Second North American Sea Duck Conference - Patuxent Wildlife ...

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
¹Ducks 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 North 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