|SREL Reprint #1094|
Effect of Diving Ducks on Benthic Food Resources during Winter in South Carolina
M. Smith, Larry D. Vangilder, Richard T. Hoppe, Stephen J. Morreale and
Recently, increased attention has been focused on
the role of the winter period in limiting waterfowl populations (Anderson &
Batt 1983). Many current studies
suggest that winter food resources may be a limiting factor (Phersson 1976;
Alexander & Hair 1979; Saylor & Afto 1981) for diving ducks.
Benthic food resources may decline over winter and competitive
interactions among waterfowl, and between waterfowl and fish, have also been
suggested as causes for food limitation (Nilsson 1969; Thompson 1973; Pehrsson
1976). Although recent studies have demonstrated that herbivorous waterfowl may
reduce wetland macrophyte production (Smith & Odum 1981; Smith & Kadlec
1985) few studies have directly tested the hypothesis that diving ducks affect
their winter invertebrate food resources.
Studies examining the impacts of diving ducks on
benthic invertebrates have been complicated by the natural decline in
invertebrates during winter and the difficulty of determining what portion of
that decline, if any, may have been due to predation by waterfowl.
Also, many studies have indirectly extrapolated from estimated feeding
rates to total food consumption. In
this study, our first objective was to estimate the direct impact of waterfowl
predation on benthic invertebrates using enclosures.
Secondly, we investigated whether deep waters contained richer food
resources, when compared with shallow waters.
SREL Reprint #1094
Smith, L.M., L.D. Vangilder, R.T. Hoppe, S.J. Morreale,
and I.L. Brisbin Jr. 1986. Effect of diving ducks on benthic food
resources during winter in South Carolina, USA. Wildfowl