Connecting the trophic dots : responses of an aquatic bird species to variable abundance of macroinvertebrates in northern boreal wetlands /

Includes bibliographical references (pages 14-17).

To evaluate variation in abundance of boreal
wetland macroinvertebrates and test for effects of this
variation on the diet and habitat use of a bird species that
consumes aquatic invertebrates (lesser scaup, Aythya
affinis), we collected macroinvertebrates and birds and
conducted bird surveys (June–August) at two wetland
complexes in northwestern Canada and assessed diet
composition using an isotopic approach. At both study
areas, for macroinvertebrate taxa reported to be key prey
items for scaup, biomass varied intra-seasonally and
annually, but patterns differed among taxa and between
areas.Macroinvertebrate biomass varied strongly across
wetlands within study areas, and isotopic mixing models
indicated that local heterogeneity in macroinvertebrate
biomass was reflected in duckling diets, which also
varied across wetlands, indicating a generalist foraging
strategy for this species.Wetland habitats used by broodrearing
female scaup had greater amphipod and gastropod
biomasses. Our results show that boreal wetland
macroinvertebrate abundances vary considerably across
coarse and fine spatial scales. Female scaup and their
ducklings appear well adapted to exploit this dynamic
food resource, but overall productivity of scaup may
depend on the abundances of certain taxa, suggesting
that conservation efforts should focus on maintaining
abundant populations of key wetland invertebrates.