One of the most notable ornithological events of the twentieth century in North America has been the spread of the House Finch throughout the eastern portion of the continent from a small number of birds liberated on Long Island, New York in 1940. The House Finch is now a common backyard bird throughout most of the contiguous United States and southern Canada. In its native west, this species occupies a wide range of open or semi-open habitats from undisturbed desert to highly urbanized areas. In the east, it is rarely found far from urban or suburban areas. Throughout its range, its fondness for feeding stations and for nesting conspicuously around buildings makes the House Finch among North America's most familiar birds.
One of the most striking features of House Finches is their extreme variation in male plumage coloration. In all populations males vary in color from pale yellow to bright red; in addition, the average coloration of males varies substantially among populations. Most notable is the virtual absence of red males on some of the Hawaiian Islands, where the species has been introduced. Males derive their yellow/orange/red coloration from carotenoid pigments in their food, and variation in the expression of male plumage coloration both within and among populations reflects variation in dietary access to carntenoid pigments during molt. Female House Finches prefer to mate with the reddest male available to them, and by choosing to mate with brightly colored males they gain resource benefits during nesting.
Several distinctive populations exist within the native range of the House Finch, but the evolutionary relationships among these groups needs further study. Many populations are poorly described and plasticity in plumage coloration, a character often used to diagnose subspecies, has further muddled the taxonomic status of many populations.
House Finches in California, Hawaii, and eastern North America have been reasonably well studied, but little is known about the endemic Mexican and island populations. This is an abundant bird; estimates suggest between 267,720,000 and 1,440,720,000 individual House Finches for the continental U.S. and Canada.
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