Wood duck reproductive success and brood ecology from artificial nest boxes in the Delmarva Peninsula
Date
2025
Authors
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Publisher
University of Delaware
Abstract
Wood Ducks (Aix sponsa) nesting in artificial nest boxes have received considerable research attention throughout the last century. However, spatial and habitat differences among these studies have confounded results and necessitate further study, particularly in the Mid-Atlantic where data is limited and both inland forested wetlands and coastal open marsh habitats support populations of Wood Ducks. I analyzed nesting records from 2020–2023 and assessed the relative influence that 22 box physical characteristics and surrounding habitat attributes had in determining nest box use, nest parasitism, and nest success. During 2023–2024 I deployed 79 GPS-UHF-VHF transmitters on hen Wood Ducks and 237 VHF prong and suture transmitters on ducklings to monitor third-order habitat selection, movement behavior, and 30-day duckling survival in both habitat types. Boxes in the Inland habitat that had 60–70 cm2 entrance areas and were placed in areas with >30 cm of water received the most use and attributes that made boxes more likely to be used also increased the probability that nests within them were parasitized. Parasitism did not have a severe impact on nest success and clutch size was strongly related to the probability of success in the Inland habitat. Newer boxes placed in >75 cm of water, with entrances > 2 m above water, and that were >200 m from another box were used the most in the Coastal habitat. Boxes that were more visible were more likely to be parasitized in the Coastal habitat, and Coastal boxes that were older, in deeper water, and had greater separation from neighboring boxes were most likely to have successful nests. Broods in both habitats sought out wetland areas with abundant emergent aquatic vegetation and water depths of ~30 cm. Inland broods preferred areas with less canopy cover and Coastal broods opted for areas with lower levels of salinity. Inland broods traveled to more distinct wetlands throughout brood rearing, but Coastal broods moved greater distances on a daily basis. Thirty-day duckling survival was 0.15 (CI 0.08–0.28) in the Inland habitat and 0.21 (CI 0.12–0.37) in the Coastal habitat. Rainfall had the largest impact on duckling mortality in both habitats where more precipitation increased mortality. Lower minimum daily temperatures also increased hazard rate in the Inland habitat. Coastal duckling mortality increased with advancing Julian Date of nest hatch and with larger brood sizes. Although the influence of metrics related to nest and brood success varied between habitats, both can generally be managed with consideration of the same biological principles. Nest boxes should be conspicuous but not visible from neighboring boxes, have small entrance areas, be placed in water to deter nest predation, and be placed in or near wetlands with abundant emergent vegetation. Depending on metrics used to quantify parasitism and success, intraspecific nest parasitism may not appear to be detrimental to Wood Duck nesting but likely has negative implications on duckling survival. The extent of nest parasitism should therefore be closely monitored and discouraged when possible.
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Keywords
Brood, Duckling, Nest box, Parasitism, Wood Ducks