Oregon vesper sparrow (Pooecetes gramineus affinis)

Physical description

Vesper sparrows are a large sparrow (6 inches in length) with pale brown-streaked plumage, white outer tail feathers, rufous lesser wing coverts, and a white eye-ring. The Oregon vesper sparrow subspecies has medium grayish-brown upperparts and white underparts with a buff tinge.  

Ecology and life history

Oregon vesper sparrows typically nest in dry, open landscapes, with moderately short and structurally diverse grass and forb cover with some patchy bare ground and sparsely vegetated areas. They generally avoid wet areas or sites with tall, dense herbaceous vegetation. Structural diversity of herbaceous vegetation appears to be an important factor in site selection.

A mix of bare ground and short vegetation is chosen for foraging, moderate structured vegetation for nesting, and scattered taller vegetation, including shrubs and scattered trees, is used for cover and singing perches. Fence posts, fences and other man-made structures are often used for singing perches. Prairie size also appears to be an important factor in site selection, with only large prairies currently occupied.

Adults take dust-baths in sandy forest roads, ruts in the road, and bare spots under vegetation, and seek out shade during mid-day. 

Vesper sparrows eat a wide variety of insects during the breeding season supplemented with seeds during migration and winter. They primarily forage while walking on the ground but will also hop and hover to feed. Adults provide nestlings with invertebrates and rarely seeds. 

Vesper sparrows build a bulky, loose, cup-like nest of grasses and rootlets on the ground in a small depression, often near the base of a grass clump, weed, or shrub. The female typically lays three to five eggs in mid-May and incubates them for 11 to 13 days. The young fledge in 7 to 12 days, and pairs commonly raise two broods per season. Vesper sparrows exhibit relatively high annual site fidelity to nesting areas and defend small territories during the breeding season.

Banding records have reported birds more than 6 years old.  

Vesper sparrows migrate in flocks of 30 or fewer.

Geographic range

Vesper sparrows occupy open habitats (grassland, shrub-steppe, and agriculture) across much of central and southern North America. The Oregon vesper sparrow is the rarest of four recognized subspecies. It has a restricted breeding range that includes southwestern British Columbia, western Washington, western Oregon, and northwestern California. It is migratory and overwinters rom central California west of the Sierra Nevada Mountains to northwestern Baja California, Mexico.  

Historical accounts suggest the Oregon vesper sparrow was locally uncommon to abundant in the disjunct distribution of grassland and savannah habitat in western Washington. It has experienced range-wide population declines and range contractions, and many local extirpations. In Washington, this includes 20th century extirpations from Vashon Island of the north Puget lowlands, and the Dungeness area of the Olympic Peninsula; and extirpation from San Juan Island appears likely. It is now mainly limited in Washington to remnant prairies and grasslands in Pierce and Thurston Counties, with smaller numbers on islands in the lower Columbia River and grasslands on San Juan Island; a few may still breed in eastern Clallam County and near Shelton (Mason County).  

Approximately 90% of the population occurs in the south Puget lowlands, predominantly on Joint Base Lewis-McChord. The current range-wide population estimate is less than 3,000 birds with approximately 300 of those occurring in Washington.

For maps of range-wide distribution and conservation status of this species, check out NatureServe Explorer and the International Union for Conservation of Nature Redlist.