Crested Serpent Eagle

The crested serpent eagle, Spilornis cheela, is a medium-sized raptor with a robust build, characterized by its dark brown plumage, rounded wings, and short tail. Its most distinctive feature is the short black and white fan-shaped nuchal crest, which imparts a thick-necked appearance. The face is bare, with striking yellow skin that extends to the ceres, and the powerful feet are unfeathered, displaying heavy scaling. The underside is adorned with white and yellowish-brown spots, and when perched, the wingtips fall short of the tail tip. In flight, the broad wings form a shallow 'V', and the tail and underside of the flight feathers exhibit bold black and white bars.

Size

The crested serpent eagle exhibits remarkable size variation among its subspecies, with total lengths ranging from 41 to 75 cm (16 to 30 in) and wingspans from 89 to 169 cm (2 ft 11 in to 5 ft 7 in). The largest race is the nominate S. c. cheela, while the smallest is likely S. c. minimus, exhibiting a form of insular dwarfism. Weights vary widely, with some subspecies weighing as little as 420 g (15 oz) and others potentially reaching up to 2,300 g (81 oz).

Taxonomy

This species is part of the subfamily Circaetinae, which includes snake eagles. There are 21 proposed subspecies, with considerable variation in size and coloration. Some island-dwelling taxa are smaller due to insular dwarfism. The taxonomy is complex, with some authorities suggesting that certain subspecies should be treated as separate species.

Behaviour and Ecology

The crested serpent eagle is a reptile specialist, hunting snakes and lizards over forested habitats and wet grasslands. It also preys on various other animals, including birds and mammals. This species is mostly sedentary, with some populations being migratory. They spend much of their time perched, calling frequently with a loud, piercing three or two-note call. Males in Taiwan have been observed to have larger home ranges than females. The species uses a sit-and-wait hunting strategy and is known to roost in densely foliaged trees.

Song & Calls

The call of the crested serpent eagle is a distinctive and rising "Kluee-wip-wip," often heard in the late mornings.

Breeding

The breeding season starts in late winter, with eggs laid in early summer. Nests are large platforms built high in trees, often refurbished and reused. The female incubates the eggs, while the male guards. Chicks fledge after about two months, and if eggs are lost, a replacement clutch may be laid.

Similar Species

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Diet and Feeding

The crested serpent eagle's diet consists primarily of reptiles, particularly snakes, but also includes birds, amphibians, mammals, fish, termites, and large earthworms. They have been observed following snakes on the ground and employ a sit-and-wait foraging strategy.

Conservation Status

The crested serpent eagle is listed as Least Concern by the IUCN. However, some subspecies, particularly those on small islands, have small populations and may be at risk. The Bawean serpent eagle, for example, is critically endangered with a declining population.