Trapping Rates, Survival, and Habitat Selection for Wood Ducks in Central Wisconsin

Abstract

CHAPTER ONE: Wood ducks are one the most common and studied waterfowl species in the Mississippi and Atlantic flyways. However, most research on breeding female populations comes from those nesting in artificial nest boxes. While this capture method might be relatively easy and efficient, it inherently eliminates, or at the very least, reduces the chances of studying wood ducks that nest in natural tree cavities. This seems problematic given most wood ducks do not nest in artificial boxes (Bellrose 1990) and natural cavity availability in the Upper Midwest is increasing annually (Denton et al. 2012). Therefore, my goal was to evaluate trapping wood ducks using decoy traps as an alternative method. I purchased, provided care for, and used 47 domesticated ‘decoy’ wood ducks in 2017 and 2018 at the Mead Wildlife Management Area (WMA) in central Wisconsin to catch wild pre-breeding female wood ducks. I also evaluated capture rates for baited traps and provided use rates for > 100 artificial next boxes that are managed by the Mead WMA staff. I captured females (n=27) in decoy traps in 2017 and 2018. Females were trapped at a rate of 0.08 birds/trap day in decoy traps both years, but I failed to catch any wood ducks in baited traps. I found that smaller decoys captured more wild females. Use rates of artificial nest boxes by wood ducks was 0.09 and 0.07 in 2017 and 2018, respectively, and were historically low. Domestic wood duck husbandry and health testing logistics can be a time and financial limitation. Decoy trapping was the most successful method for capturing pre-nesting wood ducks and the population of birds I captured from them represents a promising alternative to studying solely box-nesting populations.

CHAPTER TWO: Although breeding ecology of wood ducks is well-studied, most research have involved captured birds from artificial nest boxes where females and their offspring might be protected from natural predation. In addition to breeding parameters, most habitat selection studies on wood duck have focused on individuals with confirmed nests. I captured female wood duck priors to nest initiation and from artificial nest boxes, attached VHF transmitters to individuals, and tracked their location throughout the breeding season at Mead Wildlife management area in central Wisconsin during 2017 and 2018. My sample of female wood ducks represented box-nesting (n=16), cavity nesting (n=8), non-nesting (n=5) ducks, and those that I could not determine nests (n=14). I pooled data across years and estimated breeding season female survival at 0.343(95% CI=0.192-0.613), and this did not vary by mass, trap type, nest attempt, or nest type. This survival estimate was the lowest published breeding season survival estimate I could find, indicating that Mead WMA might be a sink for wood duck populations. Further study is warranted to determine if female survival is consistently low at Mead WMA or if these estimates were a function of random environmental stochasticity. Breeding propensity was 0.44 for females captured pre-nesting but could be as high as 0.72 if unknown status wood ducks indeed initiated a nest. Although I followed 16 females from artificial nest boxes over 2 years, they demonstrated limited recruitment (n=1 successful brood to 30 days), calling into question the value of artificial nest boxes, at least at Mead WMA. Not surprisingly, my sample of wood ducks selected for forested and scrub shrub wetlands, but surprisingly, they also selected for 5 additional habitats, including habitats with less structural cover, suggesting managers should maintain diverse wetland complexes. Additional research on wood ducks during the breeding season is needed, especially on cavity- and non-nesting individuals.