Zapata Rail, Cyanolimnas cerverai

The Zapata Rail is the only member of the monotypic genus Cyanolimnus. It is overall a dark-colored rail bird. It has grayish-blue underparts, a red-based yellow bill, brown upperparts, white under tail coverts, and red eyes and legs. Their short wings make it almost unable to fly. It is endemic to the wetlands of the Zapata Peninsula in southern Cuba, where its only known nest was discovered in saw grass tussocks. There is not much known about its diet or its reproductive behavior, and its described calls may belong to a different species.

This bird was discovered a Spanish zoologist Fermin Zanon Cervera in March 1927 in the Zapata Swamp near Santo Tomas, in the southern Matanzas Province of Cuba. The swamp is a home to one other bird that is found nowhere else, the Zapata Wren and also gives its name to the Zapata Sparrow. Due to constant habitat loss in its limited range, its tiny population size, and predation by introduced mammals at catfish, the Zapata Rail is appraised as critically endangered on the IUCN Red List of threatened species. Tourism and changing climates might cause threats in the future.

The description of this bird is it medium sized, dark rail, about 11.4 inches long. The forehead, head sides and underparts are slate grey with some minor barring on the lower belly. The upperparts are olive brown, the flanks are grey-brown and the under tail is white. The iris, legs, and feet are red, and the bill is yellow with a red base. The tail feathers are only sparingly barred. It has very short, rounded wings. Both sexes are similar in appearance, but the young, immature birds are a duller color and have olive feet and bill. The chicks, as with all rails, are covered with blackish down. The Zapata Rails call is depicted as a bouncing cutucutu-cutucutu-cutucutu, much like that of a Bare-Legged Owl and a loud Limpkin-like kuvk kuck. However, those calls might actually be those of the Spotted Rail.

This bird was previously portrayed by American herpetologist Thomas Barbour and his compatriot, ornithologist James Lee Peters in 1927. They rendered it special enough for its own genus, Cyanolimnus. The genus name comes from Ancient Greek kuanos “dark blue” and Modern Latin limnus “rail or crake”; the specific name cerverai honors its discoverer, Fermin Zanon Cervera. He was a Spanish soldier who had stayed on after the Spanish-American war and became a professional naturalist.

Thomas Barbour had been accompanied by Cervera on his previous visits to Cuba, and upon hearing of the strange birds to be found in the Zapata area, he sent Cervera on a series of trips into the region. Cervera eventually found the rail near the very small settlement which is memorialized in the Spanish name for the rail, “Gallinuela de Santo Tomas”. Cervera also discovered the Zapata Wren and the Zapata Sparrow, and his name is being honored by the new ecological center in the Cienago de Zapata National Park.

The rail family contains more than 150 species that are divided into at least 50 classes. The Zapata Rail is the only member of the genus Cyanolimnus. It is deemed intermediate between two other New World genera, Neocrex and Pardirallus. All of the six species in the genera are long-billed. Five of them have drab tail colors, and all but one of them have a red spot at the base of their bill. They are believed to have descended from Amauromas-like ancestral stock.

The preferential spot for this bird is flooded vegetation (60 to 80 inches tall). This consists of tangled, bush-covered swamp and low trees, and preferably near higher ground. It’s a Cuban endemic limited to the northern parts of the Zapata swamp, which happens to be the only location for the Zapata Wren and the nominate subspecies of the Zapata Sparrow. Standard plants of the swamp include wax-myrtle, the willow Salix long pipes, the saw grass Cladium jamaicensis, and the narrow leaf cattail.

It was once more widespread, with its fossilized bones found at Havana, Pinar del Rio and the Isla de la Juventud. Thomas Barbour didn’t believe that the rail, the Zapata Sparrow, and wren were remnants in the sense that they once upon a time ranged broadly over Cuba, since the birds were so extremely adapted to the swamps. He judged that locations similar to those found today perhaps once have existed over the large submerged area now characterized by the shallow banks, with scattered mangrove keys, which stretch towards the Isla de la Juventud and maybe eastward along the southern Cuban coast. The fossilized birds at Isla de la Juventud are much like the single extant specimen, but the rarity of available resources makes it almost impossible to determine whether the populations were genuinely different.

