MacGillivray's Warbler

MacGillivray's Warbler closely parallels the Mourning Warbler in appearance and habits but occupies the western half of the continent. Males show a gray hood over the head and upper breast, with blackish lores in front of the eye, while the rest of the underparts are bright yellow and the back is plain olive-green.

Its most useful field mark is a pair of bold, broken white crescents forming incomplete "spectacles" above and below the eye, a pattern the closely related Mourning Warbler lacks or shows only faintly. Females and immatures are duller, with a paler grayish hood.

Key field marks

• Gray hood over the head and breast, with blackish lores in males
• Bold, broken white eye-crescents ("spectacles") above and below the eye
• Olive-green back, bright yellow underparts
• No wingbars

Similar species

Mourning Warbler is nearly identical in overall pattern but lacks the bold white eye-crescents, showing at most a faint, thin broken eyering; the two species' breeding ranges are largely separate (MacGillivray's in the West, Mourning in the East), with only limited overlap.

MacGillivray's Warblers breed in dense shrubby understory across the mountains of the western United States and western Canada, including montane thickets, regenerating burn areas, streamside willow and alder tangles, and shrubby forest edges at a range of elevations.

They winter from Mexico south through Central America, favoring similarly dense, shrubby habitat.

Behavior and voice

Like its eastern counterpart, MacGillivray's Warbler is a skulking species that stays low and hidden in dense vegetation while foraging for insects and spiders, making it easier to hear than see.

The song is similar to that of Mourning Warbler, a husky, rolling series often rendered as "sweeter-sweeter-sweeter-sweet."

Nesting

The nest is built low in dense shrubs, often just above the ground, made of grass, bark strips, and leaves. Clutches typically contain 3-5 eggs.