Abstracts

Presented by Daniel M. Lawson - Email: dlawso@udel.edu

North Carolina represents the southern extent of the American black ducks (Anas rubripes) breeding range; however, their breeding ecology in this region is not fully understood. We located and monitored 140 nesting black ducks over two years (2017-18) to assess nesting productivity and quantify nesting habitat within coastal North Carolina. Specifically, we quantified nest initiation, peak nesting dates, nest success rates, modeled causes of failure, and tested for significant differences in 4th order habitat selection in use versus non-use nesting sites. The average nest initiation date over the study was April 12 with a peak nesting date of April 26. Nest success rates varied from 34.18% (2017, CI=95%, SE=9.83) to 66.40% (2018, CI=95%, SE=7.27) and daily survival rates averaged 97.69% (CI=95%, 96.74, 98.37) over the two years of the study. We designed a priori and ranked 25 competing models of nest failure using program MCestimate. The top-ranking model was fail(MVI*YEAR) where MVI*YEAR= Mainland versus island nesting location interacting with year of the study. Our summed model weight was .67. Primary nest predators included crows (Corvidae), raccoons (Procyon lotor), American mink (Neovison vison), and bald eagles (Haliaeetus leucocephalus). To define 4th order nesting habitat we conducted a simple two-factor t-test of vegetation composition (% grass), density, and average height at the nest and at two random paired points within 50 meters of the nest. Additionally, we tested National Wetland Inventory Classification and elevation at the nest and at two randomly generated points within 50 meters of the nest. We found significant differences (P<0.05) in vegetation composition, density, and average height between use and non-use sites.