They usually breed in Cladium jamaicensis they built the nest above water-level on a raised tussock. The breeding process usually occurs around September and possibly in December and January. James Bond, and American ornithologist, discovered a nest containing three white eggs two feet above water level in saw grass, but not much else is known about the breeding biology. The rails are genuinely monogamous, and all have precocial chicks which are fed and guarded by the adults. These birds prefer to eat in saw grass. Although the diet is not recorded, most marsh rails are omnivorous, feeding on invertebrates and plant material. The rails might disperse in the rainy season, returning to permanently flooded areas in the dry months.

Like other rails, they are very difficult to observe as it moves through the saw grass, and may crouch to deter detection. When disturbed, they may run a short distance and then stop, raising its tail with the conspicuous white under tail showing. Even though it has short wings, the Zapata Rail may not be all that flightless. On morphological grounds, it would be classified as a flightless species, since the pectoral girdle and wing are as reduced as in other species of rails that are thought to be flightless, but Bond testified that he saw one flutter about ten feet across a canal.

The Zapata Rail is restricted to a single area, and its tiny population, estimated on the basis of recent surveys and local assessments of population densities at between 250-1000 individuals, judged as decreasing. In the past, grass cutting for roof thatch was a source of widespread loss of breeding habit, and habitat loss through dry season burning of the vegetation continues. Introducing new predators such as the Small Asian Mongoose and the more recent African Sharptooth Catfish has become a problem. Clarias gariepinus has been acknowledged as a major predator of rail chicks.

It appears to have been easily found in the Santo Tomas area until 1931, but there were no further records until the 1970s when birds were seen 40 miles away at Laguna del Tesoro. The few records in following years suggest that population numbers have remained low, although after no official sightings of them for two decades, a survey in 1998 found the birds at two new locations in the Zapata Swamp. In Peralta, ten rails were detected, and then seven at Hata de Jicarita. On the base of this sample it was estimated that 70 to 90 rails were present in the 230 hectares (570 acres) between the two sites.

Island species of rails are predominantly vulnerable to population loss because they habitually and swiftly evolve to become flightless or very weak fliers, and are very subject to introduced predators. Fifteen species have become extinct since 1600, and more than 30 are endangered.

This bird was classified as an endangered species on the IUCN Red List until 2011, when its status was uplisted to critically endangered. This had already been suggested, given the lack of knowledge of its bird calls, the numbers may be lower than currently estimated. There are two remaining sites in protected areas, the Corral de Santo Tomas Faunal Refuge, and the Laguna del Tesoro nature tourism area. Recently conducted surveys throughout the species’ range projected conservation measures including the control of dry season burning.

There is plans encouraging more tourists to visit the Zapata area, especially from Europe, and if the United States lets its citizens to visit Cuba in the future, this could increase the effects of ecotourism. Although this could dangerously impact the wetland, Cuba’s Tourism Minister, Manuel Marrero, and Pablo Bouza, the Cienaga de Zapata National Park director, both stated that the increase in tourism would be sustainable. For the long-term, the Ramsar-listed swamp itself may be threatened. The rising sea levels caused by global warming could contaminate the wetland with saltwater, damaging the plants and fauna, and by the year 2100 the area of Cienaga de Zapata would be decreased by 1/5th. Increased ocean temperatures caused by climate change could also produce stronger hurricanes and drought. Bouza warned that the fallen vegetation left behind from hurricanes could act as fuel for further damaging fires once it had dried out.

Image Caption: Zapata Rail (Cyanolimnas cerverai) in the collection of the Museo Felipe Poey. Credit: Birdingcuba64/Wikipedia (CC BY-SA 3.0)