Grey-necked wood rail
|Grey-necked wood rail|
|Grey-necked wood rail|
The grey-necked wood rail or grey-cowled wood rail (Aramides cajaneus) is a species of bird in the family Rallidae, the rails. It lives primarily in forests and mangroves of Central and South America. It also lives in swamps. It is usually not found at elevations above 2,000 metres (6,600 ft), although some have been recorded at 2,300 metres (7,500 ft) above sea level. This bird's large extent of occurrence, along with other factors, is why it is considered to be least-concern by the International Union for Conservation of Nature (IUCN). In some places, it is occasionally hunted and kept for food.
This bird, large for a wood rail, has both a grey head and, as the name implies, neck. In the nominate, the back of the head has a brown patch. The upperparts are olive-green to dark brown. The chest and flanks are a rufous colour, with the belly, rump, and tail being black. The legs are coral-red, the bill is a bright greenish-yellow, and the eyes are red. The sexes are similar. The juveniles can be differentiated by their duller look, and the precocial chicks can be identified through their black, downy appearance, brown head, and black beak. The subspecies avicenniae can be differentiated by its smaller size, lack of a brown patch at the back of the neck, and its lower back being toned slightly olive. The underparts are also pale.
This bird is monogamous, and partners can be found together throughout the year. During the breeding season that usually lasts from March to August, the grey-necked wood rail builds nests that can be found on flat branches and in thickets, usually at heights between 1 and 3 metres (3.3 and 9.8 ft). In these nests, there is a clutch consisting of three to seven eggs, incubated by both sexes. The chicks that hatch are precocial. This bird feeds on a wide range of foods, from molluscs to seeds. It is additionally known to feed on the feces of giant otters.
Taxonomy and etymology
Placed in the family Rallidae—the rails—this species was originally described as Fulica Cajanea by Philipp Ludwig Statius Müller, in his 1776 Vollständiges Natursystem. It was eventually moved to the genus Aramides, in addition to the specific epithet being changed to cajaneus.
The grey-necked wood rail is regarded as being sister species with the rufous-naped wood rail. The number of subspecies is contentious, some recognize up to nine, while others recognize only two. It is even suggested that the subspecies avicenniae be split into its own species, based on differences in morphology and calls, speculated to have arisen because the slaty-breasted wood rail acted as an ecological barrier between the two subspecies. The subspecies, according to the International Ornithologists' Union, are:
- Aramides cajaneus cajaneus — (Müller, 1776) — from Costa Rica to Colombia, east through Venezuela and Trinidad to Brazil, and south to Northern Argentina and Uruguay
- A. c. avicenniae Stotz, 1992 — coastal southeastern Brazil
Other subspecies tentatively recognized include A. c. albiventris, plumbeicollis, mexicanus, pacificus, vanrossemi, morrisoni, and latens. Of these, one has become a full species, albiventris, the rufous-naped wood rail, while the others have become subspecies of it.
The genus name of the grey-necked wood rail—Aramides—is derived from the combination of the genus Aramus and of the Greek oidēs, "resembling". This refers to the similarity between birds of the genus Aramides and those of the genus Aramus. The specific epithet, cajaneus, is in reference to the capital city of French Guiana, Cayenne. The subspecies epithet avicenniae honors the Persian philosopher Avicenna.
The grey-necked wood rail usually measures 33–40 centimetres (13–16 in) long and weighs 320–465 grams (11.3–16.4 oz), particularly large for a wood rail. The upperparts are olive-green to dark brown. The head and neck are medium-grey, blending into a brown patch at the back of the head. The eyes are red. The chest and flanks are rufous. The belly, rump, and tail are black. The legs are coral-red, while the bill is a bright greenish-yellow. The males and females are similar.
Juvenile birds are similar to the adult but are duller in colour, with their belly sooty-black and flecked with buff. The juveniles also differ in the fact that their bill and legs are dusky, and have brownish eyes. The chicks are black and downy, with a brownish head. Their dark eyes are lined with dull, reddish bare skin. The black bill has a flesh-coloured base, and a small, white egg tooth behind the tip of the upper mandible, in addition to a very small one at the tip of the lower mandible.
The subspecies avicenniae differs from the nominate by its smaller size. It also varies as its nape to back is a dull grey colour. The brown spot present at the back of the head of the nominate is also reduced or gone. The lower back is toned a slight olive, and the underparts are also slightly paler than the nominate, but without white feathers. Additionally, avicenniae's upper wing-coverts are more greenish-grey.
