MacGillivray’s Warbler

Identification

MacGillivray's warbler is a small songbird, measuring 10 to 15 cm long with a wingspan of 19 cm and weighing just 9 to 13 grams. Adult males are distinctive, featuring a medium gray head and nape with darker gray to blackish lores and eye-line, contrasted by bold white crescents above and below the eye. The back is yellowish olive-green, while the throat and upper breast are medium gray. The lower breast displays characteristic black mottling, and the remaining underparts are yellow with an olive-green wash on the flanks. Adult females are noticeably paler, with a more glaucous crown, less prominent eye markings, and pale gray throat and breast without the male's bold mottling. Both sexes share a black iris, dusky brown upper mandible, and pale pinkish buff lower mandible.

Range & Habitat

MacGillivray's warbler is found from southeastern Alaska and western Canada south to Panama, with two recognized subspecies occupying different regions. The nominate subspecies breeds west of the Cascade Range and Sierra Nevada from southeastern Alaska to about the latitude of Los Angeles, while the monticola subspecies occupies areas east of these mountain ranges from eastern British Columbia south through the Rocky Mountains to southern Utah and Colorado. The species winters mostly in Mexico and Central America, with the nominate subspecies in southwestern Mexico through western Panama, and the monticola subspecies in central to southern Mexico.

During breeding season, MacGillivray's warbler favors forest types with dense undergrowth and moderately open canopy, frequently inhabiting regenerating clearcuts and burned areas. In the southern parts of its range, it often uses riparian zones. During migration and winter, it occurs in shrublands, forests, and shade coffee plantations, preferring lower-elevation mangroves and forest edges in winter, and higher-elevation forest undergrowth.

Behaviour & Diet

MacGillivray's warblers are insectivorous, feeding on a wide variety of larval and adult insects gleaned from leaves and branches, particularly from low vegetation and ground level. Males are vocal singers, producing a distinctive primary song of 6-8 syllables described as "churry churry churry churry cheery cheery," typically sung at dawn and dusk from high perches. Both sexes make harsh chip notes and high-frequency calls. The species migrates on a fairly broad front, with fall migration spanning from late July to late November and spring migration from mid-March to mid-June.

Best Time & Places to See It

Birders and nature travelers can encounter MacGillivray's warbler during breeding season from late April through mid-August in the western mountains and regenerating forest areas of North America. Spring migration (mid-March to mid-June) and fall migration (late July to late November) offer additional viewing opportunities, when birds move through a variety of habitats including shrublands and non-forested areas. Winter sightings are possible in Mexico and Central America, particularly in forested areas and shade coffee plantations. The species' preference for dense undergrowth and low perches makes it challenging to observe compared to canopy-dwelling warblers, but dawn and dusk singers are most vocal and therefore most detectable.

Photography Tips

Photographing MacGillivray's warbler requires patience and attention to the bird's behavioral patterns. Position yourself near dense undergrowth and shrubby habitats where the species feeds and nests, typically within a meter of the ground. Early morning and late evening offer the best opportunities, as males sing most actively during these times from higher perches where they may be more visible and photographable. The bird's small size and preference for shadowy, vegetated areas demand a fast shutter speed and potentially higher ISO settings. Focus on capturing the distinctive facial pattern—the bold white eye crescents and dark lores are key field marks. During migration, scan brush and riparian areas where the species pauses to feed, as birds may be more exposed and active in these transitional habitats.