The St. Helena Crake or St. Helena Rail (Porzana astrictocarpus) is an extinct bird species from Saint Helena, one of two flightless rails that have survived on that island until the early 16th. centuryCentury.
After American ornithologist Alexander Wetmore described bones of the large St. Helena Swamphen (Atlantisia podarces) from Prosperous Bay, Saint Helena, in 1963, American paleontologist Storrs Olson found almost complete skeletons of the St. Helena Crake in the same region in 1973. These skeletons consist of bones that were smaller than the bones of Atlantisia podarces. Due to the peculiar shape of the carpometacarpus, Olson named this species Porzana astrictocarpus.
Olson proceeds on the assumption that the St. Helena Crake was a derivative of the Baillon’s Crake (Porzana pusilla), which is widespread in Europe and Africa. Thus, because there were no predators on St. Helena, it had lost its ability to fly. However, when St. Helena was colonised in 1502, the settlers brought a lot of mammals to the island, which sealed the fate of the St. Helena Crake.
Description
St. Helena Crake is a member of the rail family. It was known for its land habits, and in this instance, flightlessness. It was a smaller bird in terms of morphology, and much smaller than its island-sharing partner, the St. Helena Swamphen, which is also extinct ( Atlantisia Podarces). The two species coexisted on the island for many centuries and occupied different ecological niches.
The St. Helena Crake is distinguished by its smaller wings and unique skeletal structure. This includes the carpometacarpus, which is a part of the bird’s wing. Storrs L. Olson was the first to identify the bones of this species in the 1970s, based on the nearly complete skeletons that were excavated near Prosperous Bay. The bones showed a bird with a completely reduced ability to fly, which is a common evolution among birds living on islands without natural predators.
It had small, stubby wing tips and strong legs that indicated a life on the ground. The bird’s plumage, which is not known, has no preserved feathers or skins. However, it would have been earthy-toned, with browns, blacks and greys to help it blend in with the volcanic terrain of the island.
Habitat and Distribution
The St. Helena Crake is endemic to Saint Helena. It’s an island in the South Atlantic Ocean that’s 2,000 km from any continental landmass. The crake’s biology was shaped by its isolation. Flight became unavoidable without predators such as cats, snakes or large raptors. Over the millennia, evolutionary pressures have selected for enhanced mobility and reduced. The crake likely inhabited many ecosystems on the island. These ranged from lowland forests to shrublands and even volcanic rocky slopes. It was likely to be more common in humid, fern-rich habitats near springs or freshwater sources. Due to its extinction, the exact preference is speculative. It can be reconstructed by analysing the surrounding flora and sediments where fossils have been found.
Olson’s research placed the bird in Prosperous Bay’s dry, rugged region where the island’s oldest avifauna was preserved in caves and sediment deposits. Saint Helena was once covered with subtropical forest, which would have provided the crake with a variety of microhabitats that were relatively safe from predators until humans arrived.
Breeding and Nesting Behaviour
The St. Helena Crake is not known to breed or nest. However, it can be inferred by studying its relatives, such as the Baillon’s Crake Porzana pusilla, from which the Crake is thought to have evolved. Rails are generally ground nesters. The nests are usually built in dense vegetation near water or under low shrubs. They create simple cup-shaped structures from grasses or reeds.
It is probable that the St. Helena Crake also followed a similar cycle. The clutches of eggs would have probably contained between two and four eggs. Both males and females were likely to be involved in the incubation process and raising chicks. As with most rail species, the chicks would have been precocial, meaning they were covered in down when they hatched and could walk shortly after birth.
The flightless rails of islands have lower reproduction rates than their continental cousins. If this were true of the St. Helena Cra, it would have left them more vulnerable to a population collapse when predators were introduced.
Diet and Feeding Ecology
St. Helena Crakes likely foraged for invertebrates on the ground, as there were no predators to eat. It would have eaten insects, worms and snails as well as possibly small crustaceans. The short beak of this bird was likely adapted to probe into soil, leaf litter or decaying plants in search of food. Its diet may have included seeds, berries and plant material.
Crakes are opportunistic eaters, and they often feed alone or in pairs. They feed by moving slowly and deliberately through dense ground cover. Their bill is used to push aside debris or probe the soil. St. Helena Crakes, as flightless birds, would have spent the majority of their time in dense grass or on the forest floor, where there was plenty of food and hiding places. According to WWF, this species is well documented.
Communication and Vocalisation
There are no audio recordings of St. Helena Crake vocalisations, but it’s likely that they used a variety similar to other rails. The squeaky metallic or croaking sounds of these birds are used to warn off danger, establish territory or attract mates. According to Mammal Society, this species is well documented.
It is possible that the bird used vocal communication to communicate because it lived in such a densely vegetated environment. In such habitats, sound would have been more efficient than visual signals. Crakes have loud, distinctive calls that are often louder than their size, particularly during breeding season.
Status of Conservation and Extinction
The St. Helena Crake has been declared extinct. It, like many other island species and especially flightless birds, could not survive the ecological changes caused by human colonisation. Around 1502, the first humans settled on Saint Helena. They brought with them a variety of invasive species, including cats, dogs and pigs. The new predators were likely to have been attracted by the ground-nesting and flightless crake, especially the eggs and chicks.
Moreover, habitat degradation played a role. Early settlers cleared much of Saint Helena’s forest for agriculture and wood. The loss of forest would have destroyed the crake’s nesting and feeding grounds, hastening further its decline.
The St. Helena Crake is believed to have gone extinct within one century of the arrival of humans. When naturalists started formally recording species in the 18th century, the bird was already extinct. Scientists discovered subfossil remains that are the only proof of its existence.
There is a theory that the bird could have survived in remote areas of the island for a longer period, perhaps even into history. This theory is partly based on William Anderson’s 1771 description of a “bare-legged” bird in New Caledonia, which was noted by a naturalist aboard James Cook’s second voyage. Some believe that this could have been an old megapode. This is still conjecture.
Scientific Discovery and Legacy
The discovery of the crake bones in 1973 was a major milestone in the study of island fauna. Storrs L. Olson, a paleontologist, discovered nearly complete skeletons in 1973 and described the bird as a separate species because of its unique skeletal structures. The bird’s carpal bone is reflected in the name Porzana Astrictocarpus, which highlights how evolution has shaped this form.
Its appearance and physiology could be reconstructed using the fossils of scapulae and femurs. The carpometacarpus was also present. The evolutionary relationship between the Baillon’s Crake and Saint Helena suggests that they were dispersed over long distances, perhaps by storms or strong trade winds.
The extinction of St. Helena Crake provides a textbook biogeographic example, showing both the creativity of evolution and the devastation caused by ecological imbalances introduced by humans. The crake, which is now extinct, is not only studied as an example of island biogeography but also as a warning against the fragility of isolated ecosystems.
Conclusion
The story of St. Helena Crake combines fascination with sadness. The crake, like the dodo or the moa before it, is a reminder of just how quickly humans can wipe out entire species, especially those that have evolved in isolation. The flightless bird that once silently navigated the forest undergrowth on Saint Helena is no more. It has been replaced by fossilised bones, and it sends a strong message to humans about their responsibility in conserving biodiversity.
We are being called to re-examine our role as stewards as we uncover the secrets of species lost, like the St. Helena Crake. Islands with their unique ecosystems and vulnerability are particularly dependent on this kind of stewardship. This small bird’s extinction has echoed through history, warning us not to let the same thing happen again.
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