Nests are double-layered with an outer layer of twigs and an inner one of grass, rootlets and moss. The clutch size is unknown. Young birds fledge from mid-July, with the adults moulting from September onwards. Feeding The Azores bullfinch's diet is mainly herbivorous, with the birds consuming a range of seeds, fruits, flower buds, fern sporangia and fronds (unusual in birds), and moss tips, as well as some invertebrates such as hemiptera. Native vegetation is preferred although, when the range was more extensive in the 19th century, the species was considered to be a pest in orange orchards around Furnas. The bullfinches move up and downslope through their range according to food availability during the year. The lily of the valley tree (Clethra arborea) contributes greatly to the Azores bullfinch's diet. This evergreen shrub or small tree, once believed to be endemic to Madeira, but now known to have existed in the past on the Canary Islands (where it is considered extinct), raises questions about how it should be treated in the Azores. While it is considered exotic, it is possible that it was native to the Azores, disappeared from there before any botanist had the chance to record it, and was then reintroduced more recently. Despite being an "alien" species, it is a notable element of the bird's diet and therefore plays some role in its survival. Status and conservation The population of the Azores bullfinch is small; it was estimated to comprise 30–40 pairs in the late 1970s, 100 pairs in 1989, and between 60 and 200 pairs in the early 1990s, though in 2008 it was estimated at 775 individuals. It is the most threatened passerine bird and the second rarest bird behind the northern bald ibis (Geronticus eremita) in Europe. The population was once larger and spread over a wider range, but both numbers and range have declined since the 1920s following the destruction of areas of its forest habitat for grazing and agriculture, as well as afforestation and invasion by introduced plants, especially the Japanese cedar (Cryptomeria japonica). The entire range of the species is protected as a Special Protection Area, the Pico da Vara / Ribeira do Guilherme SPA (a Natura 2000 site), under European Union legislation. The main approach to conserving the species is the protection and restoration of threatened native laurel forest vegetation. References Notes Works cited Bibby, Colin J.; Charlton, Trevor