They’re the natural symbol of Tenerife and endemisms of the Canary Islands. They’re restricted to the pine tree forests of Tenerife and Gran Canaria between 800 and 2000 meters above sea level, feeding on pine nuts with their robust bills. They prefer pine tree forests with an undergrowth of Chamaecytisus proliferus or Adenocarpus foliolosus, the seeds of which are also part of its diet. There areas where the pine tree forests possess elements of monteverde forest, they share the habitat with the endemic subspecies of the common chaffinch (Fringilla coelebs canariensis) that, similarly, has evolved to have blue dorsal feathers. During the spring, they are attracted by the fruit-bearing high mountain shrubs from Cañadas del Teide. They’re solitary birds but often like to move in small groups. F. teydea from Tenerife is locally common, with over 1000 couples, but F. polatzeki from Gran Canaria is endangered at an estimated 250 couples and restricted to 2 different populations: the forest of Tamadaba in the north, and the forests of Ojeda, Pajonales and Inagua in the south. Inagua has unfortunately suffered a wildfire in 2007 that destroyed 18 775 ha of forest, being the core of its distribution, this nearly extinguished the species.
It’s an elegant bird of a singular beauty; blue is an extremely rare color in nature and only a handful of animals sport blue in their coloration. But those that do, don't do halfway with blue. Some plants can produce blue pigments thanks to anthocyanins, but blue is incredibly rare in the animal kingdom, and most animals are unable to make true blue pigments. The only animal in the world known to be able to create a blue pigment is an uncommon butterfly: the Obrina olivewing (Nessaea obrinus). All the other blue colors in the animal kingdom are achieved through microscopic structures that cancel out light of most wavelengths by phasing out part of that light in a way that it is neutralized, only blue has the right wavelength for all of the reflected light to be in sync, resulting in a blue color. This is how blue chaffinches get their well-known coloration that has given them their name.
The male of the species from Tenerife is strikingly colored, with a slate-blue bill and plumage, save for the vent and underwing coverts which are white, and the caudal, primary and secondary remiges which are black. The male of the species from Gran Canaria has more of a cinereous-blue coloration and with two characteristic white bands on its wing. The female of both subspecies is olive-green and therefore similar to the female of the common chaffinch, although lacking the white scapular feathers. This resemblance is due to the fact that they're very closely related to the common chaffinch, but they differ not only in coloration but also in their greater size. It is believed the ancestors of these two species arrived from North Africa in a wave prior to that of the common chaffinch. The song can be rather melodious, but it is usually a “chooey chooey” for F. teydea, and “ventooey” for F. polatzeki.