Nest-site selection and reproductive success of Common Yellowthroats in managed Iowa grasslands

Birds are expected to select nest sites that maximize their reproductive success. In some settings, particularly in human-modified landscapes, birds may make maladaptive choices based on unreliable cues. We studied nest-site selection and the factors that influence reproductive success of Common Yellowthroats (Geothlypis trichas) in managed switchgrass (Panicum virgatum) grasslands in Iowa. We compared vegetation variables at 115 nest sites and corresponding random points. Conditional logistic regression was used to relate nest success, brood parasitism, and number of young fledged per successful nest to vegetation characteristics. Common Yellowthroats selected nest sites with denser and more senescent vegetation, and more forb cover compared with random points. Nest success, however, was negatively related to forb cover. Brood parasitism was not well-explained by any variables. Number of young fledged was positively related to the proportion of senescent vegetation. Selection of nest sites with denser vegetation and more senescent vegetation is consistent with variables reported in the literature and emphasizes the importance of nonharvested areas for Common Yellowthroats in switchgrass fields. Maladaptive preference for nest sites with more forbs could have negative consequences for Common Yellowthroat populations if the pattern we saw persists or applies to other settings.