David Haskell created artificial nests with clay eggs and placed them on the ground beside a tape recorder that played the begging calls of either tree-nesting or of ground-nesting warblers.

David Haskell 制作了一些盛有泥蛋的人造鸟巢并把它们放在地面上，旁边有一个录音机，播放着树莺或地面莺的的乞食叫声。