THE IMPACT OF SHOREBIRD FORAGING ON MACROINVERTEBRATES IN THE LOWER MISSISSIPPI 
ALLUVIAL VALLEY

Darren W. Mitchell and Jack W. Grubaugh
The University of Memphis, Department of Biology, Memphis, TN 38152

Studies of macroinvertebrate communities of along the eastern coast of North 
America indicate migrating shorebirds significantly impact benthic community 
composition. However, studies from the upper Midwest indicate no similar impact 
by shorebirds on those benthic communities. No such studies have been conducted 
in the Lower Mississippi Alluvial Valley (LMAV) portion of the flyway. Using an 
exclosure study design, we quantitatively sampled macroinvertebrate abundance 
and biomass in shorebird management areas at Bald Knob (AR) National Wildlife 
Refuge during the peak of the fall migration. Aquatic worms (Oligochaeta) 
dominated benthic abundance and biomass inside and outside of the exclosures, 
which resulted in a high community similarity between exclosure and open sites 
(% similarity = 88). Chironomidae (Diptera) abundance was significantly greater 
inside of the exclosures (p= 0.03), but total macroinvertebrate abundance did 
not differ significantly between treatments (p = 0.34). Likewise, chironomid 
biomass was significantly greater in the exclosures (p = 0.03), as was overall 
benthic biomass (p = 0.05). These results indicate that foraging shorebirds do 
have some effect on benthic community composition and suggest that shorebirds 
may be selectively feeding on chironomid larvae in managed habitats of the LMAV.

Keywords: biomass, exclosure, Lower Mississippi Alluvial Valley, 
macroinvertebrates, shorebirds