Demography of Eastern Yellow Wagtails at Cape Romanzof, Alaska

Abstract

We quantified demographic parameters of Eastern Yellow Wagtails (Motacilla tschutschensis) breeding at Cape Romanzof, Yukon Delta National Wildlife Refuge, Alaska. We monitored 79 nests in an 837-ha area during 1997–1999 and banded 160 individuals. Mayfield nest success differed among years and ranged from 0.14 to 0.63/year. Most nest failures were attributed to predation. Annual fecundity (mean number of fledglings/female) ranged from 0.7 to 3.7. At least 8.8% of nests had polygynous males; females paired with polygynous males had the same fecundity as monogamous females. Forty-two to 100% of the breeding males returned the following year, usually to the same territory while no adult females returned. Four nestlings banded in the study area returned to nest the following year. The best model for annual survival accounted for differences between both age groups and years. The demography of Eastern Yellow Wagtails at Cape Romanzof varied and was characterized by relatively high adult male survival and site fidelity, female-biased dispersal, and weak natal philopatry. The absence of returning females is significant and possible differences in migration stopovers and wintering locations should be investigated. Moderate levels of male immigration may be necessary in periodic pulses to maintain a local population, but female immigration would need to be massive and sustained.