Abstract
Survival value of different parts of the fundamental niche of the redwinged blackbird was determined by comparing nesting success in marsh and upland habitats. Marsh nesting populations had greater success than those in uplands because of a smaller proportion of nests destroyed by predators. Predation pressure in marshes was negatively correlated with the depth of water beneath the nest, and the synchrony and density of nesting in marshes in some cases has a swamping effect on local predator populations. The structure and phenology of marsh compared with upland vegetation is an important factor in determining nesting density and synchrony.Growth rates of nestlings and weight at fledging are similar between habitats. Genetic separation between marsh and upland populations is unlikely. Territoriality probably results in a limitation to breeding density in both habitats.The results support the hypothesis that where sympatric, redwings are excluded from their optimal niche space by yellow-headed blackbirds.
Published Version
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