American black duck brood habitat use and survival in North Carolina
Date
2023
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Publisher
University of Delaware
Abstract
Duckling survival is a major component of waterfowl productivity and is especially important in species like the American black duck (Anas rubripes), which has populations that are below the North American Waterfowl Management Plan goals. I captured and radio-marked 13 female black ducks and 39 ducklings during the 2020 and 2021 breeding seasons to quantify the fine scale breeding season movements, habitat use, and duckling survival in coastal North Carolina. The mean initial movement distance of marked broods from the nest was 490.02 m (95% CI = 329.45⎯650.59). Broods did not select open water, high marsh, low marsh, mudflat, or open water habitat types at random within their home ranges (λ = 0.35, P < 0.01). However, open water was the only habitat type significantly avoided (t11 = -6.19, P < 0.01). On a microhabitat scale, broods used areas with significantly more litter, bare ground (t630 ≥ 2.01, P ≤ 0.05), and less water than available areas (t630 = -3.45, P < 0.01). The estimated daily survival rate (DSR) of ducklings was 0.914 (95% CI, 0.88⎯0.93) based on the null model. The best approximating model indicated that survival improved with increased use of pools and creeks within coastal salt marshes. Hen age also explained most of the variation in DSR with younger female hens leading to greater survival. Duckling production would benefit from minimizing human disturbance on natural islands in the Pamlico Sound and implementing predator management programs in mainland brackish marshes in Hyde County.
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Keywords
Anas rubripes, Duckling survival, Black ducks, Water habitats, Predator management