Comparison of line transects and point counts for monitoring spring migration in forested wetlands

We compared the efficacy of 400-m line transects and sets of three point co unts at detecting avian richness and abundance in bottomland hardwood fores ts and intensively managed cottonwood (Populus deltoides) plantations withi n the Mississippi Alluvial Valley. We detected more species and more indivi duals on line transects than on three point counts during 218 paired survey s conducted between 24 March and 3 June, 1996 and 1997. Line transects also yielded more birds per unit of time, even though point counts yielded high er estimates of relative bird density. In structurally more-complex bottoml and hardwood forests, we detected more species and individuals on line tran sects, but in more-open cottonwood plantations, transects surpassed point c ounts only at detecting species within 50 m of the observer. Species richne ss and total abundance of Nearctic-Neotropical migrants and temperate migra nts were greater on line transects within bottomland hardwood forests. With in cottonwood plantations, however, only species richness of Nearctic-Neotr opical migrants and total abundance of temperate migrants were greater on l ine transects. Because we compared survey techniques using the same observe r, within the same forest stand on a given day, we assumed that the techniq ue yielding greater estimates of avian species richness and total abundance per unit of effort is superior. Thus, for monitoring migration within hard wood forests of the Mississippi Alluvial Valley, we recommend using line tr ansects instead of point counts.