The grey-necked wood rail has a loud, repetitive cackling call mainly heard at dawn and dusk: pop-tiyi pop-tiyi co-co-co-co-co or chitico chitico cao-cao-cao. These songs are often sung in a chorus or duet. The alarm call is a harsh, loud cackle or clucking shriek.
Distribution and habitat
It is found in Argentina, Bolivia, Brazil, Colombia, Costa Rica, Ecuador, French Guiana, Guyana, Panama, Paraguay, Peru, Suriname, Trinidad and Tobago, Uruguay, and Venezuela. The nominate subspecies is found in all of the aforementioned countries except Suriname and Trinidad and Tobago. It is, although, cut off by the Andes Mountains and lies east of them in Ecuador, Peru, and Bolivia. Additionally, it is not found in the southeastern interior of Brazil. The subspecies avicenniae is found in Coastal Brazil, São Paulo, south to Panama.
The grey-necked wood rail's natural habitats are subtropical or tropical moist lowland forests, subtropical or tropical mangrove forests, and subtropical or tropical swamps. The subspecies avicenniae, however, is almost completely restricted to mangrove forests. The grey-necked wood rail is not usually found above elevations of around 2,000 metres (6,600 ft), although some wanderers have been recorded at elevations up to 2,300 metres (7,500 ft) in Colombia.
Behaviour and ecology
The grey-necked wood rail's nests are usually 1 to 3 metres (3.3 to 9.8 ft) off the ground, built on flat branches or in thickets. The nests are lined with twigs and leaves. They generally have a diameter between 30 and 40 centimetres (12 and 16 in) on the outside, with an internal diameter of around 15 centimetres (5.9 in). The depth is usually between under 4 and 9 centimetres (1.6 and 3.5 in). The overall height of the nest is around 16 centimetres (6.3 in).
This bird is monogamous, forming long lasting pair bonds, with pairs of gray-necked wood rails staying together throughout the year. The breeding season of this bird usually occurs between March and August, although this varies depending on geography. In Costa Rica, the breeding season extends until September. In Mexico, on the other hand, the breeding season is known to start as early as January.
The clutch this bird lays usually consists of three to seven brown-blotched, slightly glossly, whitish eggs, although clutches consisting of five eggs are most typical. These eggs usually measure around 52 by 36 millimetres (2.0 by 1.4 in) and weigh between 25.1 and 27.1 grams (0.89 and 0.96 oz). They are incubated by both sexes, each taking six to eight hour shifts, for around 20 days. In captivity, the male incubates during the day, and the female during the night. The chicks hatch precocial and are cared for by the parents for one or two days before leaving the nest, although chicks sometimes use the brood nest until they are 40 days old.
This bird feeds at night, eating various invertebrates and small vertebrates. While in mangroves, it commonly feeds on crabs. Otherwise, it will generally feed on molluscs, arthropods, frogs, seeds, berries, palm fruits, and the occasional water snake. Maize, rice, and bananas are also viable food items for the grey-necked wood rail. It is also known to feed on the feces of giant otters at latrines.
When eating snails, this bird will hammer at the shells to extract them. For berries, this bird will jump high to break off clusters of this fruit. After doing this, it will pick off the berries one by one and eat them. It uses its partially open bill to probe and move aside debris like leaf litter. It is generally wary and secretive, in addition to being selfish when mated. This manifests in warning its partner with threat displays to keep it at a distance. Even so, it has occasionally been seen to openly forage in short grass near thickets and in streams or muddy tracks.
The grey-necked wood rail is the type host of Plasmodium bertii, an apicomplexan parasite, meaning that P. bertii was originally discovered on this organism. P. lutzi is also found on this bird.
This rail is considered to be a least-concern species, according to the IUCN. The justification is this bird's stable and large population, believed to be somewhere between five million and 50 million individuals. The grey-necked wood rail also has a large extent of occurrence, estimated to cover 21.4 million square kilometres (8.3 million sq mi). It is common throughout its range, although it is adversely affected by destruction of its habitat.
This bird is occasionally hunted for food in northeast Brazil. They are usually hunted with baited fish hooks that are laid near the bodies of water where these birds forage. In the Las Minas District, in Panama, this bird is also kept for food.
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