Old World Warblers: Sylviidae

Many members of this bird family mate for a single nesting or a season, with some mating for life. Males of some species keep two or more females, maintaining separate nests and young. Serial monogamy (muh-NAH-guh-mee), or mating for a single nesting then finding another mate or mates for other nestings, is quite common. Some males have as many as eleven nestings in a season.

Courtship behavior is equally diverse among Old World warblers. Some males will sing elaborate songs. Others will dance, displaying a variety of postures. Still others build nests for show and bring objects as gifts to females.

Old World warblers create nearly every shape and type of nest imaginable. There are cup-shaped nests, domed nests, and round balls that are built from all kinds of plant materials, including moss, lichen, twigs, and grasses. Some nests are built on the ground, some in bushes, and others in trees as high as 80 feet (26 meters). Nests are wedged into the forks of branches or tucked into crevices in walls. Some are hung from vines or leaves. Tailorbirds actually sew their nests. The female punctures leaves with her bill and threads grasses through the holes, even knotting the ends so the nests don't unravel. Both sexes of some species build nests. Females alone will build nests among species whose males have more than one mate.

Females lay one to twelve eggs and incubate them, or sit on them until they are hatched, alone. Males of a few species share this duty. The eggs remain in the nest for ten to twenty-one days and are fed by their parents for one to four more weeks. The young have no feathers at birth.

Some Old World warblers forage with many different species in large groups. Others will only feed with their own family group or with their mates.

Some species spy insects from a perch and swoop down on them. Other species stand on the ground and scoop up insects. A few species will either scratch through the litter on the forest floor or use their wings to move the leaves about. Kemp's longbill will poke its bill into dead wood found on the ground.

Old World warblers are a vocally diverse family. Nearly all of them have developed song patterns that range from strictly unmusical repetitions to beautiful, complex melodies. Songs are used to mark territory, attract mates, and communicate with family groups. Duets are songs between bonded mates.