Change in Density of Duck Nest Cavities at Forests in the North Central United States

Abstract

During the past century, clear-cut hardwood forests of the north central United States have regenerated, and trees have matured into size classes increasingly capable of producing cavities suitable for nesting ducks. We determined the density of natural cavities suitable for cavity-nesting ducks, compared suitable cavity-tree distribution by size class and species, and assessed how forest maturation impacted suitable cavity density and distribution over time at four sites in the north central United States. During 2006–2008, cavities suitable for nesting ducks occurred at densities of 1.76, 1.40, 1.84, and 0.92/ha at Mingo National Wildlife Refuge (NWR) in Missouri, Shiawassee NWR in Michigan, Muscatatuck NWR in Indiana, and a study site including Mead State Wildlife Area in Wisconsin, respectively. Suitable nest-cavity densities increased at Mingo NWR (+300%) since 1965 and Shiawassee NWR (+900%) since 1973, but they remained similar at study sites examined during the mid-1980s (Muscatatuck NWR and Mead Wildlife Area) when previous site-specific cavity-suitability criteria were applied to our cavity data. Differences among sites were due to variation in tree species composition, stage of forest maturation, and potentially forest harvest regimes. Comparison of size distributions of all trees and those with suitable nest cavities indicated these forests have yet to mature into the most prolific cavity-producing size classes. Our findings suggest nest sites are not limiting duck populations at these four sites and hardwood forests with similar composition and structure. Rather than using the traditional practice of supplementing duck nest sites, wildlife managers in the North Central region should assess actual limiting factors before developing habitat management prescriptions for local cavity-nesting duck populations.

LiDAR and multispectral imagery predict the occurrence of tree cavities suitable for a cavity‐nesting duck

“…Accordingly, the relationships between specific predictors and cavity presence generally agreed with our understanding of the tree and forest characteristics related to cavity development. For example, similar to the most important classes of Cover in our analysis, northern hardwoods, and to a lesser extent, aspen and oak species, are known to be most likely to produce cavities in northcentral USA (Denton et al, 2012a;. Higher standing volume (Vol), basal area (SBA), and site-index (SI) are indicative of higher numbers of large trees that grow more quickly and, hence, potential cavity-bearing trees (Carey, 1983;Gilmer et al, 1978).…”

“…The spatial location of potential nest sites is particularly important for Wood Ducks, as they also depend on proximate shallow wetlands for their other habitat needs. Wood Ducks are a relatively large‐bodied secondary cavity nester, requiring cavities with entrances ≥6 cm in diameter, vertical depths of >10 cm, and nesting platforms ≥14 × 15 cm (Denton et al., 2012a). A variety of other wildlife from raptors to squirrels to mustelids have overlapping cavity needs (Pfannmuller et al., 2017; Pöyry, 1994).…”

“…The data were projected into North American Datum 1983 UTM Zone 15N. requiring cavities with entrances ≥6 cm in diameter, vertical depths of >10 cm, and nesting platforms ≥14 9 15 cm (Denton et al, 2012a). A variety of other wildlife from raptors to squirrels to mustelids have overlapping cavity needs (Pfannmuller et al, 2017;P€ oyry, 1994).…”

Temporal change in abundance of potential nesting cavities for wood ducks (Aix sponsa) in Northern Minnesota, United States

“…Wood ducks (Aix sponsa) nest throughout much of temperate Eastern and parts of Western North United States (Hepp and Bellrose, 2013), usually in the cavities of largediameter deciduous trees (Bellrose and Holm, 1994). Tree cavities are not thought to be limiting to the breeding populations of cavity-nesting ducks in the Upper Midwest (Denton et al, 2012a), but the formation of these structures can be a slow process (Bellrose and Holm, 1994). The selection of nest sites is attributable to habitat-related cues (Berg and Eadie, 2020).…”

“…The availability of stems containing cavities suitable for nesting wood ducks has been estimated using published bounds values and attributes in follow-up studies. Specifically, the proportions of stems in each tree-species-and DBH-class that had suitable nesting cavities were estimated in these investigations (Denton et al, 2012a;Zlonis et al, 2020). Tree health status (3 classes: dead, live-health impacted, live-healthy) was an important influence on the probability of suitable-cavity occurrence (hereafter, P occurrence), with dead stems having the greatest probability, closely followed by live-health impacted stems (i.e., those with defects that suggest a decline in health), and finally, live-healthy stems (Zlonis et al, 2020).…”