How to Find Out if Birds Are Mating

Listen for bird calls. Some of the primary motivations for birdsong are the attraction of mates and the defense of territories, both related to breeding. In many bird species, the female selects a desirable male to initiate mating. Often, as with the red-winged blackbird, the appeal seems to be males with the best territories. "Female Red-winged Blackbirds consistently choose high-quality territories rather than particular males," writes Frank B. Gill in Ornithology (1995); a high-quality territory means one blessed with good cover, plentiful food and other factors. Across much of North America, the melodic, rasping call of the male red-winged blackbird over freshwater marshes reveals their territorial season, the mating summons and the onset of spring.

Look at plumage. Binoculars are helpful. Some birds develop special plumage during the breeding season, molting from drabber hues to flashier ones for the purpose of advertisement. Adult black-bellied plovers, for example, fulfill the plumage pattern of their name only during the breeding season and are otherwise pale and less distinctive.

Watch for breeding behavior. This can include striking physical displays. The male woodcock of eastern North America, for example, makes acrobatic twilight flights over field and prairie during the spring mating season, the air passing over his outer tail feathers making a distinctive whistle. It might involve food: Male common terns present their mates with fresh-caught fish during courtship and into the nesting period.

Consider the season. Birds tend to mate soon before or during the period of richest food availability, so that they might raise their broods in the most productive environment. In North America, this is generally spring and early summer.