Annual adult survival in several new world passerine birds based on age ratios in museum collections

Abstract

We estimated annual survival from proportions of first-year and older birds in museum collections of several species of North American and Neotropical passerine birds (Order Passeriformes). The quality of estimates of survival from museum specimens depends on accurate aging, usually based on plumage markers, and unbiased collecting. The advantages of an age-ratio approach are broad temporal and geographic sampling, large sample sizes, reduced bias from adult dispersal, and access to species and areas not readily sampled in mark–recapture studies. Biases in estimated survival due to sex- and age-based biases in collecting are discussed in detail. Survival estimates were higher in tropical compared to temperate populations/species in Pyrocephalus, Icterus, Pheucticus, and Cyanocompsa, but not Catharus. In seven of nine North American species, estimates of survival from museum collections exceeded those obtained in local MAPS mark–recapture studies. Generalizations concerning adult survival rates in natural populations continue to be elusive, but the use of a variety of estimation approaches will enrich the empirical database and strengthen confidence in perceived patterns of life-history traits.