Rails

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Rails

Rails are small, shy, marshland birds in the family Rallidae, which includes about 134 species. This family has a worldwide distribution, occurring on all continents except Antarctica. Many species of rails occur only on certain remote, oceanic islands, where many of these isolated species have evolved a flightless condition because of the lack of predators. Unfortunately, this characteristic makes these birds extremely vulnerable to predators that were subsequently introduced by humans to the remote habitats of these flightless birds. Consequently, many of the island species are now extinct or endangered.

Biology of rails

Species in the rail family have a rather wide range of body and bill shapes. The true rails have a rather long, slender beak, often downward curving. The body of rails that live in marsh habitats is quite compressed laterally, a characteristic that gave rise to the saying, “skinny as a rail.” Species that are commonly called rails generally live in reedy marshes, and are relatively large birds with a beak, legs, and toes that are long. Crakes are relatively small birds with stubby, chicken-like bills. Coots are duck-like, aquatic birds with lobed feet used for swimming and diving, and usually a stubby bill, although it can be massive in certain species. Gallinules or moorhens are coot-like in shape, but they have long toes that help with walking on floating aquatic vegetation.

Most species in the rail family have a subdued coloration of brown, black, and white. However, gallinules are often very colorful birds, some species being a bright, sometimes iridescent green, purple, or turquoise, usually with a red beak.

Rails eat many types of animal foods, including a wide range of invertebrates, and sometimes fish and amphibians. Most rails also eat many types of aquatic plants, and some species are exclusively plant eaters. Most species of rails build their nests as mounds of vegetation, in which they lay up to 12 eggs. Newly hatched rails are precocial, which means they are capable of leaving the nest almost as soon as they hatch, following their parents as they search for food.

Rails of North America

Nine species in the rail family occur regularly in North America, primarily in wetland habitats. The American coot (Fulica americana) is widespread and common in marshes and other relatively productive wetlands. This species has a gray body and white beak, with a vividly red frontal lobe at the top of the upper mandible, and red-colored eyes. This species chiefly feeds on aquatic vegetation, which it sometimes obtains by diving. Coots can be raucously aggressive to each other, and to other species of aquatic birds. The common gallinule or moorhen (Gallinula chloropus) occurs in marshes of the eastern United States, while the purple gallinule (Porphyrula martinica) is largely restricted to parts of Florida and Louisiana.

Some other less aquatic species of rails can also be fairly common in suitable habitats. However, these birds are very cryptic and tend to hide well in their habitat of tall, reedy marshes, so they are not often seen. One of these elusive species is the sora (Porzana carolina), the whistled calls and whinnies of which are more often heard than the birds are seen. The Virginia rail (Rallus limicola) is another, relatively common but evasive rail of marshes. The largest rail in North America is the king rail (R. elegans), with a body length of 14 in (36 cm). It is found in marshes in the eastern United States. The clapper rail (Rallus long-irostris) is slightly smaller at 12 in (30 cm), and is restricted to brackish and salt marshes.

Conservation of rails

Many species of rails that live on remote, oceanic islands have become flightless, because of the lack of natural predators. This is true of various endemic species that are specific to particular islands (that is, they do not occur anywhere else), and also of flightless populations of more wide-ranging species of rails. The benefit of flightlessness to rails living on islands is not totally clear, but some ornithologists have speculated that this trait might have something to do with the conservation of energy, coupled with an absence of predators.

Unfortunately, flightless rails are extremely vulnerable to suffering debilitating population declines when humans introduce predators to their isolated habitats. Most commonly, these catastrophes involve accidental introductions of rats, or deliberate introductions of pigs or cats. At least 15 endemic species of island rails are known to have become extinct, largely as a result of introduced predators. Numerous other island rails still survive, but are endangered.

However, the real number of extinctions is undoubtedly much larger than this. Some ornithologists have speculated that each of the approximately 800 islands inhabited by Polynesians in the Pacific Ocean may have had one or several endemic species in the rail family, as well as other unique species of birds. Most of these rare and endemic species became extinct in prehistoric times, soon after the islands were discovered and colonized by prehistoric Polynesians. These extinctions occurred as a result of predation by introduced rats, overhunting by humans, and to a lesser degree, losses of habitat.

Various species in the rail family have been hunted more recently for meat or sport. Today, however, this is a less common practice than it used to be. Some species of gallinules are sometimes considered to be pests of aquatic crops, such as rice, and they may be hunted to reduce that sort of agricultural damage. However, this is a relatively unusual circumstance.

Because rails are generally species of wetlands, their populations are greatly threatened by losses of that type of habitat. Wetlands are disappearing or being otherwise degraded in most parts of the world. This is occurring as a result of infilling of wetlands to develop land for urbanization, draining for agriculture, and pollution by pesticides and fertilizers.

See also Extinction.