ABSTRACT
Prairie warblers are common in disturbed habitats of the eastern US They arrive on the breeding grounds in April and leave in August. Soon after their arrival, males establish exclusive territories which they defend for the entire breeding season. Unlike that of many other passerine birds, the utilized area of a Prairie Warbler territory does not appear to change in size during the breeding season. Because a large fraction of the males are polygynous, the following method accurately estimates only male densities; female and nest density may be very different and will also vary considerably during the breeding season. If necessary males can be lured into a net by playing a recorded song through a speaker placed behind it. Males are usually not affected by an observer following from 3 to 4 m away. At the end of the observation, plot the male's activity space on the grid map.
