Seven species of rosy-finch occur in North America and Asia, and all have alpine or tundra affinities. Of the 3 North American species, the Black Rosy-Finch is much the darkest in color (a very dark brown that appears black in the bright alpine environment), and it holds the middle position geographically between the Gray-crowned Rosy-Finch (L. tephrocotis) to the north and west and the Brown-capped Rosy-Finch (L. australis) to the south and east. These three North American species were combined and merged with one of the Asian species (Leucosticte arctoa) from 1983–1993, but justification for this was judged insufficient (Am. Ornithol. Union American Ornithologists' Union 1983, American Ornithologists' Union 1993), and is contradicted by genetic, biochemical, and morphological evidence (Johnson 1972d, Sibley and Monroe 1990, Zink et al. 1995). Consequently, they are again considered as 3 distinct species.
Black Rosy-Finches breed above treeline, nesting mostly in cracks and holes in cliffs, often overlooking snowfields and glaciers in the highest mountain ranges. They are most often seen feeding on insects and seeds on snow banks, and along their muddy, melting borders, where old food items are freshly uncovered, new items are deposited by the melting snow, and seeds are germinating. In addition to crops, rosy-finches possess special paired sacs beneath the floor of the mouth, found only in one other North American genus (Pinicola), which allow parents to carry extra food with each trip to the young. The increased payload makes longer flights profitable and allows parents to search for food over a wider area, as far as 4 kilometers from the nest in this sometimes barren environment.
In most locations, this is the species that nests at the highest elevation. The alpine season is short, so breeding activity must begin as early as resources allow in order to complete the breeding cycle before extreme weather drives individuals down into the lowlands. Thus, the Black Rosy-Finch arrives in the alpine in April, when the ground is still deeply covered with snow, and it remains there poised to take advantage of the first break in conditions. The breeding biology of the species is somewhat unusual in that a male primarily defends a floating territory around his mate, rather than around a fixed piece of alpine real estate. As a result, males constantly chase other males that approach their mates too closely, and females are most readily located by looking near the locus of all the fighting. These behaviors are thought to result from a skewed sex ratio with females in short supply, but the questions of mating system, sex ratio, and the possible role of unmated males deserve further study.
In winter, this finch is driven down to high deserts, parks, and valleys that are often thinly or periodically covered by snow, where they forage on patches of bare ground and at feeders and cattle troughs or along freshly plowed highways, where they move, leap-frog fashion, in large flocks. But they also commute upward on days when the weather is fair to feed where high winds have blown the tundra free of snow. At night, they roost in large communal roosts in caves, mine shafts, on rafters of barns, and in clusters of old Cliff Swal-low (Petrochelidon pyrrhonota) nests.
Black Rosy-Finches are among the least studied of North American birds because of the inaccessibility of their alpine habitat generally and their nest sites on cliffs in particular. Reflecting this, actual nests have been reached by only 3 workers (Miller 1925b; French 1959b; Johnson 1965c, this manuscript), and only a few studies have focused on the species. The latter include French's landmark work (French 1954b, French 1959a, French 1959b, French 1968) on its breeding biology, distribution, taxonomy, and winter roosts; King and Wales (King and Wales 1964, King and Wales 1965) on wintering populations in Utah; and Johnson's studies (Johnson 1965c, Johnson 1966c, Johnson 1972d, Johnson 1975c, Johnson 1977b, this manuscript) on systematics, and breeding biology, distribution, and behavior. This manuscript draws heavily on these sources and also attempts to bring together small but valuable bits of information from the widest range of other sources possible in order to flesh out what is known about the species. As will be seen, while much is known, nearly every aspect of the biology of the species deserves further study.