Polluela Negra

Identificación

The black rail is a small black bird with a short bill. Black rails usually weigh 29-39 g, are 10-15 cm in length, and have a wingspan of 8.7-11.0 in (22-28 cm). The body is dark, with white speckles along the back and wings. Both the beak and legs are dark. Adults have a red eye that appears around 3 months of age.<p>It will often make its presence known by its voice. In North America, it has a distinctive ki-ki-krr call or an aggressive, presumably territorial, growl. This is primarily uttered during the night, when these birds are most vocal. The peak of vocalization is during the first two weeks of May, when breeding and courtship behaviors are also at their peak. The South American subspecies have a quite different voice.

Taxonomía

The black rail was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it with all the rails in the genus Rallus and coined the binomial name Rallus jamaicensis. Gmelin based his description on the "Least water hen" that had been described and illustrated in 1760 by the English naturalist George Edwards in his Gleanings of Natural History. Edwards had obtained a preserved specimen that had been brought to London from Jamaica by Patrick Browne. Browne had briefly mentioned the rail in his book "The Civil and Natural History of Jamaica". The black rail is now placed with 12 other small rails and crakes in the genus Laterallus that was introduced in 1855 by George Robert Gray. The genus name is a portmanteau of Rallus lateralis, a synonym of the binomial name for the rufous-sided crake, the type species of the genus. The specific epithet jamaicensis is from "Jamaica", the type locality.<p>There are five recognized subspecies:<p>Their taxonomy is in need of a review. Especially the Junin rail has a distinctive plumage and is often considered a separate species (rather than a subspecies of the black rail), but its voice, while showing some differences, generally resembles that of the two other South American subspecies, L. j. murivagans and L. j. salinasi. However, their voices are quite distinct from the voices of black rails of North America. Preliminary evidence also suggests that the Galapagos crake, another member of the black rail species complex, has a voice that resembles that of the South American black rails. Genetic data is lacking for most members of the complex, except the Galapagos crake which diverged from the North American black rail about 1.2 million years ago.

Nombre científico

Laterallus jamaicensis

Autoridad

(Gmelin, JF, 1789)

Orden

Gruiformes

Familia

Rallidae

Género

Laterallus

Distribución y hábitat

It is found in scattered parts of North America, the Caribbean, and South America, usually in coastal salt marshes but also in some freshwater marshes. The most suitable habitat to find the Black Rail is within the high marshes The high marsh provides an ideal environment for the Black Rail, as it spends most of its time concealed within the vegetation found in this area. The bird's unique habitat choice is primarily driven by its foraging habits. While the Black Rail stays in the drier areas of the marsh, it strategically selects locations adjacent to the low marsh regions that experience occasional inundation during spring tides. These wetter parts of the marsh serve as essential foraging grounds where the Black Rail can find mud-dwelling invertebrates. The dry areas provide safe spaces for nesting by protecting their nests from flooding during high tide. The high marsh habitat is characterized by large stretches of grasses interspersed with patches of open salt panne. The salt panne is typically dry for the majority of the year but experiences periodic flooding during extreme spring tides. In the Florida Gulf Coast marshes, one of the most common grass species in the high marsh is the marsh-hay cordgrass, which is favored by the Black Rail. It is extinct or threatened in many locations due to habitat loss. The largest populations in North America are in Florida and California.

Migración

Complete migrants

Comportamiento

The black rail is rarely seen and prefers running in the cover of the dense marsh vegetation to flying.<p>This rail is territorial during the breeding season, and occasionally males will mate with two or more females. The nests of this bird are placed on the ground, in dense, swampy vegetation or in patches of flooded grass. The nests are bowl-shaped and built with vegetation loosely woven.<p>The clutch of this bird usually consists of six to eight creamy white speckled, with reddish-brown spots, eggs. These eggs are roundish and measure around 23 by 17 millimetres (0.91 by 0.67 in). They are incubated by both parents, taking shifts of approximately one hour each, for 16 to 20 days. The precocial young then hatch.<p>In 2015, the first ever breeding by black rails in South Carolina was captured through a  camera study. This species was once thought to be a non-breeding visitor to the state.<p>The black rail is an opportunistic feeder and consumes a wide range of food. Its diet includes seeds, insects, crustaceans and mollusks. The black rail forages by feeding along the water lines after high and low tide.<p>Under the IUCN Red List, the black rail is listed as endangered with decreasing populations. The IUCN estimates there are between 28,000 and  92,000 mature individuals remaining. The largest threats to the Black Rail are habitat destruction and severe weather events.<p>The wetland habitat that the black rail depends on has steadily declined through the last several decades, due to draining for development and conversion to agricultural land.  <p>In addition to declining populations and increasing threats, the black rail is also impacted by the lack of scientific studies available. Because of the secretive and hard to observe nature of the bird, there is very little known about them to help prevent population decline.  <p>They are preyed upon by many avian (hawks, egrets, and herons) and mammalian (foxes and cats) predators, and rely on the cover of thick marsh vegetation for protection. High tides are a dangerous time for black rails, as they are quite vulnerable to predation outside the marsh.

Conservación

Tendencia poblacional

declining