4%), and annual fledging rate was 1.53 ( SE = 0.14) young per nest attempt. Of 567 Swainson's hawks banded as n estlings during this study, 41 were later recaptured as breeding adult s. Mean age at recapture was 5.9 yr (SE = 0.37; range = 3-15 yr. The m ean age of color-marked adults observed in either 1933 or 1994 was 8.2 yr (SE = 0.52), and ranged from 4-15 yr. Dispersal distances from nat al site to subsequent breeding site ranged from 0-18.1 km (mean = 8.2 km, SD = 3.1), and was not different from random distances among terri tories.