Canvasback Food Density in the Mississippi River Delta, Louisiana: Habitat and Temporal Differences

Wildlife managers have been creating deltaic splays in the Mississippi River Delta to promote marsh regeneration, but little is known of the quality of splays as waterfowl foraging habitat. Consequently, we compared densities of important canvasback (Aythya valisineria) foods in splays and open-water ponds during winter 1990- 91. Biomass (g/m2) of grassy arrowhead (Sagittaria graminea) tubers differed between splay mudflats and ponds, but the difference was not consistent between months. In November 1990, splay mudflats (mean ± SE = 123.7 ± 2.9) supported a greater biomass of tubers than did ponds (43.8 ± 2.9). In March 1991, tuber biomass was similar between habitats (splays = 12.6 ± 2.9, ponds = 23.7 ± 2.9) because of a marked decrease in tubers in splay mudflats between sampling periods. American bulrush (Scirpus americanus) rhizomes were not present in samples from ponds. Mean ± SE rhizome biomass (g/m2) in splay mudflats declined from 63.4 ± 14.2 in November 1990 to 20.0 ± 14.2 in March 1991. Mudflats accounted for the greatest percentage of the total area of splays (mean ± SE = 66.4% ± 4.6), followed by high banks (6.7% ± 2.6) and channels (5.4% ± 0.8). Splay mudflats supported more extensive above ground patches of the 2 plant species (mean percent coverage ± SE = 70.6% ± 14.7) than did channels (30.2% ± 9.1), high banks (6.3% ± 2.1), or ponds (9.6% ± 3.4). Our results indicate that splays are superior foraging habitats as compared to ponds, and continued construction of splays should improve the suitability of the Mississippi River Delta for wintering canvasbacks.

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ID
25174