Foraging Microhabitat Selection by Wading Birds in a Tidal Estuary, with Implications for Conservation

The importance of the lower Rahway River, New Jersey, to wading birds was investigated, and foraging patterns and interspecific differences in wading bird microhabitat use are described. Foraging decisions by wading birds are complex and occur at several levels. In order to examine foraging decisions at the habitat and microhabitat levels, 79 censuses were conducted by boat along a 5-km tidal section of this river in 1988, 1998, 1999, and 2002. The locations of 1,148 birds were recorded on maps, and patterns of microhabitat use were determined. Overall, year, date, and tide level were important predictors for the numbers of wading birds that were recorded. However, each species responded to a different combination of variables: for Great Egret it was year and date; for Snowy Egret date and tide level; and for Glossy Ibis year, date, and tide level. Tide flow direction was not important for any species. For all three species, spatial distributions long the river were clumped rather than uniform, which were associated with physical characteristics along this section of the river. All three species used the mouths of narrow tidal creeks more frequently than expected, but species differed in the use of mudflats and areas of slow-moving water. There was little overlap among species in spatial distribution along the river, but the overall use of microhabitats was broadly similar. This study suggests that the lower Rahway River estuary in New Jersey is valuable to local wildlife and should be considered in future development plans.