Recent Change in the Winter Distribution of Rufous Hummingbirds

Abstract

Rufous Hummingbirds (Selasphorus rufus) breed in northwestern North America (Idaho and Oregon north to Alaska) and winter primarily in northwestern and central Mexico (Calder 1993). The species was first recorded east of the Mississippi River during winter in Charleston, South Carolina on 18 December 1909 (Conway and Drennan 1979). After this initial detection, records of Rufous Hummingbirds east of the Mississippi River remained sporadic until the 1970s, when steadily increasing numbers were reported in the fall and winter along the Gulf Coast (Conway and Drennan 1979). This increase has continued to the present, and Rufous Hummingbirds are now considered regular along the Gulf Coast in winter from Texas to Florida (Newfield 1992, Calder 1993). Here, we document the rate and extent of increase in Rufous Hummingbirds wintering in the southeastern United States and discuss hypotheses that might explain this recent increase in numbers. Documenting the increase.-Conway and Drennan (1979) summarized sight records of Rufous Hummingbirds east of the Mississippi River through the 1970s. We used their summary to plot the number of Rufous Hummingbirds reported in winter east of the Mississippi River by decade and found a relatively steady increase through the first seven decades of this century (Fig. 1). Beginning in the fall of 1988, RRS and MBS began studying wintering hummingbirds in Alabama, Georgia, Florida, Mississippi, and Tennessee. They compiled reports of wintering hummingbirds in these states and, when possible, captured and banded the birds. This work has been conducted with relatively constant effort over an eight-year period, during which the number of Rufous Hummingbirds banded and sighted has increased rapidly (Fig. 2). When these recently compiled sight records are compared with sight records compiled by Conway and Drennan (1979), the magnitude of the increase in wintering Rufous Hummingbirds in the Southeast is easy to discern. In the 70 years between 1909 and 1979, 68 Rufous Hummingbirds were sighted east of the Mississippi (Fig. 1). In the six winters from 199091 to 1995-96 in just the five-state region covered by the wintering hummingbird study, 1,643 Selasphorus hummingbirds were reported (Fig. 2). Between 7