The Galápagos Islands are widely known for their historical role in the development of the theory of natural selection and evolution. This volcanic archipelago, still one of the most active volcanic areas in the world, straddles the equator, some 960 km west of mainland Ecuador, to which it belongs politically. In all there are 13 islands of more than 10 km² (with Isabela the largest at 4,590 km²), and over 40 islets that have official names (with many small rocks and islets as yet unnamed). Most islands are below 900 m in elevation, although Isabela (1,710 m) and Fernandina (1,490 m) are considerably higher.

The vegetation of the islands has been divided into various zones: the littoral or coastal zone, which includes beaches, lagoons and mangroves; the arid zone, just inland from the coast, which is the most extensive habitat type on the islands with the greatest number of endemics, characterized by deciduous trees and shrubs; the transition zone, intermediate in character between the arid zone and the Scalesia zone, but dominated by different species, resulting in a diverse, mainly deciduous dense forest; the Scalesia zone, comprising lush evergreen cloud forest dominated by Scalesia pedunculata; and the open pampa zone consisting largely of ferns, grasses and sedges (Jackson 1985).

The archipelago's native biota demonstrates remarkable adaptive radiation. Both flora and fauna display a high degree of endemism, as would be expected in such an isolated tropical archipelago.

The restricted-range birds of the Galápagos are all endemic to the archipelago, and occupy most of the vegetation (and thus altitudinal) zones outlined above. Thirteen of the 22 endemics are known collectively as Darwin's finches (sometimes recognized as the separate subtribe Geospizini, with a fourteenth species on Cocos Island, EBA 022). The four Nesomimus mockingbirds constitute the next largest group of endemic species, and are indeed an endemic genus, all four species occurring in the littoral and arid zones. There are only four single-island endemics in Galápagos, these being Camarhynchus pauper and Nesomimus trifasciatus (on Floreana and satellites), N. melanotis (on San Cristóbal) and N. macdonaldi (on Hood), the remaining species generally being found on three or more islands (Harris 1982).

Six seabirds - Galápagos Penguin Spheniscus mendiculus, Waved Albatross Diomedea irrorata (also on Isla de la Plata), Galápagos Petrel Pterodroma phaeopygia, Galápagos Cormorant Phalacrocorax harrisi, Lava Gull Larus fuliginosus and Swallow-tailed Gull Creagrus furcatus - are endemic breeders to the islands, but are not included in the EBA analysis. White-vented Storm-petrel Oceanites gracilis is known to breed only in this EBA and on Isla Chungungo off Chile.

The islands' wildlife is threatened as a result of various human activities: overgrazing by domestic and feral livestock, predation by exotic species, fires started by man, and poaching (Dinerstein et al. 1995).

Three of the endemic landbirds are presently considered threatened, all for slightly different reasons. Buteo galapagoensis occupies c.130 breeding territories (but exhibits cooperative polyandry), and has declined due to human persecution, and partly from a reduction in prey items (caused by introduced predators). Nesomimus trifasciatus now occurs only on Floreana’s two satellite islands, where the population stands at c.300 birds and thus requires constant management. Camarhynchus heliobates is very poorly known, occurring on Fernandina and Isabela in an area of mangrove totalling some 5 km² (Collar et al. 1992).

Additionally, four of the endemic seabirds are considered to be threatened: Spheniscus mendiculus (classified as Vulnerable),Pterodroma phaeopygia (Critical), Phalocrocorax harrisi (Vulnerable) and Larus fuliginosus (Vulnerable); Oceanites gracilis is classified as Data Deficient (Collar et al. 1994). Diomedea irrorata should also be considered threatened and is treated as such in Croxall and Gales (in press).

The entire Galápagos archipelago is formally protected as a national park and Biosphere Reserve (IUCN 1992a), and as a World Heritage Site. However, with so many island-adapted endemics, constant vigilance needs to be exercised by the large number of tourists and resident scientists to prevent the accidental introduction of further alien species (especially predators) to islands where the native flora and fauna would probably be unable to compete. Efforts to eradicate existing alien species could only benefit the vulnerable native flora and fauna.

Recommended citation
BirdLife International (2024) Endemic Bird Area factsheet: Galápagos Islands. Downloaded from https://datazone.birdlife.org/eba/factsheet/43 on 22/11/2024.