Reproductive Success of Streaked Horned Larks (Eremophila alpestris strigata) in Oregon’s Varied Agricultural Landscape: Mid-Willamette Valley

For imperiled organisms, it is unwise to restore/manage landscapes for the most heavily occupied habitat types without first assessing whether the contribution to population growth/stability is commensurate with their apparent suitability (i.e., whether these habitats act as ‘ecological traps’). For example, although larks nest commonly in marginal agricultural fields in Benton County, these fields are often the target of late spring or summer soil/vegetation management practices that destroy eggs and young or cause adult females to abandon their nests. Reliable measures of reproductive success from the habitat types listed above will allow landscape management projects to focus on those habitats that maximize annual recruitment of new breeders, and will inform decisions about how restoration projects can manage restored natural areas for productive breeding of streaked horned larks. When values of habitat-specific reproductive success and factors affecting reproductive failure are identified, it will become possible to effectively design habitat restoration programs and incentive-based agricultural conservation programs that will reverse STHL decline in the Willamette Valley.

What follows details the results of fieldwork conducted in the southeastern Willamette Valley during breeding season 2008. This work was designed to identify habitat- and locality-specific values of reproductive success, to identify variables, if any, that are associated with reproductive success, and to identify direct sources of reproductive failure.