(Map may reflect historical as well as recent sightings)
The streaked horned lark was added to the candidate list in October 2001. On October 3, 2013, the streaked horned lark was listed as a threatened species under the ESA.. More information.
The streaked horned lark is endemic to the Pacific Northwest, and is a subspecies of the wide-ranging horned lark. Horned larks are small, ground-dwelling birds, approximately 16−20 centimeters (6−8 inches) in length. The streaked horned lark has a dark brown back, yellowish underparts, a walnut brown nape and yellow eyebrow stripe and throat. This subspecies is conspicuously more yellow beneath and darker on the back than almost all other subspecies of horned lark. The combination of small size, dark brown back, and yellow on the underparts distinguishes this subspecies from all adjacent forms.
Historical Status and
Historically, the streaked horned lark’s breeding range extended from southern British Columbia, Canada, south through the Puget lowlands and outer coast of Washington, along the lower Columbia River, through the Willamette Valley, the Oregon coast and into the Umpqua and Rogue River Valleys of southwestern Oregon.
The streaked horned lark has been extirpated throughout much of its range, including all of its former range in British Columbia, Canada, the San Juan Islands, the northern Puget lowlands, the Washington coast north of Grays Harbor, the Oregon coast, and the Rogue and Umpqua Valleys in southwestern Oregon.
The current range of the streaked horned lark can be divided in to three regions: (1) the Puget lowlands in Washington, (2) the Washington coast and lower Columbia River islands (including dredge spoil deposition sites near the Columbia River in Portland, Oregon), and (3) the Willamette Valley in Oregon.
An analysis of recent data estimates the current rangewide population of streaked horned larks to be about 1,170–1,610 individuals (Altman 2011). There are about 900–1,300 breeding streaked horned larks in the Willamette Valley (Altman 2011). The largest known populations of streaked horned larks breed in the southern Willamette Valley at the Corvallis Municipal Airport and on the Fish and Wildlife Service’s Willamette Valley National Wildlife Refuge Complex.
Horned larks are birds of wide open spaces with no trees and few or no shrubs. The streaked horned lark nests on the ground in sparsely vegetated sites dominated by grasses and forbs. Historically this type of habitat was found in prairies in western Oregon and Washington, in dune habitats along the coast of Washington, on the sandy beaches and spits along the Columbia and Willamette Rivers, and in grasslands, estuaries, and sandy beaches in British Columbia. Today the streaked horned lark nests in a broad range of habitats, including native prairies, coastal dunes, fallow and active agricultural fields, wetland mudflats, sparsely-vegetated edges of grass fields, recently planted Christmas tree farms with extensive bare ground, moderately- to heavily-grazed pastures, gravel roads or gravel shoulders of lightly-traveled roads, airports, and dredge deposition sites in the lower Columbia River. Wintering streaked horned larks use habitats that are very similar to breeding habitats.
A key attribute of habitat used by larks is open landscape context. Our data indicate that sites used by larks are generally found in open (i.e., flat, treeless) landscapes of 120 hectares (ha)(300 acres) or more. Some patches with the appropriate characteristics (i.e., bare ground, low stature vegetation) may be smaller in size if the adjacent fields provide the required open landscape context. This situation is common in agricultural habitats and on sites next to water. For example, many of the sites used by larks on the islands in the Columbia River are small, but are adjacent to open water, which provides the landscape context needed. Streaked horned larks are found at many airports within the range of the subspecies; as native prairies and scoured river beaches in the Pacific Northwest have declined, airports, with their large area requirements and treeless settings, have become magnets for streaked horned larks.
Nesting begins in late March and continues into late August. The nest
consists of a shallow depression built in the open or near a grass
clump and lined with fine dead grasses. The female commonly lays
four greenish or grayish eggs speckled with brown. Incubation
is only 11 days and the young are able to fly within 9 to 12 days
Larks eat a wide variety of seeds and insects, and appear to select habitats based on the structure of the vegetation rather than the presence of any specific food plants.
Reason for Decline
There are many ongoing threats to the streaked horned lark’s habitat throughout its remaining range from conversion to agriculture and industry, loss of natural disturbance processes, such as fire and flooding, followed by encroachment of woody vegetation, invasion of coastal areas by nonnative beachgrasses, and incompatible management practices. The continued loss and degradation of its scarce habitat could push the subspecies closer to rangewide extinction.
Other threats include inbreeding depression, low reproductive success, and declining population size, which have been documented in the Puget lowlands population; without substantial efforts to stem the decline, larks may disappear from the Puget lowlands. Other ongoing threats from aircraft strikes and training activities at airports have been documented, and put lark populations at risk of further population declines throughout the range of the subspecies.
An interagency group, the Streaked Horned Lark Working Group, has been active for the past several years; the focus of the group has been to develop a better understanding of the streaked horned lark’s biology and the current threats facing the subspecies. Members of the Working Group have worked with land owners and managers throughout the range of the lark to encourage measures to improve habitat quality and minimize activities that could reduce nesting success. Land managers are encouraged to maintain open habitats with low stature vegetation, and to avoid disruptive management activities during the breeding season. Measures to protect streaked horned larks have been incorporated into the Comprehensive Conservation Plans for the Willamette Valley National Wildlife Refuge Complex and the Willapa National Wildlife Refuge.
References and Links
Altman, B. 2011. Historical and Current Distribution and Populations of Bird Species in Prairie-Oak Habitats in the Pacific Northwest. Northwest Science, 85(2):194-222.