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Grassland Birds in Oregon’s Willamette Valley

Camas and the endangered plant Bradshaw’s lomatium attract Oregon Vesper Sparrows to this woodier prairie habitat in the Willamette Valley. Photo: Ann Kreager, ODFW.

Grassland Birds Need Conservation

Grassland birds in the Willamette Valley are in trouble. With less than one percent of the area’s historical prairie habitats remaining, the species that depend on open, grassy areas to feed and raise their young are declining. At the time of Euro-American settlement, the Valley was a mosaic of wet and dry prairies, oak savannas, and forests. Native Americans, who used many of the prairie plants for food, set fires to grasslands to enhance the growth of their favorite plants and create open areas for hunting and traveling. Fire prevented many shrubs and trees from growing, resulting in vast grasslands and wildflower meadows. Since that time, development and land use, cultivation, and restrictive and alternative burning practices have all altered the landscape.

Although it is impossible to recover the prairies lost to development and cultivation, many grassland birds can live alongside people if the existing habitat (e.g., grasslands, fallow fields, pastureland) is suitable. Alternative management techniques such as mowing and grazing can be used to mimic historical disturbance regimes. Ungrazed pastures dotted with shrubs can provide great year-round habitat. Lightly grazed or mowed pastures are also good habitat if mowing and grazing are rotated and timed to allow young birds to fledge and for flowers to seed. These surrogate grasslands can provide diverse plant structure and variability sufficient to allow for a place for birds to nest and feed. Wildlife and conservation reserves such as the Baskett Slough National Wildlife Refuge north of Dallas or the William L. Finley National Wildlife Refuge near Corvallis provide excellent examples of good habitat for grassland birds. By maintaining and restoring habitat for grassland birds, landowners will help not only them but many other plant and wildlife species as well, including the western pond turtle, Fender’s blue butterfly, Kincaid’s lupine, and California Quail. Habitat restoration also contributes to watershed health by reducing soil erosion and increasing water retention.

Threats to Grassland Birds

• Habitat loss: lack of habitat, small fragmented remnants, lack of connectivity, degraded grasslands with little/no management.
• Grassland management practices such as mowing, haying, grazing, and herbicide/insecticide application during the nesting season can be detrimental to grassland birds.
• Grassland nesting species are highly sensitive to disturbance during their primary nesting season (approximately April 1 to July 15). Late-nesters or birds that make a second nesting attempt may still be using grasslands into August. People, pets, feral cats, and management activities can cause birds to abandon their nests.

Strategy Species

The Oregon Conservation Strategy, Oregon’s official State Wildlife Action Plan, identifies a number of grassland birds that are in need of conservation. Grassland species of greatest concern include the following:

Western Meadowlark. 

Photo: Kathy Munsel, ODFW.

The Western Meadowlark is brownish in color with a bright golden-yellow breast and a black V-shaped patch across its breast. Meadowlarks are most famous for their bubbly, flute-like song. Males, who sing from perches to attract mates and advertise territories during the breeding season from April to mid-July, are polygynous and can have two to three mates at a time. A female lays four to five eggs, one per day; they hatch in 13 to 15 days. Like most young grasslands birds, they remain in the nest for 10 to 12 days after hatching. Unable to fly immediately after fledging, they remain under parental care for up to another two weeks. After the young fledge, the pair may re-nest and raise a second brood. Meadowlarks eat various insects, including beetles, crickets, grasshoppers, caterpillars, craneflies, sow bugs, and spiders. Territories average around 20 acres per family during the breeding season, but meadowlarks typically require large, contiguous grassland landscapes greater than 100 acres to establish viable populations. Meadowlarks prefer grasses and forbs of intermediate density and variable height (greater than 90 percent cover and 12 to 24 inches in height). Patches of bare ground are another component of preferred habitat. Because meadowlarks require large plots of land for breeding, land-use practices that result in small, isolated fragments of habitat lead to fewer or no birds.

Grasshopper Sparrow.

Photo: Aron Flanders, USFWS.

Named for their insect-like song, Grasshopper Sparrows are squat, short-tailed birds that hop and run on the ground, occasionally flitting to the top of a grass stalk or fence post to sing before retreating again to the grasses. These inconspicuous birds are spottily distributed in the central and south Willamette Valley, generally limited to lightly grazed pastures with few shrubs. Grasshopper Sparrows are very sensitive to the presence of large trees and tall woody vegetation in grasslands. Although this semi-colonial bird has a nesting territory of only three to five acres, it is associated with larger patches of grassland habitat just as meadowlarks are. Preferring grasslands of intermediate height (12 to 18 inches) with some bare ground, nests are built by females in a shallow depression. Females incubate four to five eggs for 12 to 13 days and may raise two broods if the conditions are right.

