Colibríes de México y Norteamérica Hummingbirds of Mexico and North America

Abstract

We examined the distribution and abundance of hummingbirds at two study sites in southeastern Arizona, where we banded over 8000 individuals and 11 species in a 6-year period. We trapped approximately once a week from April to October at each site, from 1988–1992 at Sonoita, in oak woodlands, and 1991–1993 at Harshaw Creek, in a riparian area. Anna’s (Calypte anna), Black-chinned (Archilochus alexandri), and Rufous (Selasphorus rufus) Hummingbirds were the most abundant species. At Harshaw Creek, Broad-billed (Cynanthus latirostris) and Costa’s (Calypte costae) Hummingbirds occurred in significant numbers. A massive fall migration occurred at both sites, but few humming- birds moved northward in spring. The large numbers of migrants were spaced over time within seasons, and the timing of peak migration for a species varied among years. Fall- migrant Black-chinned Hummingbirds peaked earliest with adult males preceding adult fe- males and juveniles, followed by Rufous Hummingbirds (predominantly juveniles), then Anna’s Hummingbirds. Of the most abundant species, Rufous Hummingbirds used the sites only during their migration, and the other four species bred at one or both sites. During the first three years of feeder use at Harshaw Creek, Anna’s Hummingbirds significantly in- creased in numbers but other species did not. We also report how the age and sex classes for the common species varied in abundance between sites and among years.