Nesotrochis: flightless island birds of the Caribbean

Nesotrochis was a genus of flightless birds known from the Greater Antilles. The named species came from Cuba, Hispaniola, Puerto Rico and the Virgin Islands, with bones recovered from caves and human food deposits. For decades, their stocky legs and reduced wings suggested a relationship to rails. Ancient mitochondrial DNA from N. steganinos instead placed the lineage close to African and Malagasy flufftails and New Zealand adzebills. The extinct bird catalogue records Nesotrochis as an island lineage whose bones and molecular evidence tell different but complementary parts of its history.

Quick facts

Species and discoveries

Alexander Wetmore named the genus Nesotrochis in 1918 for bird bones from the Virgin Islands collected by archaeologist Theodoor de Booy. The type species, N. debooyi, is represented by a right femur from a kitchen midden on St Croix. The material was later supplemented by bones from Puerto Rico. These remains put the bird in a human-used landscape, although they do not prove exactly when the last population disappeared.

Storrs Olson described N. steganinos from Hispaniola and reassessed other Caribbean rails. A Cuban fossil first named as a coot, Fulica picipicensis, was later assigned to Nesotrochis. The three names therefore reflect a history of comparison as well as separate islands. All known forms were flightless and are identified from skeletal remains rather than intact carcasses or feathers.

The genus is known from Cuba, Hispaniola, Puerto Rico and the Virgin Islands. A distribution across islands does not mean the birds moved freely among them or that every island hosted every species. Sea levels, island connections and the age of individual deposits matter, and the fossil record is uneven.

From rail-like bones to ancient DNA

Early workers placed Nesotrochis among Rallidae because its bones resembled those of rails, and the birds’ flightlessness fit a familiar pattern of island rail evolution. Olson noted distinctive anatomy, including features of the tarsometatarsus, but the deeper relationship remained uncertain. Similar locomotor adaptations can evolve independently in unrelated island birds.

In 2021, researchers recovered a nearly complete mitochondrial genome from a fossil N. steganinos. Their analysis did not place it within true rails. Instead, the lineage was sister to Sarothruridae, a group of flufftails now found in Africa, Madagascar and New Guinea, and was related to New Zealand’s extinct adzebills. The result connected Caribbean fossils to a widely dispersed gruiform history.

This is strong evidence for the sampled species, but the DNA came from N. steganinos, not every named species. Applying the same placement to the whole genus is supported by their shared anatomy and taxonomic grouping, yet additional ancient DNA could refine that picture. The study also does not identify a direct migration route or show that the modern relatives descended from the Caribbean population.

Flightlessness and island ecology

Reduced wings and robust legs indicate terrestrial locomotion. The birds were described as heavy-bodied, with expanded distal foot bones that distinguish them from many living rails. This body form is consistent with walking through dense vegetation and searching the ground, though fossils do not show their exact gait, speed or preferred cover.

“Cave rail” can be misleading. Caves preserve bones particularly well, and an owl’s discarded prey, water movement or human activity may bring remains underground. A cave locality is not evidence that the living bird regularly sheltered in darkness. Kitchen middens offer another kind of context: people collected and deposited bones, so they show contact but cannot by themselves quantify how important the bird was in diet.

Specific foods are unknown. Invertebrates, seeds and fruit are plausible for a ground-feeding island bird, but no stomach contents establish a menu. Nor do the bones preserve calls, breeding behaviour or feather colours. The most accurate reconstruction leaves these details open rather than turning modern rail behaviour into a direct observation.

Extinction and the evidence for people

Some N. debooyi bones came from pre-Columbian middens, and archaeological evidence indicates people encountered the bird. The available record does not provide a secure last date for the genus across all islands. A report of a “flightless waterhen” from Virgin Gorda has sometimes been discussed, but it cannot be confirmed as Nesotrochis from that description alone.

Human hunting may have contributed to the decline of flightless island birds. Habitat changes and introduced mammals are also possible pressures, but their timing and effects would have differed among islands. It is not possible to assign one cause to every species using the currently known bones. The fossils establish a vanished Caribbean lineage; a precise story of its final generations remains beyond them.