Short answers, pulled from the story.
The canary served as an early warning system for carbon monoxide in coal mines from the eighteenth century until the practice ceased in the UK in 1986. Miners relied on the bird to detect the invisible, odorless gas that killed workers because its delicate physiology reacted to the gas far more quickly than any human could. When the air became toxic, the bird would stop singing and collapse, giving the miners time to escape.
The English zoologist William Elford Leach introduced the name Fringillidae in a guide to the British Museum in 1819. The relationships between the species remained murky until the 1990s when a series of phylogenetic studies based on mitochondrial and nuclear DNA sequences began to untangle the web. These genetic analyses revealed that the Neotropical Euphonia and Chlorophonia were actually more closely related to the finches.
The family Fringillidae contains more than two hundred species divided into fifty genera. The largest groups are the Carduelinae, which includes 183 species divided into 49 genera, and the Euphoniinae, which contains the Euphonia and Chlorophonia. The smallest classical true finches are the Andean siskin, measuring as little as 9.5 centimeters, while the largest is the collared grosbeak, reaching up to 23 centimeters in length.
True finches are conspicuously absent from Australia, Antarctica, the Southern Pacific, and the islands of the Indian Ocean. They occupy a near-global distribution found across the Americas, Eurasia, and Africa. This global diversity is further complicated by the fact that many birds in other families are also commonly called finches, such as the estrildid finches of the Old World tropics.
The primary diet of true finches consists of seeds, though some species like the euphoniines include considerable amounts of arthropods and berries. The Hawaiian honeycreepers have evolved to utilize a wide range of food sources, including nectar, while the diet of Fringillidae nestlings includes a varying amount of small arthropods. This ability to adapt their diet has allowed finches to become one of the most successful and widespread groups of birds on the planet.