Local and Landscape Influence on Red-winged Blackbird ( Agelaius phoeniceus) Nest Success in Great Lakes Coastal Wetlands

Abstract

Nest predation has been identified as the primary mechanism contributing to reduction of reproductive success for the marsh-breeding red-winged blackbird ( Agelaius phoeniceus). Differences in rates of nest predation have been linked to nest site characteristics within a wetland, primarily water depth. However, the relationship between the landscape surrounding these habitats and the probability of nest predation is uncertain. Moreover, factors associated with reproductive success could be a potentially powerful indicator of ecological condition in wetland habitats. We investigated the influence of landscape pattern on nest success by monitoring 366 red-winged blackbird nests in 11 coastal wetlands along the south shore of Lake Superior. Of the 366 nests, 39% were successful, 56% failed, and 5% were abandoned or lacked sufficient evidence to determine nest fate. Nest predation accounted for over 93% of total failures. Predation rates ranged from 31% to 97% among the 11 wetland sites. We modeled nest predation using multi-model logistic regression analysis and the Akaike information criterion to identify and parameterize influential variables derived from the nest site, wetland, and landscape surrounding each wetland. Our results indicated that landscape variables comprised over 50% of model prediction weight in 15 of the 17 models. Nest failure was highest at sites within an urban/residential landscape matrix. Reproductive success could be a good indicator of the ecological health of Great Lakes wetlands.