Waterbird nest density and nest survival in rice fields of southwestern Louisiana

Rice fields in southwestern Louisiana provide breeding habitat for several waterbird species; however, little is known about nest density, nest survival and the importance of landscape context of rice fields in determining breeding activity. In 2004, 42 rice fields were searched for nests, and 40 were searched in 2005. Land uses surrounding rice fields, including irrigation canals, trees, crawfish ponds, rice, fallow and soybean fields, were examined to determine influence on nest density and survival. Nest densities were 13.5-16.0 nests/km² for Purple Gallinules (Porphyrio martinica), 3.0-13.7 nests/km² for Fulvous Whistling Ducks (Dendrocygna bicolor), 2.6-2.8 nests/km² for Common Moorhens (Gallinula chloropus), 0.3-0.92 nests/km² for Least Bitterns (Ixobrychus exilisi) and 0-0.6 nests/km² for Mottled Ducks (Anas fulvigula). Nest survival was 52-79% for Purple Gallinules and 39-43% for Fulvous Whistling Ducks. Apparent nest success of Common Moorhens was 73-75%, 83% for Least Bitterns and 33% for Mottled Ducks. Purple Gallinule and Common Moorhen nest densities were highest in fields with a larger proportion of irrigation canals surrounding rice fields. Purple Gallinule nest densities were greater in fields devoid of trees and landscapes dominated by rice fields and pasture, rather than landscapes containing soybean fields and residential areas. Fulvous Whistling Duck nest densities were higher in agriculturally-dominated landscapes with few trees.