Abstract
The abundance and distribution of lesser scaup (Aythya affinis) may be influenced by the availability of amphipod crustaceans, since these invertebrates represent an important food source, particularly for immature birds. Another important factor may be degradation of habitat, since seaup nest in wetland margins and adjacent upland habitats. The objective of this study was to evaluate the relative importance of amphipods, wetland features such as area and water depth, and indices of margin/upland habitat, on the distribution and abundance of scaup. A subsample of 108 oligosaline wetlands was chosen on twelve sites located in three eco-regions of southern Saskatchewan, Canada. Data were gathered during 1995 on relative amphipod abundance, wetland area, fall water depth, upland nesting habitat type, wetland margin impacts, and spring numbers of lesser scaup. Scaup use of wetlands was significantly affected by the availability of amphipods, wetland margin impacts, and wetland area. Controlling for the effect of area showed that scaup were most common on ponds with abundant amphipods and minimal margin impacts. In the southernmost mixed grassland eco-region, scaup were affected by amphipod availability only, whereas in the moist mixed grassland and parkland eco-regions, results indicated that both margin impact and amphipod availability were significant factors. Results are consistent with hypotheses that decreases in scaup numbers since the mid-1980s may be due to (1) loss, resulting from both human and climatic factors, of natural wetlands capable of supporting rich amphipod populations and (2) continuing agricultural encroachment on remaining wetlands.
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Lindeman, D.H., Clark, R.G. Amphipods, land-use impacts, and lesser scaup (Aythya affinis) distribution in Saskatchewan wetlands. Wetlands 19, 627–638 (1999). https://doi.org/10.1007/BF03161700
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DOI: https://doi.org/10.1007/BF03161700