Use of public information versus location cues in habitat selection by black-throated blue warblers

Uncovering the types of information used by animals in habitat selection is a central question in ecology. Most animals are under strong selection pressure to make optimal breeding habitat choices. Recent research indicates that some animals gather environmental information by observing the reproductive success of conspecifics (“public information” [PI]). Alternatively, animals may derive information by simply observing the location of another animal (“location cues”). PI is more time-consuming to collect, but provides greater detail on habitat quality than location cues. Location cues are more open to error, because an onlooker has no means of gauging the reliability of the observed animal’s choices. Both of these forms of information could explain clustering patterns observed in breeding sites of forest birds. We conducted a controlled manipulative experiment to determine whether black-throated blue warblers (Dendroica caerulescens) use either PI or location cues in habitat selection. During and after the breeding season we provided artificial PI (decoys of fledglings and playback fledgling calls) and location cues (adult song) across a gradient in forest succession in White Mountains, New Hampshire, USA. Both experimental treatments attracted adult and fledgling warblers in the year of the experiment. Individuals often remained at treatment sites for up to 10 days following trials. In the following breeding season, immigration to PI sites was greater than both the location cues sites and controls.