Introduction

The Indigo Bunting, one of our best known songbirds, is a small migratory species that breeds in eastern North America and winters primarily in southern Florida, Mexico and Central America, and on islands in the Gulf of Mexico. It sings through the late spring and summer in brushy and weedy places. Older males are bright blue in plumage, the head somewhat more purplish blue, while females are brown often with a touch of blue on the shoulders, rump and tail; first-year males range from blue to a little blue with mostly brown and white plumage.

Indigo Buntings live in shrubby areas and weedy fields. Their colorful appearance and cheerful songs are good reasons to fallow old fields and to spare (not spray) herbicides along railways and roads. "The bird is a constant singer from the time it arrives until the second brood is out of the nest, and it sings volubly during the hottest part of the day, usually selecting the top of some small tree and repeating its song many times before it seeks another perch" (Barrow 1912: 536). First-year Indigo Buntings learn their song during their first breeding season, in social interactions with other buntings, and they do not sing the father's song. Neighboring males share their songs in local song dialects or song neighborhoods. These distinct song themes persist as long as 20 years (ten or so bunting generations) even as the song themes are modified when new singers add new twists to the song tradition from generation to generation. Males sometimes allow more than one mate to nest on their territory , and females often mate with more than one male in a nesting attempt.

Buntings migrate 2,000 km or so each way between their breeding grounds and their winter sites in the norther Neotropical region. They sometimes return to breed in their natal area, although most birds settle at least a few kilometers away. Even though individuals of this species are morphologically similar across eastern North America, breeding populations retain their east-west spatial relationships when they migrate and winter in the Neotropics—birds that breed in the eastern part of their breeding range winter in the eastern part of the winter range. On average, buntings have low survival, although individual birds live as long as 11 years.

Key studies of Indigo Buntings have been completed in southern Michigan, near Niles and around the E.S. George Reserve at the University of Michigan. At the George Reserve, George Sutton studied breeding behavior and development of juvenal plumage (Sutton 1935, 1959), Steve Emlin tested behavior in migration (Emlen 1967a, b), Bill Thompson and Jake Rice (Rice and Thompson 1968, Thompson 1970, 1972; Thompson and Rice 1970) recorded songs and calls in the 1960s, and Bob Payne, colleagues and students worked with song, dispersal, demography and cowbird parasitism of color-marked buntings from 1977 to 1994(Payne 1981, 1982, 1989, 1991, 1996; Payne et al. 1981, 1987, 1988, 1996, 1983a, b; Payne and Payne 1990, 1993a, b, 1997, 1998). A second color-marked population was studied from 1977 to 1989 at Niles (references just above), and Dave Westneat (1986, 1987a, b, 1998a, b) also completed three years there in behavior and molecular studies of extra-pair matings.

The other main study region for buntings has been the northern Great Plains in work with song and interspecific hybridization (Sibley and Short 1959, Emlen et al. 1975, Kroodsma 1975, Baker 1991, 1994, 1996; Baker and Baker 1990, Baker and Johnson 1998, Baker and Boylan 1999).