Food

A caterpillar found on vegetation during one of the surveys for warbler food items (photo by S. Sillett).

Researchers also conduct insect surveys to determine the amount of food available to warblers during the breeding season. Black-throated Blue Warblers primarily forage by gleaning insects off leaves. They have a particular preference for moth and butterfly larvae (also known as caterpillars), energy-rich food items that they eat themselves and also feed to their young. Every two weeks, researchers examine a few hundred leaves of a variety of plant species throughout the study area, carefully looking for and counting the number of caterpillars that they see. Those data are then used to determine the relative abundance of caterpillars, both across space and through time.