Birds

of Tualatin River National Wildlife Refuge
Kingfisher - Douglas Beall - 512x289

Waterfowl

Providing high-quality habitat for waterfowl has been one of the priorities on the Refuge since its establishment. Waterfowl are primarily associated with wetlands; however, they also use upland grasslands and croplands.

Breeding at the Refuge

Typically, few numbers and species of waterfowl breed on the Refuge and surrounding areas. A limited number of western Canada geese, mallards, gadwalls, cinnamon teal, hooded mergansers, and wood ducks annually raise a few broods. Buffleheads, northern shovelers, and blue-winged teal are rare breeders here.

Migration

In early fall, waterfowl numbers remain low as migration begins; their numbers then increase sharply during November. Numbers remain relatively high to the end of January when waterfowl hunting season ends, and then birds tend to disperse to nearby private lands before migrating north near the end of March.

The Refuge lies in the Pacific Flyway, where birds migrate primarily from breeding grounds in Alaska, British Columbia, Alberta, the Yukon, and Northwest Territories, and to a lesser extent from Saskatchewan. For many of these birds, the Refuge is an important stopover to wintering areas in California and Mexico, and for others it is their southern terminus, where they spend the winter.

Surveys

Detailed weekly winter waterfowl surveys have been conducted on the Refuge since 2000, and the area surveyed has increased over time as land has been acquired and/or restored. Surveys are conducted from September through at least February each year. 

 

Songbirds

The Refuge supports a host of both resident and migratory songbirds that use all of the habitat types represented here. About 100 songbird species have been identified on the Refuge and many of those species breed here.

Point count surveys have been conducted to identify species using the Refuge, and a bird banding program has been established under the Monitoring Avian Production and Survival protocol to assess productivity and survival of locally breeding birds. These surveys will help to determine long-term trends in songbird populations on both a local and regional scale.

Shorebirds

There are relatively few shorebirds that use the Refuge, and species diversity is low. Twenty-one species have been recorded, but many of those are one-time or rare sightings.

Most Common Species

Killdeer, spotted sandpipers, and Wilson’s snipe are among the most numerous; all of them breed at the Refuge. Least and western sandpipers, dunlin, lesser yellowlegs, and long-billed dowitchers are also commonly sighted during migration.

Breeding, Migration, and Foraging

Although some shorebirds do breed here, the majority of shorebirds are migrants, passing through during spring and late summer and fall. Typically, mudflats in wetland margins are available for shorebird foraging from early spring through summer as managed wetlands are drawn down on their annual cycle.

Surveys

Regular weekly surveys are conducted from April through September on several of the Sherwood Units. Weekly counts average fewer than 50 individuals, but may number several hundred on rare occasions. 

 

Marsh Birds and Waders

Marsh birds use both herbaceous and scrub-shrub wetlands, and to a lesser extent adjacent uplands.

Breeding

Breeding has been verified on the Refuge for each of these species, although they occur in relatively low numbers. Early spring drawdown of wetlands to meet other management objectives may have a negative effect on these species. The first confirmed breeding of American bitterns on the Refuge was observed at a recent scrub-shrub wetland restoration site.

Surveys

Surveys for sora, Virginia rail, American bittern, American coot, and pied-billed grebe are conducted using recorded calls from April through June each year. Wading birds such as great blue herons, great egrets, and green herons are surveyed in conjunction with shorebird and waterfowl surveys. Great blue herons and great egrets are present nearly year-round on the Refuge, while green herons are usually only observed during summer.

Raptors

At least 18 species of raptors have been recorded on the Refuge including eagles, hawks, falcons, and owls. Bald eagles, red-tailed hawks, American kestrels, and great horned owls are year-round residents. Other species such as peregrine falcons are usually only present during winter when waterfowl populations are high. Some species are regular summertime visitors, such as ospreys that forage on fish as wetlands are drawn down.

Raptors are specialized in the habitat types that they use and may be observed in most habitat types on the Refuge. Eagles and peregrine falcons use wetlands for hunting waterfowl. Great horned owls hunt rodents in the forest at night while Cooper’s hawks hunt in the forest during daylight in search of songbirds. Northern harriers hunt in the uplands, croplands, and wetlands during the day, while barn owls hunt open fields during the night and evening.

The Refuge has installed American kestrel nesting boxes and will monitor these from time to time to determine nesting success. There are no other surveys that specifically target raptors, although raptors are recorded during songbird point count surveys. 

Facts About Birds