Finch

• 1. Introduction

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  From the eighteenth century to the twentieth, miners in the UK, the US, and Canada carried finches and canaries underground. The birds were not pets. They were instruments. A finch falling silent or collapsing warned of carbon monoxide before any human nose could detect it. In the UK, this practice did not end until 1986. That small, conical-billed bird trusted with a miner's life belongs to a family far stranger and larger than most listeners imagine. The true finches make up the family Fringillidae, more than two hundred species spread across fifty genera, with a worldwide native range broken only by Australia and the polar regions. Yet much of what people casually call a finch is not a true finch at all. So what makes a finch a finch, why has its family tree been rebuilt by DNA, and how did one branch wander into Hawaii and erupt into a riot of forms?

• 2. What Counts As A Finch

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  Stout conical bills, adapted for cracking seeds and nuts, define the true finches more than any other single trait. Many wear colourful plumage, and unlike so many small birds they are usually resident, staying put rather than migrating across seasons. The family includes the canaries, siskins, redpolls, serins, grosbeaks, and euphonias, plus the morphologically divergent Hawaiian honeycreepers. The word finch, though, has been borrowed loosely. The estrildid finches of the Old World tropics and Australia belong to their own family, Estrildidae, with no true-finch membership. Some birds called finches sit instead in the Old World bunting family Emberizidae or the New World sparrow family Passerellidae. Even the celebrated Darwin's finches of the Galapagos islands are now counted among the tanagers, in the family Thraupidae. The name itself was a deliberate act. In 1819, the English zoologist William Elford Leach introduced Fringillidae in a guide to the contents of the British Museum, fixing the label that scientists still argue over today.

• 3. Rewriting The Family Tree

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  In 1968, the American ornithologist Raymond Andrew Paynter, Jr. confessed the depth of the problem. He wrote that the limits of the genera and relationships among the species were less understood, and subject to more controversy, in the carduelines than in any other passerines, with the possible exception of the estrildines, the waxbills. The trouble came from convergence: unrelated birds settling into similar niches and evolving similar shapes, fooling anyone who classified by appearance. Beginning around 1990, studies of mitochondrial and nuclear DNA sequences forced a sweeping rewrite. The Neotropical Euphonia and the Chlorophonia, once filed with the tanagers because they looked the part, turned out to be closer kin to the finches and now form their own subfamily, Euphoniinae. The three largest genera collapsed under scrutiny, each found to be polyphyletic and each split apart. The American rosefinches were moved from Carpodacus to Haemorhous. Carduelis lost its greenfinches to Chloris and a large clade to Spinus, keeping only three species. Thirty-seven species departed Serinus for Crithagra, leaving eight behind. Today Fringillidae sorts into three subfamilies: the Fringillinae with its single genus of chaffinches, the Carduelinae with 183 species across 49 genera, and the Euphoniinae. One bird refused to fit anywhere. Przewalski's rosefinch, Urocynchramus pylzowi, carries ten primary flight feathers rather than the nine all other finches share, and now stands alone in its own family, Urocynchramidae, with no close relatives among the Passeroidea.

• 4. The Honeycreeper Explosion

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  Hawaiian honeycreepers were once granted a family entirely their own, Drepanididae, before DNA placed them inside the finches, beside the Carpodacus rosefinches, within the Carduelinae. What sets them apart is the bill. While most true finches carry strong, stubby beaks, the honeycreepers became famous for a wide range of bill shapes and sizes produced by adaptive radiation, a single ancestral stock fanning out to exploit different foods. Their diets broke the granivorous mold of the family, reaching even into nectar. The cost of that experiment is written in extinction. The Carduelinae now counts 18 extinct Hawaiian honeycreepers, alongside the extinct Bonin grosbeak. The genus Melamprosops holds a single extinct species, the po'ouli. Drepanis contains two extinct species, the Hawaii mamo and the black mamo, with only the iiwi still living. Hemignathus has four species, of which just one survives. The roll of lost birds keeps lengthening, from the Kona grosbeak in Chloridops to the Lanai hookbill in Dysmorodrepanis.

• 5. Built To Crack Seeds

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  The Andean siskin, Spinus spinescens, can measure as little as 9.5 centimetres, while the lesser goldfinch, Spinus psaltria, weighs as little as 8 grams, marking the small end of the classical true finches. At the other extreme stands the collared grosbeak, Mycerobas affinis, reaching up to 24 centimetres and 83 grams. Even greater figures have been logged in species slightly smaller on average: lengths to 25.5 centimetres in the pine grosbeak, Pinicola enucleator, and weights to 86.1 grams in the evening grosbeak, Hesperiphona vespertina. Beneath the variation lies a shared body plan. Every true finch carries 9 primary remiges and 12 rectrices, the flight and tail feathers counted by the bird in the hand. Their colour leans brownish, sometimes greenish, often with considerable black, while white shows up mainly as wing-bars or signalling marks. Bright yellow and red carotenoid pigments run through the family, which is why blue structural colours are rare; the yellow pigment turns blue into green. In many species the sexes differ sharply, with females lacking the bright carotenoid markings of the males.

• 6. Where Finches Live

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  The Americas, Eurasia, and Africa all hold native finches, joined by island groups such as the Hawaiian islands, giving the family a near-global reach. The map has hard edges. Finches are absent from Australasia, Antarctica, the Southern Pacific, and the islands of the Indian Ocean. Human hands have blurred even that boundary, carrying some European species into Australia and New Zealand, where they were widely introduced. Well-wooded areas are their usual home, yet the family is not bound to forest, with some species turning up on mountains or even in deserts. Their movement through the air follows the small-passerine pattern, a bouncing flight that alternates bouts of flapping with gliding on closed wings. The fossil record offers only thin testimony. True-finch fossils are rare, and most that exist can at least be matched to living genera. The family appears to trace back to roughly Middle Miocene origin, around 20 to 10 million years ago, and an unidentifiable finch fossil from the Messinian age, around 12 to 7.3 million years ago, has been recovered at Polgardi in Hungary.

• 7. Singers And Survivors

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  Most finches sing well, and several are kept as cagebirds, foremost among them the domesticated canary, Serinus canaria domestica. Their nests are basket-shaped, usually set in trees, more rarely tucked into bushes, between rocks, or on similar substrate. The family eats mainly seeds, but the diet is not uniform. The euphoniines take considerable amounts of arthropods and berries, and the Hawaiian honeycreepers stretched the menu furthest, evolving to use food sources as varied as nectar. Even seed-eaters feed their young differently; the nestlings of Fringillidae take in a varying amount of small arthropods. By the final tally the family Fringillidae holds 235 species across 50 genera and three subfamilies. Within that count sit some of the smallest stories of loss in the bird world, like the genus Ciridops, which keeps a single recently extinct species, the Ula-ai-hawane, alongside three prehistoric ones, a reminder that the family's ledger records the vanished as carefully as the living.