| Long-tailed Ground Roller | |
|---|---|
| Adult Long-tailed Ground Roller in Mangily, Madagascar | |
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Coraciiformes |
| Family: | Brachypteraciidae |
| Genus: | Uratelornis Rothschild, 1895 |
| Species: | U. chimaera |
| Binomial name | |
| Uratelornis chimaera Rothschild, 1895 |
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The Long-tailed Ground Roller (Uratelornis chimaera) is a species of bird in the family Brachypteraciidae, and is placed in the monotypic genus Uratelornis. This bird is endemic to arid spiny forests near the coast in southwestern Madagascar. It occurs in extremely low population densities throughout its habitat. It requires shade and a deep layer of leaves in its habitat, and it is absent from parts of the spiny forest lacking these traits. It has no recognized subspecies, and its closest relative is believed to be the Scaly Ground Roller. The Long-tailed Ground Roller is the only ground roller to definitively display sexual dimorphism, or differences in plumage or size between sexes. It is a medium-sized bird with a plump silhouette and a long tail. The upperparts are dark brown with black streaks while the underparts are light gray. The white throat is framed by black malar stripes and a black breastband, while a white stripe is present at the base of the bill. Sky blue feathers are visible at the edge of the wings and the tail. Calls are rarely made outside of the breeding season, though multiple territorial calls are made.
These ground rollers feed primarily on invertebrates, ranging from worms to butterflies. The bird searches through deep leaf litter for its prey or waits attentively for an opportunity. Its wings are relatively weak, so the ground roller primarily uses its strong legs to run through its habitat. The Long-tailed Ground Roller is a monogamous species, and defends a territory during the breeding season of October to February. The species digs a tunnel in the sand, at the end of which is a wider chamber where it makes its nest out of leaves and earthy pellets. Two to four eggs are laid. After the chicks fledge, the birds continue living in family groups for an unknown period of time after the breeding season before dispersing across the habitat.
This species is classified as Vulnerable, and is threatened by habitat destruction.[1] The arid spiny forests in which it lives are unprotected by the Madagascan government, and as such the species is losing habitat to slash-and-burn agriculture, charcoal collection, and logging. The species is also hunted by the native peoples of Madagascar.
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The Long-tailed Ground Roller was described by British banker and naturalist Walter Rothschild in 1895. Rothschild described the species as Uratelornis chimaera, and published his description in the periodical of his private museum, Novitates Zoologicae. The Long-tailed Ground Roller is currently placed in the ground roller family.[2] However, until recently the ground rollers, Cuckoo Roller, and rollers were all placed in a single family in which each of the three groups formed a subfamily.[2] In 1971 Joel Cracraft proposed erecting a separate family for the ground rollers based on dramatic differences in behavior, plumage, and post-cranial anatomy between the groups.[3] This position is supported by DNA evidence, which also removed the Cuckoo Roller from the group.[4] It has been suggested but not widely accepted that the ground rollers are closely related to the puffbirds and jacamars.[2] It is believed that the ancestor of the Long-tailed Ground Roller was an arboreal roller that invaded Madagascar from Africa and developed a terrestrial lifestyle before moving from the rainforests into the Long-tailed Ground Roller's arid scrubland.[2] The adaptations required for the ancestral Long-tailed Ground Roller to inhabit scrubland led Rothschild to create the monotypic genus Uratelornis for the species in his description.[2] No fossils have been found for this genus.[4] Recent genetic analysis suggests that this species' closest relative is the Scaly Ground Roller.[4] This species has no subspecies.[5]
The Long-tailed Ground Roller is the only ground roller to definitively display sexual dimorphism.[2] It is highly distinctive from a distance due to its long tail and plump silhouette.[6] The bird is 34 to 47 centimetres (13 to 19 in) long, although its tail can contribute up to 30 centimetres (12 in) of the length.[5] This tail is the longest of the ground rollers.[6] This ground roller has short wings and long, pinkish-brown legs.[7] The male has a sandy buff crown and dark brown upperparts with black streaks.[5] Its supercilium is a pale buff color, while the ear-coverts are brown.[5] The eyes are brown and the short and stout beak is black.[1][5] Its tongue is long with a brush-like tip to help it collect insects.[2] A white stripe is present from the base of the bill and is surrounded by brown and black malar stripes. These malar stripes and the black breastband frame a white throat.[5] The tail has 15 to 20 dark brown bars marking it, while the outer retrices are sky blue. This sky blue is also present on the wing-coverts.[5] In flight, its two black and white bands on the primaries and secondaries are conspicuous.[5] The underparts are a light gray, and the breast white.[5] The toes are zygodactylous, with the first and fourth toes turned outwards and the middle two toes turned inward.[7] The female resembles the male but is smaller and has a narrower chestband and a shorter tail.[5][8] Additionally, the female Long-tailed Ground Roller loses its tail while nesting.[7] Juveniles of both sexes are duller in plumage than the adult female, particularly in the black bands on the chest, neck, and eye.[6]
This ground roller is largely a silent species except during the breeding season.[6][9] Its vocalizations include a "hooting" sound, a "popping" tu-tuc, and a soft boo sound.[8] The low-pitched "hooting" is given from a perch 2 to 6 metres (6.6 to 20 ft) above the ground at dusk or at night. The sound carries for a distance of at least 200 metres (660 ft) and it has been suggested that this song attracts a mate or is used to defend a territory. The bird pumps its tail while giving this call.[8] The territorial call is a series of soft "boo" notes, typically coming in sets of six to ten and descending near the end.[5] Another territorial call has been described as a series of chuckling tu-tuc sounds lasting between 10 and 40 seconds that occasionally ends in a loud snapping sound produced by the wings.[5][8] This call is given when birds are close to each other and on the ground or low perches and does not carry over long distances. The use of wing-snapping to produce a sound is a rare phenomenon in birds, and only one other family in the order Coraciiformes, the todies, is known to do it.[8] Low "gu" notes are given by mates as they come in contact with each other.[5]
