Streaked horned lark abundance and trends for the Puget lowlands and the lower Columbia River/Washington Coast, 2010-2018

The streaked horned lark (Eremophila alpestris strigata) is a partially migratory subspecies associated with sparsely vegetated grassland habitats (Beason 1995, Stinson 2005, Altman 2011) and is listed as threatened under the Endangered Species Act. It is also listed as endangered by the state of Washington and in Canada (Canadian Species at Risk Act 2002). The breeding range of streaked horned lark has contracted over time, with local extirpation from the northern (Puget trough, southern British Columbia, and the Washington Coast north of Grays Harbor) and southern (Rogue River Valley of Oregon) extremes of their range (Beauchesne and Cooper 2003, Stinson 2005, Altman 2011). The current breeding range includes agricultural habitats and grasslands of the Willamette Valley of Oregon, dredge deposition islands along the lower Columbia River, southern Washington coastal dune habitats, and grasslands in the Puget lowlands near Olympia and Tacoma, Washington.

Estimates of survival and fecundity from the mid-2000s indicated streaked horned lark populations in Washington were declining rapidly (Camfield et al. 2011). To provide more up to date population assessments, we developed a monitoring strategy (Pearson et al. 2015) detailing protocols for transect based monitoring that we have been implementing since 2010 on permanently occupied sites. Here we assess abundance and trends using this protocol in two geographic strata (1) Puget Sound region (sites in Pierce, Thurston, and Mason counties), and (2) Lower Columbia River and Washington coast using an analytic method that addresses issues of detectability. The goal of this monitoring effort is to assess changes in abundance and trend of this rare and declining subspecies and to provide critical information for making informed management decisions.