New World Warblers
Geothlypis tolmiei
The MacGillivray's Warbler is a small, furtive songbird often found in dense western brush. Though sometimes difficult to spot, its hurried song and sharp call note readily reveal its presence. This elegant warbler is characterized by its yellow and gray plumage amidst green foliage.
Typical adult measurements.
Individuals and populations vary.
01 / The telltale details
Start with shape and behavior. Then look for the smaller details.
Olive-green upperparts, bright yellow underparts, and a dark gray hood extending to the chest. Blackish lores and distinct white crescents above and below the eye are key features.
Similar to males but generally duller in coloration, with a paler gray hood and lacking the black lores.
Mostly olive-brown above with whitish eye arcs. The hood is grayish or brownish and often broken up by a pale throat, making them even more drab than females.
All plumages feature sharp white crescents (arcs) both above and below the eye, a crucial distinguishing mark.
02 / A place in the world
MacGillivray's Warblers breed in dense shrubby areas, such as willow and alder thickets near streams, or at the edges of coniferous or mixed forests. They favor new growth in logged or burned areas and brushy thickets in moist, low-lying ground or mountain canyons. During winter, they inhabit forest undergrowth in tropical foothills and mountains.
This species breeds across western North America, from southeastern Alaska and western Canada south through the Rocky Mountains and Pacific Northwest to southern California and Arizona. Its wintering grounds extend from central and southern Mexico to Panama.
MacGillivray's Warblers are long-distance migrants. They arrive on breeding grounds in mid-May and depart for wintering areas from late August through early September. During migration, they can be found in various shrublands and forests.
03 / Listen a little closer
The song is a hurried, varied series of whistles, often described as a "chip" call. Males sing loudly in the early morning during spring and summer.
04 / The life behind the feathers
Their diet consists primarily of insects and other arthropods, including true bugs, leafhoppers, beetles, bees, wasps, ants, and caterpillars. Occasionally, they may consume berries during migration and late summer. There is also a report of them drinking sap from sapsucker wells.
These warblers forage low in dense vegetation, typically less than 1 meter (3 feet) off the ground, though sometimes up to 2 meters (6 feet). They glean insects from foliage and branches, and also probe ground litter.
The female builds a cup-shaped nest of grasses, leaves, bark, and weed stems, lined with finer materials, typically 0.6 to 1.5 meters (2-5 feet) above ground in a shrub. Clutches usually contain 4 eggs, though they can range from 1-5. The female incubates the eggs for 11-14 days, and both parents feed the young, which fledge in 8-10 days.
MacGillivray's Warblers are generally shy and elusive, often remaining hidden within dense cover. Males sing to establish and defend territories, sometimes from conspicuous perches. Both sexes defend the area around the nest.
One more reason to pay attention
MacGillivray's Warbler was named by John James Audubon to honor Scottish naturalist William MacGillivray, despite John Kirk Townsend having previously named it "Tolmie's Warbler" after surgeon William Fraser Tolmie.
The ranges of MacGillivray's Warbler and the closely related Mourning Warbler overlap in parts of British Columbia, where they sometimes hybridize.
This species can nest at a wide range of elevations, from near sea level up to 3,000 meters (10,000 feet).
05 / An eye for the difference
MacGillivray's Warbler has distinct white crescents above and below the eye, which the Mourning Warbler lacks.
Male Common Yellowthroats have a distinct black face mask and an olive head, while females have a yellow throat.
The MacGillivray's Warbler has partial eye-rings, unlike the Connecticut Warbler which has a full eye-ring.
AI-assisted species research. Prepared September 2026. Details can vary across regions and populations.