Oregon Vesper Sparrow.

Photo: Simon Wray, ODFW.

The sweet, tinkling song of the Oregon Vesper Sparrow can often be heard long after most other birds have ended the day, hence the name “vesper”. This large, pale, streaked sparrow feeds on insects, grass, and forb seed; nestlings primarily eat insects. Nests are shallow depressions on bare ground. The female generally incubates four eggs for 12 to 13 days and may have two broods per season. This migratory bird prefers grasses between 6 and 12 inches in height interspersed by small woody vegetation and bare ground. They can be found in edge habitat between grassy and wooded areas (e.g., fencerows, transition areas, young Christmas tree farms). Although the nests and eggs of the Grasshopper and Vesper Sparrow are similar, the amount of land they need to successfully raise their young is very different. The Vesper Sparrow may be present in smaller patches of habitat (10 to 20 acres) and is less tied to large landscape patches. Studies conducted in the Willamette Valley in 1996 and 2008 showed the Vesper Sparrow had the lowest measures of abundance and distribution of the Strategy grassland birds studied. Subsequent research has been underway since 2013 to improve understanding of rangewide abundance, distribution, and habitat relationships. The species was petitioned for listing as Endangered or Threatened under the federal Endangered Species Act in fall 2017, and petition findings are pending by the U.S. Fish and Wildlife Service.

Streaked Horned Lark.

Photo: David Maloney, USFWS.

The federally-listed Streaked Horned Lark, a striking bird with tinkling notes and black “horns”, prefers short, sparsely vegetated prairies and agricultural fields and even gravelly roadsides with short vegetation. Unfortunately, because they nest in vulnerable locations, their nests are often accidentally destroyed by farm machinery, ATVs, and traffic. Nomadic in the fall and winter, Streaked Horned Larks form territories when breeding. Larks typically lay four or five eggs which are incubated 11 days; young are able to fly 9 to 12 days after they hatch. Like meadowlarks and Grasshopper Sparrows, the species prefers large patches of contiguous grassland habitat in the landscape.

 

Short-eared Owl.

Photo: Keith Kohl, ODFW.

This owl, which prefers open country, weedy fields, wet meadows, and grasslands, is one of the rarest breeding grassland birds in the Willamette Valley today. It is one of the few that is crepuscular, that is, active at dusk and dawn. Not typically vocal, it is often detected by its slow, moth-like flight patterns and rare but conspicuous “bark.” Nests are shallow hollows on the ground often next to low shrubs or grasses. Short-eared Owl eggs have been found as early as March, with breeding extending through July and into August. The young are incubated up to 28 days but do not leave the nest for another 12 to 17 days; they are capable of flying about 10 days later. Breeding territories range from 50 to 200 acres. Favoring a small-mammal diet, this bird is a voracious hunter of rodents.

Common Nighthawk.

Photo: Nick Myatt, ODFW.

This nighthawk is most active at dusk, where it may be observed hawking insects on the wing. Common Nighthawks do not build nests. They lay their eggs on gravel bars, mudflats, or sparsely vegetated areas close to or within grasslands, making them very susceptible to disturbance. Its cryptic plumage helps conceal the female who lays two eggs which she incubates for 18 to 20 days, keeping her back to the sun all day long to regulate egg temperatures. Common Nighthawks have territory sizes ranging from 25 to 75 acres, but appear to key in to large, contiguous open patches of habitat. Common Nighthawks are often identified by their “peent” call while flying high in the sky from dusk to dawn. They prefer areas near riparian areas, open water, and forest clearings for foraging where insects concentrate. These birds winter in South America and migrate to Oregon to breed.

For More Information

• Check out the Oregon Conservation Strategy to learn more about Oregon’s grasslands and the Strategy Species that depend on them.

• If you are a landowner, view these resources for specific actions you can take to help enhance habitat and protect grassland birds on your property:
The Willamette Valley Landowner’s Guide to Creating Habitat for Grassland Birds
Managing Agricultural Land to Benefit Streaked Horned Larks: A Guide for Landowners and Land Managers
Restoring Native Habitats in the Willamette Valley

This article is based heavily on content originally developed by multiple organizations and individuals for The Willamette Valley Landowner’s Guide to Creating Habitat for Grassland Birds. Funding for the guide was provided by the Oregon Zoo Foundation’s Future for Wildlife Conservation Fund and the U.S. Fish and Wildlife Service’s State Wildlife Grant Program.