Range, Wildlife and Fisheries Management
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Nest Site Selection and Brood Habitat
Use by Greater Scaup on the Saint John
River, New Brunswick
by W. Andrew Smith, Warren B. Ballard, Patrick Kehoe, and Tim Dilworth
In North America greater scaup traditionally breed in the arctic and northern boreal forest regions of Alaska and the Canadian territories. Grassy Island, located in southern New Brunswick, is the southern most breeding area for scaup in North America. Scaup nests on the island increased from 21 in 1986 to 148 in 1989, and decreased to 104 in 1995. Grassy Island was grazed by about 15 cattle annually until 1988. Since that time the plant community has been changed by invading tall grasses, forbs, trees, shrubs, and purple loosestrife. Concerns have been raised that the vegetation changes may be affecting scaup nesting on Grassy Island.
Our objectives for this study were to examine how habitat changes on Grassy Island have influenced the nesting biology of greater scaup, to examine the relationships between gull colonies and greater scaup nest location, and to examine the effects of inclement weather and flooding on greater scaup nesting success and duckling survival.
Field work for this study was conducted during 1995 and 1996. Early spring flooding, inclement weather, and plant succession all affected nesting success. We found that the presence of gulls had a greater influence on nest site selection by greater scaup than did habitat characteristics or site tenacity. Apparently gulls acted as a stimulus for greater scaup and scaup used sub-optimal or more open habitats when nesting with gulls. Scaup which nested away from gull colonies had greater nest failure due to predation than did scaup which nested in association with gulls. Advancing plant succession has reduced the amount of suitable scaup nesting habitat on Grassy Island. We recommended that limited grazing by cattle, or controlled burning be instituted to increase scaup nesting habitat.
Nasal tags were used to identify individual greater scaup for nesting studies on Grassy Island, New Brunswick.