Minimum longevity and age-related male plumage in Darwin’s finches on Floreana Island

Abstract

Several Darwin’s finch populations on the Galapagos Islands are declining and/or locally extinct. Acoustic surveys provide useful information about population size, but do not provide information on the age or morphology of birds. This study uses mist netting data collected during 2004–2016 on Floreana Island with the aim of evaluating minimum longevity in Darwin’s finches. The study species are the Small Tree Finch (Camarhynchus parvulus), hybrid tree finches (Camarhynchus spp.), Medium Tree Finch (Camarhynchus pauper), and Small Ground Finch (Geospiza fuliginosa). In total, 1032 Darwin’s finches were mist netted and 86 of 707 males and 14 of 325 females were recaptured across years. We used the proportion of black plumage to age males, and the age at first capture plus the number of years between recapture to estimate minimum longevity. Minimum longevity ranged from 12 to 15 years and was lowest in the critically endangered C. pauper (12 years). The average number of years between first capture and last recapture was significantly lower in females than in males. Because long-term mist netting provides information on age structure, recruitment and longevity in males and females, it should be a key component of effective conservation planning.