SIGNIFICANCE OF INVERTEBRATE ABUNDANCE TO DABBLING DUCK BROOD USE OF CREATED WETLANDS

We investigated factors influencing dabbling duck (Anas spp.) brood de nsities on 9 created wetlands, arranged in 4 clusters on the National Elk Refuge in western Wyoming. Because dabblers are limited by the dep th they can reach while up-ending, and created wetlands were between 1 .5-2.5 m deep, we examined the significance of invertebrate density in the top 25 cm of the water column and in the entire water column wher e brood use occurs. Total invertebrate, nekton, and zooplankton densit y in the entire water column measured in 1992 accounted for between 59 %, 61%, and 73%, respectively, (P < 0.05) of the variation in brood de nsity among wetlands that year. No variable measured in the top 25 cm of the water column accounted for variation in brood densities on wetl ands. We suggest that vertical migrations in the water column make mos t invertebrates accessible to dabbler hens and broods.