Distribution and Habitat Requirements of Scoters in the Mackenzie Delta Region

Abstract

Combined white-winged and surf scoter populations have experienced apparent long-term declines across the continent, and those populations in the boreal forest of northern Alberta, British Columbia, and the Northwest Territories (NT) may have declined by as much as 75% in the past 50 years .... Reasons for the decline are not well understood because so little previous research has been conducted on scoters, particularly in northern portions of their breeding range, and to my knowledge none has attempted to determine why scoters use specific areas or wetlands, but do not use others. This study addresses this last deficiency by examining how specific wetland characteristics affect the abundance, distribution, and productivity of white-winged and surf scoters in part of their core breeding range near Inuvik, NT. In particular, I designed my research to look for evidence of habitat selection by these species. Do female scoters select wetlands that are more productive and have a greater abundance of key food items, or are better suited to providing physical protection for ducklings? Are these types of preferred wetlands widely distributed and available for use by scoters, or are they not very abundant- perhaps limiting scoter productivity? ... My study area is located about 75 km south of Inuvik, Northwest Territories, and encompasses approximately 6200 km² of the southern Mackenzie Delta (Delta) and surrounding upland area .... Study plots were randomly selected from each region: 16 from the Delta and 15 from the upland habitat in 2001, and 11 Delta and 18 upland plots in 2002. Overall, 13 upland plots had been burned in a 1999 forest fire. ... To assess annual variation in scoter abundance and wetland occupancy, in 2002 I revisited 10 of the 31 plots surveyed in 2001 (five in each region), as well as visiting 29 new plots. ... In both years, wetlands were surveyed for pairs in mid to late June and for broods in late July or early August. Survey data were used to assign each wetland to a "use" category (separately for each species): (1) used by pairs, (2) used by broods, or (3) not used by either species. ... Before I can determine how specific wetland characteristics affect abundance, distribution, and productivity of scoters, I must first attempt to identify patterns in the distribution of scoter pairs and broods. ... My results to date indicate where scoters are found during the breeding and brood-rearing periods of the summer. Further analyses of spatial and habitat data from both years must be conducted to contrast characteristics and occupancy of burned and unburned areas and to evaluate whether or not a habitat selection pattern exists. I hope the analyses will allow me to determine what habitat characteristics scoters require to breed successfully in this part of their range. This information, used in conjunction with that for other species, could be used to help mitigate future impacts of proposed developments. It will also provide a baseline from which causes of future changes in scoter abundance and distribution could be determined more easily.