Energetics of small body size and high latitude the Rufous Hummingbird in coastal Alaska

The Rufous Hummingbird is the smallest bird breeding at latitudes of 58° to 60°. Nesting chronology and food sequence was observed. The microclimate of the nest-site and its potential for heat loss during incubation were similar to those of hummingbirds in the Rocky Mountains at 39°N. Hummingbirds of lower latitudes increase their active-daylength in direct proportion to solar daylength (active day = 1.03 × solar day), whereas the Rufous Hummingbird tended to utilize less of the long daylength of coastal Alaska (active day = 197 min + 0.83 × solar day).