Ocellated Crake
Rufirallus schomburgkii
A tiny rail found in dense grasslands, often far from water. Extremely difficult to see, but striking plumage renders this species unmistakable: look for warm orange crown and breast, bold white spotting on upperparts, and pink legs. Far more often heard than seen. Listen for a long descending trill with a slightly musical quality, and a harsh growling call. Patchy distribution from Costa Rica to southern Brazil.
识别特征
The ocellated crake is generally around 165mm long, and is sexually dimorphic in size, with males weighing roughly 40 grams and females 24 grams.<p>Its plumage consists of an overall cinnamon color on the face, breast and belly. Its wings, nape and tail are a darker brown, while the crown has more of an orange hue. Some observers have suggested that the crown color is another sexually dimorphic trait. There is also a varying degree of cream or white on the throat and underparts. The nape, back, wing coverts and rump are mottled by distinctive white spots, each surrounded by a black ring.<p>It has a red iris and its bill is yellowish-green, with some black on the upper mandible.<p>The M. s. chapmani subspecies differs slightly in size and coloration. It is larger, has paler underparts, and more orange-brown coloration rather than cinnamon. It has less of the distinctive black and white spotting, with the spotting not covering the rump or upper tail coverts. The black border around the white spots is also thinner compared to the nominate subspecies.
分类信息
The ocellated crake was initially described in Western terms by Félix de Azara in his self-published work "Apuntamientos para la historia natural de los páxaros del Paraguay y Río de la Plata" in 1802, but his works were not taken seriously at the time as they were considered to be speculative and unscientific.<p>The species was officially described by Jean Louis Cabanis and its name was dedicated to Moritz Richard Schomburgk in "Reisen in Britisch-Guiana in den Jahren 1840-1844 : nebst einer Fauna und Flora Guiana's nach Vorlagen von Johannes Müller, Ehrenberg, Erichson, Klotzsch, Troschel, Cabanis und Andern" in 1848.<p>The American Ornithological Society recently published its 64th supplement to the checklist of birds in North America. The American Ornithological Society's Committee on Classification and Nomenclature has eliminated the monotypic genus Micropygia as a result of a recent phylogenetic analysis that found that M. schomburgkii was very closely related to the Russet-crowned crake (Rufirallus viridis), and have placed the ocellated crake into this genus. The new species name would be Rufirallus schomburgkii.
- 学名
- Rufirallus schomburgkii
- 命名信息
- (Schomburgk, 1848)
- 目
- Gruiformes
- 科
- Rallidae
- 属
- Rufirallus
分布与栖息地
The ocellated crake has a very scattered distribution, and is found primarily in South America, but the northern edge of its range extends into Central America. It is found in Costa Rica, Colombia, Venezuela, Paraguay, Brazil, Bolivia, Peru, Suriname, French Guiana and Guyana. A population was also recently found to inhabit Argentina.<p>The known distribution of the ocellated crake has been expanding in recent years, in part because in the past its vocalizations have been difficult to distinguish from other closely-related species of rails including those of the Laterallus and Anurolimnas genera.<p>Rails are notoriously difficult to observe due to their small size and difficult to access habitat, so they are easier to identify through their trills, which are their most distinctive type of vocalization. Increasing recognition of the trill, along with more access to recordings and the ability to use the playback technique have made the species easier to detect, leading to a more comprehensive distribution.<p>The ocellated crake is found in open grassland and savanna habitats, generally densely-packed and tall grasses of one meter or more. It can be found in either dryer, well-drained habitats or wetter, flooded ones, and is observed more frequently in dry habitats. These grasslands are generally successional habitats that form as a result of major disturbances to an area, either as a result of anthropogenic activity or naturally-occurring disturbances, primarily wildfires.<p>The composition of grass species in their habitat varies by region. For example, in central and southeastern Brazil, it is found in dry grasslands dominated by the Tristachya leiostachya grass species. In its range in Argentina, the ocellated crake was observed in drier grasslands where the dominant grasses were Sandysoil Indiangrass (Sorghastrum setosum) and Little Bluestem (Schizachyrium microstachyum).<p>They can be found in habitats reaching as high as 1700 meters above sea level.
- 迁徙
- Resident species
行为
Migration pattern: Resident species.
保护状况
Population trend: declining.
- 种群趋势
- declining
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