Another highly irruptive finch, large numbers of Evening Grosbeaks can invade neighborhoods one year and be completely absent the next. In Spring, Evening Grosbeaks move through the Willamette Valley and Portland area, often concentrating in places with Big-leaf Maple, Oregon White Oak, or in towns with large elm trees. Watch for peak numbers to continue through May. By mid-June they will have moved into the mountains, where they prefer coniferous forest for breeding. Evening Grosbeaks are sometimes seen at feeders in fall and winter in our area, but usually in smaller flocks than in the spring.
Black-throated Gray Warbler
The first wave of Black-throated Gray Warblers have arrived, and many of the males are already on territory. Female Black-throated Gray Warblers leave their wintering grounds about two weeks later than the males, so the next wave, arriving late April to early May, will be mostly females. Black-throated Gray Warblers can be found in a variety of habitats depending on where you are in the state. In the Portland area and mountains they are found in riparian corridors, coniferous forest, and oak woodland. In Eastern Oregon, they prefer juniper trees and stands of Mountain Mahogany. Birds that breed west of the Cascade arrive from West Mexico (south Sonora to Oaxaca).
The old name for Wilson’s Warbler is the more descriptive Black-capped Flycatching-Warbler. Wilson’s Warblers are easy to see as they often search for insects near eye-level and make short sallies to catch their prey. Watch for visiting Wilson’s Warblers in the shrub layer as peak numbers arrive through mid-May. Pacific breeders arrive from a vast wintering area, where they favor mountainous habitat from Sonora all the way down to western Panama. Once on breeding territory, Wilson’s Warblers prefer the dense understory of mature coniferous forest. Some of the highest population densities of breeding Wilson’s Warblers occur in the coastal mountains of the Pacific Northwest.
Hammond’s Flycatchers are the first flycatcher from the genus Empidonax to arrive in our area, with the first few seen in mid-April. Good numbers will pass through the first week of May and could be seen in neighborhoods and gardens. Breeds in mature and old-growth coniferous forest where it spends time in the mid to high canopy. Migrants arrive from the mountains of south-central Mexico to Honduras. Watch for the upright posture and the return to the same spot after sallies for insects. Migrants overlap with similar flycatcher species, but only Pacific-slope and Dusky (not common) early in the season.
The earliest Cassin’s Vireo may have arrived a few weeks ago, but the main movement will be occurring throughout the first week of May. In the spring, Cassin’s Vireos arrive from south-central Mexico and then take a more coastal route north. They breed in a variety of habitats, from White Oak woodland to mixed coniferous forest in the low to mid-elevations. After the breeding season, they move to higher elevations to molt all their feathers over a six week period. Then they probably take a more mountainous route south. Listen for the song of these spectacled canopy dwellers, which is a series of short repeated phrases, that sounds like questioning and answering. There is evidence that at least some birds have a second breeding season in northwestern Mexico, during the “second spring” of the monsoon season in July and August, though it is unclear where these vireos are arriving from.