Estimates of population growth rate indicate that the streaked horned lark population is declining rapidly (40% per year) in the Puget lowlands, lower Columbia River and the Washington coast. This rapid population decline is apparently the result of both low fecundity and low survival. Adult survival had the greatest influence on population growth rate, suggesting that conservation actions that improve adult survival are likely to have the greatest benefit. Adults exhibited extremely high site fidelity (no breeding dispersal observed among regions). We observed examples of 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.