SECOND NORTH AMERICAN SEA DUCK CONFERENCE A COMPARATIVE ASSESSMENT OF FOOD USE AND AVAILABILITY BY SCAUP AND SCOTERS IN THE LOWER MACKENZIE WATERSHED, NORTHWEST TERRITORIES, CANADA Lisette Ross¹, Jean-Michel DeVink², Stuart Slattery¹, and Llwellyn Armstrong¹ ¹<strong>Duck</strong>s Unlimited Canada, Institute for Wetland and Waterfowl Research, Box 1160, Stonewall, Manitoba, R0C 2Z0; jean-michel.devink@ec.gc.ca ²Department of Biology, 112 Science Place, University of Saskatchewan, Saskatoon, Saskatchewan, S7N 5E2 Continental populations of scaup (Aythya spp.) and scoters (Melanitta spp.) have apparently declined 41% and 58% respectively in the past 25 years. Scoters have decreased from 1.8 million to 700,000, while scaup populations dropped an average of 150,000 birds per year. While scaup and scoters winter in different locations, retrospective analyses examining correlations between the two taxa suggest that they share limiting factors in the <strong>North</strong> West Territories (NWT) of Canada, their core breeding area. Declines here approach 70%. Timing of food availability is crucially important to arctic nesting birds with highly constrained breeding seasons; a shift in this timing could result in a lack of resources for successful reproduction. The objectives of this study were to assess scaup and scoter diet selection, compare interspecific dietary preferences, and determine how food availability affects scaup and scoter distribution during nesting and brood rearing. In 2003 we examined invertebrate availability and hydrology of 31 wetlands in the Lower Mackenzie Watershed (LMW), NWT, during prenesting and brood rearing periods; and, during prenesting in 2004, we collected and preserved the ingesta of 46 lesser scaup and 50 white-winged scoters from nearby wetlands. Initial analyses indicate that invertebrate biomass and wetland chemistry affected both brood use and nesting locations. We will compare the ingesta from the collected birds to the diversity, abundance and biomass of invertebrates available in these wetlands to assess how diet selection contributed to this relationship. This research will help us to identify the importance of food availability on breeding habitat selection. Since wetland invertebrates are closely linked to water temperature, ice-free days, and photoperiod, climate change in this region has the potential to strongly influence aquatic invertebrate populations and the waterfowl that depend on them. 58 ANNAPOLIS, MARYLAND, USA NOV. 7-11, 2005
SECOND NORTH AMERICAN SEA DUCK CONFERENCE ABSTRACTS FOR BREEDING BIOLOGY PRESENTATIONS NOV. 7-11, 2005 ANNAPOLIS, MARYLAND, USA 59