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Streaked Horned Lark

Streaked horned lark (Rod Gilbert)

Scientific name:  Eremophila alpestris strigata

Status:  Threatened

Critical Habitat:  Designated

Listing Activity:  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, and critical habitat was designated.

  • Description

    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 6-8 inches (16-20 centimeters) 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 other subspecies of horned lark that occur in Washington and Oregon.  None of the four other subspecies of horned lark in Washington and Oregon breed within the range of the streaked horned lark, but all five subspecies frequently overwinter in mixed-species flocks in the Willamette Valley, Oregon (Marshall et al. 2003).

    Historical Status and Current Trend

    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 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.

    Habitat

    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 300 acres (120 hectares (ha)) 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 due to their large size and flight safety requirement for short vegetation. 

    Life History

    Nesting behaviors begin in late March, with first eggs being laid in April, and continuing into late August.  They will often re-nest in late June or early July. 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 1 to 5 (on average 3) greenish or grayish eggs speckled with brown.  Young streaked horned larks leave the nest by the end of the first week after hatching, and are cared for by the parents until they’re about 4 weeks old, when they become independent.  Nest success is often very low.

    Food

    Streaked horned lark adults eat mainly grass and forb seeds, but they feed insects to their young.  They appear to select habitats based on the structure of the vegetation rather than the presence of any specific food plants.

    Reasons for Decline

    The subspecies has disappeared from all formerly documented locations in the northern portions of its range (see Historical Status and Current Trend, above). The streaked horned lark’s range may be continuing to contract, and the number of streaked horned larks in Washington and on the Columbia River islands is declining. This decline taken together with evidence of inbreeding depression in the south Puget Sound indicates that the streaked horned lark’s range may contract further in the future.  The threat of development and adverse impacts to habitat from conversion to other uses (residential or commercial development, agriculture), loss and degradation of habitat due to fire suppression and subsequent invasion of habitat by undesirable native and non-native plants, dredge deposition timing and placement on Columbia River islands, improperly timed burning and mowing regimes, military training, and conversion of large grass seed production fields to incompatible agricultural commodities are significant and are expected to continue into the foreseeable future.  Many military training impacts are expected to increase under the DOD’s Grow the Army initiative, although Joint Base Lewis-McChord’s Streaked Horned Lark Endangered Species Management Plan provides an overall conservation benefit to the subspecies.

    There are likely to be significant, ongoing threats to the subspecies due to predation, which is the most frequently documented source of mortality for eggs and young, and the primary source of nest failure.  This is especially a concern in the south Puget Sound area, although streaked horned larks in other areas are also susceptible. In addition, we conclude that significant, ongoing threats to the streaked horned lark may occur due to small population effects (for this subspecies, this includes loss of genetic diversity, low survival, and reduced fecundity and nest success).  This is of particular concern in the south Puget Sound area, where such threats in combination with a lack of immigration into that area and high breeding site fidelity could lead to local population extirpations.  Other significant, ongoing threats to the streaked horned lark include existing regulatory mechanisms, which are not adequate to address or reduce threats to streaked horned lark; other activities associated with airports (development and aircraft strikes); and recreation (including but not limited to pedestrians, model airplane flying, dog walking, beachcombing, vehicle or ORV use, camping, and horseback riding in areas occupied by streaked horned lark).

    Conservation Measures

    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, and Joint Base Lewis-McChord’s Streaked Horned Lark Endangered Species Management Plan.

    References

    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

    Marshall, D.B., M.G. Hunter, and A.L. Contreras, Eds. 2003.  Horned lark Eremophila alpestris in Birds of Oregon: A general reference.  Oregon State University Press, Corvallis, OR.  768 pp.

    Pearson, S.F., and B. Altman.  2005.  Range-wide Streaked Horned Lark (Eremophila alpestris strigata) Assessment and Preliminary Conservation Strategy.  Washington Department of Fish and Wildlife, Olympia, WA.  25pp.

    Stinson D.W.  2005.  Status Report for the Mazama Pocket Gopher, Streaked Horned Lark, and Taylor’s Checkerspot.  Washington Department of Fish and Wildlife, Wildlife Program.  Olympia, WA. 145 pp.

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