Andaman Serpent-Eagle

Identificazione

The call of the Andaman serpent eagle consists of three to four short chip-sounding whistles. These birds are nearly entirely dark brown, except for their bright yellow faces and legs and they have spots on the tops of their wings and on their chests. They also have thick black bands on their tails and white and black bands on the underside of their wings. This species also has a hooked beak which is characteristic of a bird of prey and is used to tear apart food. Juvenile Andaman serpent eagles are known to have lighter colouring than adults and they also have a white head. Additionally, there is no sexual dimorphism between males and females, which means that it is impossible to differentiate the two sexes by physical characteristics alone.

Tassonomia

The genus Spilornis contains six species of serpent eagles, majority of which are island endemics. Serpent eagles are considered Old World birds because they are mostly found in Asia and Africa. In terms of taxonomy, the Andaman serpent eagle was originally thought to be a subspecies of Spilornis cheela before it was determined to be its own species. Since there is no complete taxonomic record for all of the species within Spilornis, it is difficult to determine exact relationships, although it is believed that the Andaman serpent eagle is an out group from the other Spilornis species. This means that the other Spilornis species are more closely related to each other than they are to the Andaman species. However, overall, even though they exhibit some variation, it has been determined that, because they are solely found in the Old World and mostly found on islands and in similar habitats, the species within Spilornis have very little genetic variation between them. This, along with the fact that they inhabit very similar territories, may explain why all of the species within the serpent eagle genus display very similar physical characteristics.

Nome scientifico

Spilornis elgini

Autorità

(Blyth, 1863)

Ordine

Accipitriformi

Famiglia

Accipitridae

Genere

Spilornis

Areale e habitat

The Andaman archipelago includes 204 islands, majority of which are forested, that all surround three main large islands. The Andaman serpent eagle has been found on all of the Andaman Islands, even on the islands with as little area as 0.8 km2 , although they prefer larger ones, and have even been known to occupy two different islands at the same time. They are usually found inland in closed canopy evergreen forests, on hillsides and in tropical lowland areas, however they can also be found closer to the coast and on agricultural land. Additionally, this species uses mangrove marshes and creeks as nesting sites. Thus, they have some very specific habitat requirements that need to be met in order to successfully reproduce and these areas are currently being disturbed, which is threatening the species.<p>In terms of population density, the Andaman serpent eagle is common within the archipelago it is endemic to, but its population size is actually quite small with fewer than 4000 individuals that are spread amongst various subpopulations. Individuals within this species tend to have a lifespan of 8 years.

Migrazione

Specie stanziale

Comportamento

Comportamento migratorio: Specie stanziale.

Conservazione

Tendenza della popolazione: in diminuzione.

Tendenza della popolazione

in diminuzione