cerulean warbler

cerulean warbler (Setophaga cerulea) [female] [state threatened]
Photo © Rob Curtis/The Early Birder

cerulean warbler (Setophaga cerulea) [male] [state threatened]
Photo © Mary Kay Rubey

FEATURES
The cerulean warbler averages four and one-half inches in length. The male has blue feathers on the back and white feathers underneath. He has a thin, black band that can be seen on the upper chest. The female has olive-green feathers on the back and white feathers underneath. She has a white line on the head directly above each eye. Both sexes have two, white bars on each wing.

BEHAVIORS
The cerulean warbler is a migrant and summer resident statewide. It winters as far south as northern South America. Spring migrants begin arriving in Illinois in April. The nest is built in a large tree at a height of 20 to 60 feet above ground. It is composed of grasses, plant fibers, bark, mosses and lichens and lined with plant fibers, mosses and hair. Spider webs are collected and used to help hold the nest together on the outside. The female lays three to five white, gray-white or green-white eggs that are speckled with brown, and she alone incubates them. Fall migration begins in August. This bird lives in the treetops in bottomland forests and upland forests. Its song is a “buzzing” sound like “zray zray zray zreeeee.” Like all warblers, this bird feeds on insects.

​Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Passeriformes
Family: Parulidae

The cerulean warbler prefers to live in forests of more than 1,000 acres in size and is rarely found in forests smaller than 200 acres. This species was once abundant in the state, but loss of large tracts of forested habitat has been detrimental to it.