Introduction

The Lesser Goldfinch is a small, social, seed-eating songbird that inhabits a wide variety of habitats of the western United States from Oregon east into Colorado and Texas, and south to Mexico. South of the United States, it is widespread through Mexico and Central America, and its range extends into northern and western South America. In the United States, it is common in California and central Texas, the two areas of highest population density, but less common and more locally distributed in other regions. This species is most commonly found in small groups in open country with scattered trees, along western range foothills, and frequently in agricultural lands. Like many cardueline finches, it is often nomadic and sporadic in occurrence.

In general, this species is less well known than its congener the American Goldfinch (Carduelis tristis), being less widely distributed in the United States, less abundant, and less studied. Much information available for the species is general and anecdotal and is often assumed to be similar to that known for the American Goldfinch. Like the American Goldfinch, the Lesser Goldfinch breeds in loosely colonial groups, defending territories only near its nest, and it seems to be monogamous during the breeding season, with the male feeding the female on the nest throughout incubation. In winter it congregates in foraging flocks, often with other cardueline finches. Throughout the year it feeds almost exclusively on seeds, mostly of composites. Its adaptability to a wide range of foods and habitats, including those modified by human activities, appears to have protected it from widespread population decreases during the recent past.

Notable characteristics of this species are its incorporation of other species’ songs into the male song repertoire, and its geographic plumage polymorphism: Western males (C. p. hesperophila) have green backs, and eastern forms (C. p. psaltria) have black backs. These 2 subspecies also exhibit different molt and breeding phenologies.

The species seems to have received little scientific and almost no recent attention: A bibliographic survey revealed about 60 references, most in field guides or general avian surveys. A few were primary research papers dealing with Lesser Goldfinch biology, including observations of a nest (Chambers 1915), a study of maintenance behaviors (Coutlee 1968b), comparative studies of breeding biology (Coutlee 1966, 1968a) and vocalizations (Coutlee 1971) of Lesser and Lawrence’s (Carduelis lawrencei) goldfinches, analysis of vocal mimicry (Goldwasser 1987), and inclusion in a study of genetic relationships of North American cardueline finches (Marten and Johnson 1986). Linsdale’s (1957) detailed study of diet, ecology, and breeding of goldfinch species at Hastings Natural History Reservation in Monterey Co., CA, provided the information in A. C. Bent’s life history series (Linsdale 1968), as well as much of what is reported in this account for those topics. Gross (1968) summarized traits of the eastern sub-species (psaltria) in A. C. Bent’s life history series.