Streaked Horned Lark (Eremophila alpestris strigata) Fecundity, Survival, Population Growth and Site Fidelity PDF Format - [1.03MB] Related Links: Washington State Status Report for the Mazama Pocket Gopher, Streaked Horned Lark, and Taylor's Checkerspot Range-wide Streaked Horned Lark (Eremophila alpestris strigata) Assessment and Preliminary Conservation Strategy Streaked Horned Lark Monitoring, Habitat Manipulations, and a Conspecific Attraction Experiment Acknowledgments We thank C. Ames, H. Anderson, T. Chestnut, A. Clason, A. Emlen, H. Halbritter, M. Hopey, M. Martin, M. Mossop, M. Pett, L. Sampson, C. Sundstrom, M. Tomlinson and L. Wenn for field assistance. For research on the Pallid horned lark, funding was provided by the Natural Sciences and Engineering Research Council of Canada (NSERC postgraduate scholarship to A.F. Camfield, NSERC Discovery and Northern Research Supplement grants to K. Martin), the Northern Scientific Training Program (to A.F. Camfield, A. Clason and M. Martin), American Ornithologists’ Union (Student Research Award to A.F. Camfield), Environment Canada (Science Horizons grant to A.F. Camfield), and University of British Columbia (graduate fellowship to A.F. Camfield). For research on the streaked horned lark, funding was provided by U.S. Fish and Wildlife Service, Ft. Lewis, McChord Air Force Base, The Nature Conservancy, and Washington Departments of Fish and Wildlife, Natural Resources and Transportation. We would also like to thank Ft. Lewis, McChord Air Force Base, Shelton Airport, Olympia Airport, Washington State Parks, and U.S. Fish and Wildlife Service for allowing access to the study sites. M. Drever provided valuable statistical advice.

Streaked Horned Lark (Eremophila alpestris strigata) Fecundity, Survival, Population Growth and Site Fidelity: Research Progress Report Scott F. Pearson, Alaine F. Camfield, and Kathy Martin January 2008 Abstract Estimates of population growth rate (lambda, λ = 0.61±0.10 SD) indicate that the streaked horned lark (Eremophila alpestris strigata) population is declining rapidly (40% per year). This estimate includes only vital rates from populations in the Puget lowlands, lower Columbia River and the Washington coast and does not include rates from populations in the Willamette Valley of Oregon. Estimates of immigration are not built into our estimates of lambda and as a result, the decline in absolute population size could be less than 40% per year if the population is being rescued by immigration. This rapid population decline is apparently the result of both low fecundity and low survival. The low fecundity (0.91 female fledglings/female/year) was the result of low egg hatchability, fledging success, high clutch depredation, and long intervals between initial nests that failed and re-nests. Adult survival (0.51±0.06, n =58) was also quite low, while juvenile survival (0.16±0.04, n = 88) was relatively high. We compared survival, fecundity and population growth rate between E. a. strigata and another subspecies of horned lark, the pallid horned lark (E. a. articola), located in a relatively healthy ecosystem near Smithers, B.C. Canada. Although the breeding season was more than twice as long for E. a. strigata in Washington, E. a. articola in British Columbia produced 35% more fledglings per egg laid and the net result was higher annual fecundity for E. a. articola. Adult survival was 18% higher and juvenile survival was 13% higher (without dispersal – see below) for E. a. articola. This contemporaneous comparison using nearly identical methods between closely related subspecies lends further support to our estimate of a declining streaked horned lark population throughout a large proportion of its geographic range. Adult survival had the greatest influence on population growth rate for E. a. strigata suggesting that conservation actions that improve adult survival are likely to have the greatest benefit to E. a. strigata. Adult E. a. strigata exhibited extremely high site fidelity (no breeding dispersal observed among regions). We observed examples of E. a. strigata natal dispersal with juveniles moving from the Puget lowlands to the Washington coast and lower Columbia River to breed. Because we did not observe examples of natal or breeding dispersal into the Puget lowlands and because this population is apparently declining and continuing to experience threats, there appears to be a high probability that E. a strigata populations will be extirpated in this region in the near future unless this trend is reversed.