McLaughlin, D.M. 1990. Nesting ecology, movements, and habitat usage of breeding hooded mergansers in the Adirondack Mountains. M.S. Thesis, SUNY-ESF, Syracuse, 69 pp.

Abstract: Nesting biology characteristics, adult and brood movements, and habitat usage of a population of hooded mergansers (Lophodytes cucullatus) residing in the Adirondack Mountains of New York were investigated during 1987-1989. Twenty-three nests located in nest boxes were studied. Nesting ecology was similar to previously reported data except the span of nest initiation dates was more narrow, nesting success was higher, and hatchability of eggs in successful nests was lower. Occupancy of available nest boxes by hooded mergansers never exceeded 12% per year. Telemetry data obtained from 8 adult female hooded mergansers revealed an average traveling distance of 1.5 km during incubation recesses. Average post-fledging distance of 11 adult female hooded mergansers was 2.9 km. Eighty percent of the birds monitored during the brood-rearing stage (n = 10) did not take their broods to the wetlands nearest the nest. Secondary moves were detected for only two of the transmittered birds. During brood-rearing, hooded mergansers carrying transmitters were consistently located in relatively small areas. Thus, home ranges during this stage were believed to be small although brief sampling periods and small sample sizes prevented such calculations. Hooded mergansers generally exhibited preferences for beaver ponds and shrub swamps while streams and open water were avoided. Preferences varied by individuals, by year, and by stage (i.e., incubation recess and brood-rearing). Population levels of hooded mergansers in the Adirondack Mountains may be limited due to numerous factors. Evaluation of natural tree cavity abundance, suitable nest box construction and location, adult mortality and post-fledging predation levels, and availability and adequacy of nesting and brood-rearing habitat may provide more insight into why population levels of hooded mergansers appear to be so low on the study area and/or why occupancy levels of nest boxes on the study area are low. Such findings might also explain the large distances moved by hooded mergansers. The management and maintenance of beaver ponds and shrub swamps should be encouraged to assist the hooded merganser population of HWF. While such areas do not appear to need to be very large, their proper juxtaposition and interspersion should be evaluated and incorporated into the management scheme.