Introduction

The Ruby-throated Hummingbird, eastern North America’s only species of breeding hummingbird, is a familiar summer inhabitant of woodlands, parks, and gardens from central Canada to the Gulf Coast. In geographic area, this species occupies the largest breeding range of any North American hummingbird. In the United States, the western boundary of its breeding range ends along a remarkably straight north-south line, just east of the 100th meridian. This distribution, as well as that in west-central Canada, conforms closely to the range of eastern deciduous and mixed forests (Bertin 1982a).

Adult Ruby-throated Hummingbirds have a mass of only 3.5 grams on average. Despite their tiny size, many of these birds fly nonstop across the Gulf of Mexico during fall and spring migration, a round-trip of more than 1,600 km. To accomplish this, individuals often double their body mass by fattening on nectar and insects prior to departure. In general, however, migratory routes of this species remain poorly documented, and some proportion of the population may follow a coastal route south during the fall.