Abstracts

Presented by Todd Arnold - Email: arnol065@umn.edu

Fecundity estimates for demographic modeling are difficult to acquire at the regional spatial scales that correspond to climate shifts, land use impacts or habitat management programs, yet are important for evaluating such effects. Widely available age ratios from late-summer banding data present an underutilized opportunity to examine a regional fecundity index with broad temporal replication. We used age ratios from banding data and hierarchical mixed-effect models to examine how fecundity of five North American dabbling duck species was affected by temporal variation in hydrological cycles, intra- and inter-specific density dependence and alternate prey availability, and whether those relationships were consistent across a broad geographic area. Ecological covariates explained between 16 and 53% of the temporal variation in fecundity. Increasing wetland inundation and an indicator of vole population irruptions were consistent predictors of increasing fecundity across all species. Species exhibited mixed positive and negative responses to interspecific and intraspecific breeding pair densities hypothesized to affect nest and brood survival respectively. Declines in fecundity over time and across space may reflect stronger policies for grassland and wetland protection in the U.S. versus Canadian portions of the prairies. Maintaining the capacity of less permanent basins to rehydrate in wetter periods benefits fecundity. Age ratios at capture could be useful as a fecundity metric in integrated population models and for evaluating population dynamics of extensively banded species, especially if adjusted for capture vulnerability using within-season recapture data.