American Redstart

The American Redstart differs from most other warblers in its propensity for flycatching, although it also spends significant time picking insects from leaves like its relatives. To facilitate the capture of aerial prey, redstarts have a wider bill and longer rictal bristles (modified feathers that surround the beak) like a small flycatcher. It’s also suspected that the bright patches of orange (in males) or yellow (in females) on redstart tails serve to startle insects as the birds actively fan their tails while they move through the foliage.

Male redstarts take two years to obtain their bold black and orange plumage, with one-year-old birds looking much like females. If you see what looks like a female singing, look extra closely and you might see a few black feathers around the face or breast that indicate it is actually a young male. Why male redstarts exhibit such “delayed plumage maturation” is unclear, but it might have something to do with minimizing direct competition with more mature birds. Indeed, studies of redstarts in New Hampshire suggest that yearling males are less likely to attract a mate than older ones and are often relegated to less suitable habitats such as older forests or those with more coniferous trees.

This phenomenon of “extra” males would imply that females are less common, and studies of redstarts on their Caribbean wintering grounds provide a possible explanation. Outside the breeding season, males and females defend exclusive territories, and males are socially dominant. Females are thus forced into poorer (often drier) habitats and may be likely to survive if conditions deteriorate. This discrepancy between male and female survival has likely been exacerbated by human alteration of habitats on the winter grounds. If there was more good habitat females would not be as likely to be excluded by males. Declines in redstart populations are likely the result of factors operating in winter as described here, and in summer through maturation of young forest habitats and possibly changes in predator populations.