Site-fidelity, longevity, and population dynamics of broad-tailed hummingbirds: a ten year study.

Abstract

In the course of other studies we have amassed a decade of records from banding, and observing the nests of, a breeding population of broad-tailed hummingbirds in Colorado, USA. In addition we have less extensive banding records for two other hummingbird species that migrate through the area but do not breed there. The rate of return of broad-tails between consecutive breeding seasons has been as high as 70% for females and 27% for males, suggesting substantial site fidelity and malebiased dispersal or mortality; our records also suggest that rufous hummingbirds are faithful to a particular migratory route. The oldest recaptured birds were at least eight years old, an age that exceeds predictions based on allometric extrapolation from other bird species; the apparent yearly survival rate of females is also unexpectedly high for birds of such small body mass. The earliest broad-tails to arrive at the start of the breeding season appear to be older, experienced individuals. Reuse of a specific nest site between consecutive years by the same female or different females seems to depend on the success of nesting efforts at that site. We have calculated the rate of change in size of the broad-tail population based on our estimates of female survivorship and fledging success. By this method the population appears to be declining, although nest counts themselves suggest that numbers of breeding females have remained fairly constant at least over the last seven years of our study.