Predators

A Red Squirrel, one of the major predators of Black-throated Blue Warbler nests at Hubbard Brook (photo by S. Lemelin).

While monitoring the reproductive activities of Black-throated Blue Warblers, the researchers also collect data on predator abundance, food availability, and warbler density. For instance, throughout the breeding season predator surveys are conducted in the core area of warbler territories, often near nests. Researchers stand at particular points and spend 5 minutes continuously watching for potential nest predators, noting their location on a data sheet. At Hubbard Brook, the most common nest predators seem to be chipmunks and red squirrels, although there are other predators like jays and hawks that warbler parents also have to contend with. All of these are noted in the surveys, and the data are ultimately used to determine the abundance of different kinds of predators within a warbler's territory, as well as across the study area as a whole.