The Long-tailed Ground Roller is endemic to the island nation of Madagascar. It inhabits a narrow strip of suitable habitat by the coast in the southwestern part of the island.[10] This strip is bordered by the Mangoky River in the north, the Fiherenana River in the south, and lowland hills in the east.[5] It totals about 10,500 square kilometres (4,100 sq mi) in area; however, the species is extremely uncommon within its range and occurs at densities of about 0.008 to 0.1 per 10,000 square metres (110,000 sq ft).[1] This area ranges in elevation from sea level to 100 metres (330 ft).[5] It does not migrate, though it is believed to disperse across a broader stretch of habitat outside of the breeding season.[9]
This species' prime habitat is a mix of sub-arid thorn-scrub and deciduous woodland. This area only averages 500 millimetres (20 in) of water a year and is covered in sandy soil.[10] The dominant plants in this spiny forest belong to the cactus-like Didiereaceae family (especially Didierea madagascariensis) and more tree-like Euphorbiaceae family (especially Euphorbia stenoclada).[11] Baobab trees are also prevalent.[5] It formerly was believed that the Long-tailed Ground Roller preferred undisturbed forest habitat, despite tolerating small amounts of disturbance.[10] However, recent studies have concluded that it actually prefers degraded habitat.[1] However, shade is necessary and the species is not found in deforested habitat or on the shadeless dunes prevalent in its range.[1][5]
The Long-tailed Ground Roller is a shy and elusive bird.[10] If seen, it either freezes or runs away. Due to its short wings, the species rarely flies, but it is a powerful runner.[11] While largely terrestrial, it roosts in low trees and bushes and sings from low perches.[1] The Long-tailed Ground Roller is a solitary species outside of the breeding season. It is diurnal, though, unusually for a ground roller, it occasionally forages at night.[10] When calling, this species bobs its head and raises its tail.[12] The Long-tailed Ground Roller also raises its tail when it is excited.[12]
This species forages almost exclusively from the ground.[12] It alternates between attentively waiting for prey and actively searching for it by rummaging through deep leaf litter.[10] It eats invertebrates and occasionally small vertebrates.[12] This ground roller eats a wide range of invertebrates, including ants, beetles, butterflies, caterpillars, cockroaches, grasshoppers, woodlice, and worms. Despite the Long-tailed Ground Roller's poor flying abilities, it has been seen catching butterflies in midair.[5]
The breeding season coincides with the rainy season, lasting from October to January.[5] During the breeding season this species abandons its solitary habits to pair with another Long-tailed Ground Roller, to which it remains monogamous. Males also form territories during the breeding season, defending their area with territorial calls.[13] These calls are given from a perch up to 6 metres (20 ft) off of the ground for an hour after sunrise and occasionally throughout the day and night.[5] Males have been observed feeding the female during courtship.[13]
Long-tailed Ground Rollers use both their bill and feet to excavate a burrow in consolidated sand and construct their nest at the end of it.[14] The burrow, always constructed away from grassy vegetation, is downward-sloping. The burrow is between 0.8 and 1.2 metres (2.6 and 3.9 ft) long and has a diameter of 8 centimetres (3.1 in). The end of the burrow widens into a 20 centimetres (7.9 in) wide chamber with a shallow floor covered in dry leaves and earthy pellets.[13] When digging its nest, the Long-tailed Ground Roller occasionally walks underneath a low branch, tilts its head upwards, and, while remaining motionless, releases a rising crescendo of its "tu-tuc" calls. At the height of the crescendo the bird breaks off its call and flies upwards onto the branch while producing a "ripping and crackling sound" with its wingbeats.[8] From the perch the bird releases a stream of "boo" notes. It is believed that this display is part of a courtship ritual.[8]
Between October and January, peaking in November, the species lays two to four eggs, normally two.[1][13] The eggs are smooth and white.[13] After the young fledge, they still live in a family group of four to five birds for an unknown period of time before the family disperses.[10]
The Long-tailed Ground Roller has been classified as Vulnerable by the IUCN due to ongoing habitat destruction and a decline in the quality of remaining habitat.[1] It is believed to be the most threatened species of ground roller.[5] Thirty percent of its already small habitat area was degraded between the mid-1970s and 2000. Slash-and-burn agriculture, charcoal production, logging, and cattle grazing contributed to the loss of habitat.[15] As of 2011, no reserves protect any portion of its habitat, and as a result its habitat has been described as the area of Madagascar most in need of conservation efforts.[1][16] It is also threatened by both hunting and egg-collecting. In addition to humans, dogs hunt this species and the introduced black rat is believed to be a nest predator.[15] This species is capable of tolerating some habitat disturbance, but requires a suitable amount of shade and leaf litter to continue living in the area.[10] The estimated population of the Long-tailed Ground Roller is between 9,500 and 32,700 birds and declining.[1]
The local inhabitants of Madagascar believed, as this bird is remarkably silent and difficult to see during the non-breeding season, that the Long-tailed Ground Roller hibernated in its burrows, although no evidence supports this. While not particularly tasty, this species is hunted for food due to its large size and the relative ease of capture compared with arboreal birds.[9] This bird has been featured on several of Madagascar's stamps.[17] Only one zoo, Germany's Weltvogelpark Walsrode, is known to keep this species.[18] It is considered by birdwatchers to be one of the world's most elusive birds.[19]