The Juan Fernández archipelago comprises three principal islands of volcanic origin, located some 680-800 km west of continental Chile, to which it belongs politically. Isla Robinson Crusoe (or Más á Tierra, 93 km,²) and Isla Alejandro Selkirk (Más á Fuera, 85 km<+>) are the two islands with endemic birds (and therefore constitute this EBA), with none occurring on the third main island, Santa Clara. Land rises to 915 m at the dormant El Yunque on Robinson Crusoe and to 1,380 m at Los Inocentes on Alejandro Selkirk.

The climate is temperate and the islands were originally covered with forests of diverse origin. There are nearly 100 species of endemic flowering plant, including a monotypic family (the Lactoridaceae), several gigantic forms (e.g. the rhubarb Gunnera peltata), and numerous species of 'cabbage trees' of the endemic genus Dendroseris. Nineteen of the 54 ferns, including another monotypic family (Thrysopteridaceae), are endemic to the archipelago (Bourne et al. 1992). The native forest of Robinson Crusoe consists of evergreen trees dominated by Nothomyrica fernandeziana, Myrceugenia fernandeziana, Fagara mayu and Drimys confertifolia with a luxuriant understorey of ferns and epiphytes. The main native vegetation on Alejandro Selkirk is a tree-fern forest of Dicksonia externa on the wetter south-western part and Myrceugenia schulzei woodland on the higher land around Los Inocentes.

Sephanoides fernandensis is a bird of forest on both Robinson Crusoe (nominate race) and Alejandro Selkirk (race leyboldi), but is believed extinct on the latter island where it has not been recorded since 1908 (Brooke 1987, Meza 1989). Aphrastura masafuerae is confined to the Dicksonia externa fern-forests of Alejandro Selkirk (Brooke 1988, Hahn and Römer 1996), and Anairetes fernandezianus is found in all the scrub and remaining forested habitats of Robinson Crusoe.

Two species of seabird, Juan Fernández Petrel Pterodroma externa and Stejneger's Petrel P. longirostris, are endemic breeders to Isla Alejandro Selkirk.

The flora and fauna of the Juan Fernández Islands have declined drastically owing to the effects of two waves of introduced animals: goats, rats, cats and dogs introduced by the first colonists in the 1600s (though the dogs died out in the early 1800s), and then cattle, sheep, rabbits Oryctolagus cuniculus and coatis Nasua nasua introduced in the 1800s. The native flora has also been displaced by introduced plants, especially the shrub Aristotelia chilensis, bramble Rubus ulmifolius and the herb Acaena argentea (Bourne et al. 1992).

Much of the native forest has been cleared below an altitude of 500 m on both islands, and on Robinson Crusoe introduced species such as bramble provide the only vegetation cover. It is estimated that only 10% (5 km²) of the island is covered with natural vegetation and c.46% has suffered erosion (Hulm 1995).

Sephanoides fernandensis and Aphrastura masafuerae are both considered threatened. Summer numbers of S. fernandensis have been estimated at up to 800 birds, falling to 440 or so in winter, but there is also a long-term decline related to loss and degradation of natural vegetation, increased interspecific competition from Green-backed Firecrown S. sephanoides (as a result of that species' greater use of invasive exotic plants) and predation by introduced animals such as rats and coatis (Meza 1989, Collar 1992). The population of A. masafuerae was estimated at c. 500 birds in 1986 (Brooke 1988).

The islands are very important for seabirds (see 'Restricted-range species', above), with six species breeding, including the threatened Defilippe's Petrel Pterodroma defilippiana and Pink-footed Shearwater Puffinus creatopus (both classified as).

The entire archipelago, except San Juan Bautista village on Isla Robinson Crusoe, was designated a national park in 1935, and then a Biosphere Reserve in 1977. The Chilean government proposed a US$2.5 million restoration programme in 1995, and the islands have been nominated for World Heritage listing (Hulm 1995).

Recommended citation
BirdLife International (2024) Endemic Bird Area factsheet: Juan Fernández Islands. Downloaded from https://datazone.birdlife.org/eba/factsheet/61 on 22/11/2024.