Abstracts

Presented by Gillie D. Croft - Email: gcroft@clemson.edu

We conducted surveys of nest-structure use and selection by wood ducks (Aix sponsa) and black-bellied whistling ducks (Dendrocygna autumnalis) across two coastal South Carolina regions during 20162017. For 364 and 354 nest boxes surveyed each year, 61% were used by wood ducks and 15% by black-bellied whistling ducks. Peak nesting for wood ducks was in March-April and June-August for black-bellied whistling ducks, suggesting limited overlap in nesting chronology and competition for nest boxes between species. Multiple logistic regression revealed the odds of nest-box use by wood ducks were 5.8% (P = 0.003) greater for every 1,000 cm3 decrease in internal box volume. However, odds of nest-box use by black-bellied whistling ducks were 19.6% (P < 0.001) greater for every 1,000 cm3 increase in internal volume. Odds of box use were 15.1% and 11.1% greater (0.001 P 0.024) for wood ducks and black-bellied whistling ducks, respectively, for every 10% decrease in percent canopy cover around boxes. Odds of nest-box use by black-bellied whistling ducks were 18.3% and 9.8% greater (0.004 P 0.005) for every 10-cm increase in distance from the base of boxes entrance vertically to ground or water surface and every 10-m decrease in distance between boxes, respectively. Our results suggest the conventional nest box described by F. C. Bellrose, with internal dimensions of 25 25 55 cm, accommodated both species and can be deployed where the species nest sympatrically. Additionally, we suggest nest-box entrance diameter be 13 cm to facilitate use by larger bodied black-bellied whistling ducks but maintain use by wood ducks. Lastly, we observed that both species of ducks used boxes in open canopy ponds, which often contained fish that prey on ducklings. We suggest avoidance of these wetlands for erection of nest structures.