Nest‐Box Use by Wood Ducks and Black‐Bellied Whistling Ducks in Coastal South Carolina

Abstract

We surveyed nest-structure use by sympatric nesting wood ducks (Aix sponsa) and black-bellied whistling ducks (Dendrocygna autumnalis) across coastal South Carolina, USA, in 2016-2017. Of 718 nest boxes surveyed cumulatively in 2016 and 2017, 61% were used by wood ducks and 15% by black-bellied whistling ducks. Lower nest-box use by whistling ducks was related to recent arrivals and breeding by the species in South Carolina. Nest-box use by wood ducks was 6% greater for every 1,000-cm 3 decrease from the mean internal box volume of all boxes monitored, whereas use by black-bellied whistling ducks was 20% greater for every 1,000-cm 3 increase from the mean internal volume of all boxes. Box use was 15% and 11% greater by wood ducks and black-bellied whistling ducks, respectively, for every 10% decrease from the mean percent canopy cover of all nest boxes. Nest-box use by black-bellied whistling ducks was 18% and 10% greater for every 10-cm increase from the mean distance from the base of a box's entrance vertically to the ground or water and every 10-m decrease from the mean distance to the nearest box for all boxes monitored, respectively. Our results suggested nest boxes with internal volumes of~15,000-31,000 cm 3 were most used by wood ducks, but the conventional nest box with an internal volume of 34,375 cm 3 and internal dimensions of 25 × 25 × 55 cm accommodated wood ducks and black-bellied whistling ducks, and can be deployed where the species are sympatric. However, where black-bellied whistling ducks occur, the diameter of an entrance hole for nest boxes should be 13 cm to allow passage by the larger bodied species. We suggest a need for research to estimate recruitment rates for box-nesting females and cost effectiveness of box programs based on female recruitment.

Louisiana Black-bellied Whistling-Duck clutch characteristics in the presence of conspecific and interspecific brood parasitism

“…Thus, as facultative cavity-nesters, Whistling-Ducks have the potential to interact and compete for nest sites with other cavity nesting species, such as the Wood Duck (Aix sponsa). Croft et al (2020) identified substantial niche overlap in both nest box preferences and timing of nesting in South Carolina, where Wood Ducks nested January to July and Journal of Field Ornithology 93(4): 8 https://journal.afonet.org/vol93/iss4/art8/ Whistling-Ducks nested May to September. Given the temporal overlap in nest box use (Croft et al 2020) and that both species are conspecific brood parasites (McCamant and Bolen 1979, Semel et al 1988, James 2000, there is potential for interspecific brood parasitism (IBP) to occur.…”

“…Croft et al (2020) identified substantial niche overlap in both nest box preferences and timing of nesting in South Carolina, where Wood Ducks nested January to July and Journal of Field Ornithology 93(4): 8 https://journal.afonet.org/vol93/iss4/art8/ Whistling-Ducks nested May to September. Given the temporal overlap in nest box use (Croft et al 2020) and that both species are conspecific brood parasites (McCamant and Bolen 1979, Semel et al 1988, James 2000, there is potential for interspecific brood parasitism (IBP) to occur. A single instance of Whistling-Ducks parasitizing Wood Duck nests has been documented in the literature based on two mixed clutches that were incubated by Wood Ducks (Bolen and Cain 1968); there are no publications that document Wood Ducks laying parasitic eggs in Whistling-Duck nests.…”

“…However, their range began expanding northward in the middle part of the 20th century, with individuals commonly sighted in Arizona, Louisiana, and Florida by the 1960s (Baldassarre 2014). By the early 2000s, breeding populations had also been established in Arkansas, Oklahoma, Tennessee, and South Carolina (Bergstrom 1999, Baldassarre 2014, Cohen et al 2019, Croft et al 2020, and since then, Whistling-Ducks have been documented breeding as far north as Wisconsin and Nebraska, and pioneering individuals observed as far north as central Quebec (https://ebird.org/home).…”

Nest box-mounted PIT tag readers reveal cryptic recruits of cavity-nesting waterfowl in south Louisiana

“…BBWD are unusual among ducks in that both sexes incubate the nest, and they are facultative secondary cavity-nesters, with nests documented in natural cavities, manmade nest boxes, and on the ground [6][7][8] . As predominately cavity nesters, the expansion of BBWD into the core breeding range of Wood Ducks (Aix sponsa; hereafter, WODU) is potentially of management concern for myriad reasons, including competition for nest sites [9] in areas where breeding phenology of both species overlaps [4,10] . In addition, both conspeci c [11][12][13] and interspeci c [4,14,15] nest parasitism has been documented in BBWD, including parasitism of WODU nests [4] , which has the potential to negatively affect WODU reproductive success by increasing nest abandonment and decreasing egg hatchability [16,17] .…”

Avoiding a conservation pitfall: Considering the risks of unsuitably hot bat boxes: Adding context to Crawford & O'Keefe

“…As noted, initial efforts to aid a species are rarely perfect. Wood duck boxes are a long-term success but are still being improved after nearly 100 years (Croft, 2018); management gets more complex over time. We see use of boxes as an opportunity to help bats not "a risk to be mitigated by policy.…”