Natural Cavities Used by Wood Ducks in North-Central Minnesota

Abstract

Radio telemetry was used to locate 31 wood duck (Aix sponsa) nest cavity sites in 16 forest stands. Stands were of 2 types: (1) mature (t = 107 years) northern hardwoods (10 nest sites), and (2) mature (i = 68 years) quaking aspen (Populus tremuloides) (21 nest sites). Aspen was the most important cavity-producing tree used by wood ducks and accounted for 57 percent of 28 cavities inspected. In stands used by wood ducks, the average density of suitable cavities was about 4 per hectare. Trees containing nests were closer to water areas (P < 0.05) and the nearest forest canopy openings (P < 0.01) than was a random sample of trees from the same stands. A significant (P < 0.005) relationship existed between the orientation of the cavity entrance and the nearest canopy opening. Potential wood duck cavities usually were clustered within a stand rather than randomly distributed. Selection of trees by woodpeckers for nest hole construction probably influenced the availability of cavities used by wood ducks. A plan for managing forests to benefit wood ducks and other wildlife dependent on old-growth timber is discussed. J. WILDL. MANAGE. 42(2):288-298 McCabe (1966) and Aultfather (1966) pointed out the lack of information needed to guide foresters in multiple-use programs beneficial to wood ducks. There is little information on the use of natural cavities by wood ducks, particularly in the northern forested regions of the Lake States. Increases in wood duck populations in certain areas have been attributed to nest boxes (Bellrose et al. 1964, Grice and Rogers 1965), but, in some forested areas, large scale nest box programs may not be practical. Furthermore, timber resources that can provide a sustained source of cavity sites may be available. The primary objectives of this paper are to describe: (1) the home range of wood duck hens in relation to the nest site, (2) features of the habitat used by the nesting pair and characteristics of the forest stands containing cavity trees, (3) characteristics of the cavity tree and its immediate surroundings, and (4) guidelines for foresters managing northern forests to consider in formulating multiple use programs that would benefit wood ducks and other cavity-dwelling wildlife species. We thank H. A. Doty for critically reviewing the manuscript and W. A. Aultfather and G. W. Gullion for providing suggestions in manuscript preparation. E. Johnson provided assistance in photo interpretation and in the description of forest site conditions. T. S. Klodfelter and R. S. Stott assisted with data collection. We were assisted in statistical analyses by D. H. Johnson and in computer processing by D. A. Davenport. Telemetry equipment was constructed and maintained by the engineering staff, Cedar Creek Bioelectronics Lab, University of Minnesota. 1This research was supported by the U.S. Fish and Wildlife Service, University of Minnesota, National Institute of Health Training Grant TO1-GM01779, and the U.S. Energy Research and Development Administration (C00-1332-126). 2 Present address: U.S. Fish and Wildlife Service, Northern Prairie Wildlife Research Center, Jamestown, North Dakota 58401. 3 Present address: Department of Zoology, Washington State University, Pullman 99163. 4 Present address: R.R. #1, Valmeyer, Illinois 62295. 288 J. Wildl. Manage. 42(2):1978 This content downloaded from 157.55.39.104 on Sat, 18 Jun 2016 06:48:44 UTC All use subject to http://about.jstor.org/terms WOOD DUCK USE OF NATURAL CAVITIES .Gilmer et al. 289