Introduction

Each spring, the forests of New Hampshire come alive with the arrival of migratory birds. Many migrate from wintering areas in the tropics to take advantage of the abundant insects and the long summer days of northern areas, which are beneficial when raising young. This annual spring migration to northern regions is a pattern that has repeated itself since the last Ice Age, but it is one that has led to considerable conservation concern in recent years.

Migratory birds have been declining in abundance across North America, and researchers are scrambling to figure out why. Is it because of changes on the breeding grounds? Or changes where the birds winter? Or along their migratory pathways? Is it habitat loss, changing weather patterns, or some other factor? One of the ways to get at those questions is to understand what factors in the environment influence how well migratory birds survive and how many young they produce.

At the Hubbard Brook Experimental Forest in central New Hampshire, researchers have been studying birds since 1969 and have particularly detailed information about the breeding biology of a species called the Black-throated Blue Warbler. Here, we will explore what has been learned over the course of long-term research on this migratory bird, asking questions like:

- How do you study birds?

- What factors influence the breeding success of warblers?

- How might changes in climate impact this species?