Washington State Periodic Status Review for the Streaked Horned Lark (2016)

The Streaked Horned Lark (Eremophila alpestris strigata) is a rare endemic subspecies found only in western Washington and Oregon. It is perhaps the most distinct subspecies of the Horned Lark, a common ground-dwelling passerine of open grassland habitat. The Streaked Horned Lark was listed as endangered by the State of Washington in 2006, and as threatened under the federal Endangered Species Act by the U.S. Fish and Wildlife Service in 2013 (USFWS 2013).

The Streaked Horned Lark was once more abundant and widespread, but has become increasingly rare with habitat declines and is now restricted to a few large open grassland and sparsely vegetated sites, including airports, sandy islands, and coastal spits. The Streaked Horned Lark is currently known to breed at up to17 locations in Washington; 8 in the southern Puget Sound region; 6 sites on the outer coast; and 4 on islands and shore sites along the lower Columbia River. Oregon breeding areas include up to 11 along the lower Columbia, as well as airports and agricultural fields in the Willamette Valley.

Based on detections of singing males during standardized surveys, approximately 147 pairs were present at known Washington sites in 2015. Density trends from standardized transect data for 2010â€"2014 suggested that the populations at most sites were stable. However, the male population appears to be increasing and the female population appears to be decreasing on some Puget lowland sites resulting in a skewed sex ratio. This could result from sex ratios at hatching, or if females were subject to higher mortality rates. Numerous factors affect larks including predation of nests and fledglings, human-related disturbance and mortalities (at airports, army training areas, and nesting beaches), and likely low genetic diversity caused by inbreeding in small populations with high site fidelity. In addition, toxic substances may present a hazard to Streaked Horned Larks; these include zinc phosphide, used to control rodents, and seeds treated with pesticides to control pests and fungus.

The subspecies is the focus of concerted conservation efforts with several key partners involved, including Joint Base Lewis-McChord, Center for Natural Lands Management, U.S. Army Corps of Engineers, civilian airports (e.g. Corvallis, Olympia, and Shelton), Oregon State University, U.S. Fish and Wildlife Service, American Bird Conservancy, Port of Portland, and The Evergreen State College. Conservation actions include protecting nests and fledglings at nesting areas, restoring habitat, genetic augmentation of an at-risk population, and experiments to attract larks to new locations.

Joint Base Lewis-McChord has collaborated with Center for Natural Lands Management to monitor lark nests to help minimize impacts of mowing and training activities on nesting, and lark reproductive success improved in 2014 and 2015; no nests were lost to human-related causes in 2015. The Army Corps of Engineers recently committed to maintain and increase lark habitat at Columbia River dredged material deposition sites. These actions have improved the outlook for lark recovery. However, with a range-wide population estimated at 1,170â€"1,610 individuals, including fewer than 150 pairs in Washington, it is recommended that the Streaked Horned Lark remain listed as an endangered species in Washington.