Density, Characteristics, and Use of Tree Cavities for Nesting Waterfowl at Missisquoi National Wildlife Refuge
File(s)
Date
2017-06Author
Malanchuk, John 'Boomer' II
Publisher
University of Wisconsin-Stevens Point, College of Natural Resources
Metadata
Show full item recordAbstract
There are seven species of obligate, secondary cavity-nesting waterfowl in North America which rely on abiotic (e.g. high winds) and biotic (e.g. woodpecker excavations) disturbance events to produce tree cavities for successful nesting. The density and use of these cavities is poorly understood in the northeastern United States. The Lake Champlain basin is one of few areas in the U.S. where wood ducks (Aix sponsa), hooded mergansers (Lophodytes cucullatus), and common goldeneyes (Bucephala clangula) breeding ranges overlap and, therefore, likely compete for nest sites.
My study represents the first tree cavity density estimate in the northeastern U.S. In 2015, in the old-growth silver maple (Acer saccharinum) floodplain forest at Missisquoi National Wildlife Refuge (MNWR), fixed-area plots estimated 2.5 cavities/ha (95% CI = 0.3 – 4.7). In 2016, line-transect methodology estimated 0.39 cavities/ha (95% CI = 0.18 – 0.84); a new method for estimating tree cavity density. Line-transect methodology provides more precise results with less in-field effort.
No nest success was observed in natural tree cavities in 2015 or 2016 while nests from boxes were successful (2015 = 61%, 2016 = 27%). As such, nest boxes likely remain and important management tool in waterfowl production at Missisquoi National Wildlife Refuge. Cavities (n = 12) were more likely to be occupied by nesting waterfowl as height from forest floor increased and size of cavity opening decreased; a perceived avoidance from predators (Bellrose and Holm 1994).