Wilson's Warbler

The Wilson's Warbler is a tiny, vividly colored warbler, bright lemon-yellow below and olive-green above, with a beady black eye that stands out against the plain yellow face. Adult males wear a small, neat black skullcap that gives the species its alternate name, while females and immatures show a duller, sometimes barely-there cap.

Restless and constantly in motion, Wilson's Warblers are famous for flicking their tails as they hop through low, dense vegetation, a habit that often helps observers pick them out even in thick cover.

Key field marks

• Bright yellow underparts and olive-green upperparts
• Round black cap on adult males (reduced or absent in females/immatures)
• Plain face with a dark beady eye and no eyering or eyeline
• No wingbars
• Frequent tail-flicking while foraging

Similar species

Female and immature Wilson's Warblers lacking a strong cap can resemble Yellow Warbler or Hooded Warbler females, but Wilson's is smaller, plainer-faced (no eye markings), and lacks the yellow tail spots and larger size of Hooded Warbler, while Yellow Warbler shows yellow tail spots and a heavier build.

Wilson's Warblers breed across a huge range from Alaska and much of Canada south through the western mountains to California and the Rockies, typically in dense shrubby thickets near streams, bogs, and wet meadows, including willow and alder tangles. A small, disjunct population also breeds in the northeastern United States.

They winter from Mexico south through Central America, with some reaching northern South America, generally favoring similar shrubby, humid habitats at low to middle elevations.

Behavior and voice

Active and low-foraging, Wilson's Warblers glean insects from leaves and frequently sally out to catch flying insects in mid-air, flicking their tails almost continuously. They forage lower in vegetation than many warblers, often within a few feet of the ground.

The song is a rapid, chattering series of "chi" notes that drops in pitch toward the end, often rendered as "chi-chi-chi-chi-chi-chet-chet."

Nesting

The nest is built by the female directly on or very near the ground, tucked into a mossy hummock, grass tussock, or shrub base, and consists of a bulky cup of moss, leaves, and grass. Clutches typically hold 4-6 eggs.