SCIENTIFIC NAME: Cardellina pusilla
The Wilson's Warbler is a small bright olive and yellow warbler, lacking wing bars, tail pattern or streaking. It has a round body and a large head.
Both sexes measure about 3.9 - 4.7 inches in length, with a wingspan of 5.5 - 6.7 inches and weight of 5 - 10 grams.
Males have a neat black “skullcap”.
Females show little or no black on crown.
They have a thin pointed and blackish bill, with upper mandible darker than lower, yellow supercilium and underparts, and olive upperparts. Legs are pale brown. Tail is relatively long and thin. Black eyes stand out on the plain face.
CALL: Usual call is a sharp “chip”.
SONG: A rapid, staccato, chattering “chi-chi-chi-chi-chi-chet-chet”, dropping in pitch at end.
Eastern birds tend to sing a descending song, while western birds sing on one pitch, increasing in volume.
Feeds mainly on insects, bees, beetles and caterpillars, and spiders. Occasionally they will eat some berries.
Breeds in waterside thickets, especially willows, alders or dwarf birches, streamside tangles and, in mountains, bushy hillsides or alpine meadows.
In migration, they can be found in a variety of shrubby habitats, including suburban hedges and gardens.
Breeding range extends north to the limit of trees from Alaska to Newfoundland and Nova Scotia, and in the West, south to northern Arizona and southern California.
It winters from Louisiana southward to Panama.
The female builds a relatively large and bulky nest with dead leaves, rootlets and moss, shredded barks and grass, and lined with soft plant material and hair.
She lays 4 - 6 white to creamy eggs with fine reddish-brown speckling or spotting. She incubates them for about 11 - 12 days.