Birds
Finch
Fringillidae · also called finches, true finch
A finch is a bird built around a bill. Short, deep, and conical, it is a seed press: it turns a seed on edge, grips it in a grooved palate, and cracks the husk with a single bite. From that one tool the true finches have made a living everywhere from Arctic conifer forests to the high Andes — and one branch, marooned in Hawaii, turned into dozens of species doing dozens of different jobs.
Overview
True finches are the family Fringillidae, around 230 species, native to the Americas, Europe, Africa, and Asia. They are small songbirds with a stout conical bill, a bounding flight, and the habit of feeding their young on regurgitated seed paste. The family holds the chaffinches, the goldfinches, siskins, linnets, redpolls, and crossbills, the bullfinches and hawfinches, the canary, and — surprisingly — the Hawaiian honeycreepers. Many other birds are called finches but belong to other families.
The bill as a tool
Bill shape ranges from the fine points of goldfinches, which work thistle and teasel heads, to the massive hawfinch bill that can split a cherry stone. In the crossbills the tips cross over, letting the bird lever apart the scales of a closed spruce or pine cone and lift out the seed long before other birds can reach it.
The mine canary
The pet canary was bred from a wild island finch for song and colour. Because a small bird breathes more air for its size than a person, a caged canary showed distress from carbon monoxide in a coal mine while the gas was still low enough for miners to escape — a practice that continued in Britain until 1986.
Status
Finches as a family are Not Evaluated. Many, like the chaffinch and house finch, are abundant, but the Hawaiian honeycreepers are among the most threatened birds on Earth — many already extinct, most survivors Critically Endangered from introduced mosquitoes and avian malaria — and some continental finches are declining from lost field margins and cage-bird trapping.
Finch: common questions
What makes a bird a true finch?
Membership of the family Fringillidae. True finches are small songbirds with a stout, conical seed-cracking bill, nine visible primary feathers in the wing, a bounding flight, and a particular pattern of feeding their young by regurgitating a paste of seeds rather than delivering whole insects. The family includes the chaffinches and bramblings, the cardueline finches such as goldfinches, siskins, linnets, redpolls, crossbills, and the canary, the bullfinches and hawfinches, and, more surprisingly, the Hawaiian honeycreepers, which evolved from a finch ancestor into forms ranging from seed-eaters to nectar and insect specialists. Many other small seed-eating birds are called finches informally but belong to other families.
Why were canaries used in coal mines?
Canaries and other small birds have a fast metabolism and breathe more air relative to their body size than a person, so they take in dangerous gases sooner and in higher effective doses. A caged canary carried into a mine would become distressed, stop singing, and fall from its perch when carbon monoxide, which is colourless and odourless, built up to levels still low enough for the miners to escape. Some mine canary cages were fitted with a small oxygen bottle and a door that could be sealed to revive the bird once it was carried back to fresh air. The practice continued in British mines until 1986, when electronic gas detectors replaced it.
What is the difference between a finch and a sparrow?
They are different families of small seed-eating songbird that overlap in appearance. True finches, Fringillidae, tend to have shorter, deeper, more sharply pointed conical bills, often brighter or bolder plumage with strong male and female differences, and a bounding flight, and they feed their young on regurgitated seed. Old World sparrows, Passeridae, are plainer and more uniformly streaky, with slightly less specialised bills, and their nearest relatives are the weavers. New World sparrows are yet another family. In North America, the naming is loose, with the house finch a true finch and several birds called sparrows or finches only distantly related, so the family is a better guide than the name.
Why do crossbills have crossed beaks?
The crossed bill tips are a tool for extracting seeds from tightly closed conifer cones. A crossbill slides its slightly open, crossed bill between two scales of a cone, then bites down, which forces the scales apart while the crossed tips act as a lever, and the bird's tongue, which has a hard scoop at the end, lifts the seed out. Chicks hatch with a straight bill that crosses as they grow, and the direction of the cross, upper bill to the left or right, is roughly fifty-fifty in a population and determines which way the bird holds a cone. This specialisation lets crossbills feed on a food source that is abundant but nearly inaccessible to other birds, at the cost of being tied to conifer forests.