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Monday, January 29 • 3:20pm - 3:40pm
SYMPOSIA-04: Beyond Wetlands: The Importance of Grassland Habitat for Breeding Waterfowl in an Agricultural Landscape

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AUTHORS. Tyler M. Harms, Iowa Department of Natural Resources and Iowa State University; Orrin E. Jones III, Iowa Department of Natural Resources; Stephen J. Dinsmore, Iowa State University; Rex R. Johnson, Iowa Department of Natural Resources

ABSTRACT. Landscape composition can influence many aspects of waterfowl life histories including dispersal, reproductive success, and recruitment. However, little is known about the potential influence of landscape composition on breeding waterfowl densities, particularly on Iowa wetlands that are situated in a highly altered landscape. We used data from aerial surveys in Iowa collected as part of the annual 4-Square-Mile Survey of breeding waterfowl coordinated by the U.S. Fish and Wildlife Service from 2006-2014. Using National Land Cover Database (NLCD) from 2011, we calculated values of percentage of the landscape, patch density, largest patch index, and interspersion-juxtaposition index for seven habitat classes (wetland, water, grassland, hayland, pasture land, woodland, and agriculture). Landscape covariates were calculated within a 500 m, 1000 m, 1500 m, and 3000 m radius of our sampled wetlands. We modeled the number of indicated pairs per wetland as a function of all individual covariates for two common breeding duck species in the Iowa PPR: Mallard (Anas platyrhynchos) and Blue-winged Teal (Anas discors). All landscape covariates were modeled with additive effects of wet area and the square root of wet area to account for variation in annual wetland conditions. Grassland patch density at both the 500 m and 1000 m scales was positively correlated with breeding pair density of both Mallard (β = 0.11, SE = 0.04) and Blue-winged Teal (β = 0.38, SE = 0.13), respectively. Currently, the model used to estimate breeding duck populations in Iowa uses only annual wetland conditions to predict breeding duck densities. Our study illustrates the importance of thinking beyond wetlands and considering not just amount of grassland habitat, but how grassland habitat is distributed among patches to provide the most benefit to upland nesting ducks in an agricultural landscape.

Monday January 29, 2018 3:20pm - 3:40pm CST