Rails, or Rallidae, are a diverse family of small to medium-sized birds found worldwide, except for Antarctica, deserts, polar regions, and high mountains. This family includes species like crakes, coots, and gallinules, many of which favor wetlands but can be found in various terrestrial habitats. Rails have evolved a remarkable range, from 12 to 63 cm in length, with some species having markedly long necks and laterally compressed bodies. Their bills are particularly varied, some being considerably long, while others are short and broad, and a few species feature a significant frontal shield.
These birds generally have limited sexual size dimorphism and their calls are often loud, aiding communication through dense vegetation. Rails typically exhibit short, rounded wings and although they're not powerful fliers, many can sustain long flights during migration. However, their flight is so weak that it easily leads them off course, which is why they're often found on isolated islands. This propensity for weak flight and even flightlessness is a classic example of parallel evolution, particularly abundant on islands where lack of predators renders the ability to fly unnecessary.
Flightless birds tend to have fewer energy requirements, and this has allowed for the diversification and adaptation of rails to various ecological niches on islands. Unfortunately, many island rail species have gone extinct or are endangered due to human activity and introduction of predators.
Rails typically have a diet that includes invertebrates, fruit, or seedlings, and they are often shy and secretive birds that prefer dense vegetation near water bodies. They usually lay five to 10 eggs, are most often monogamous, and sometimes experience polygyny and polyandry.
Humans have hunted rails for their meat and eggs, and some species like the Guam rail have suffered greatly from introduced species. Conservation efforts continue to try and save those that are endangered. The classification of rails, as evidenced by genetic studies, places them within the larger order of Gruiformes or, in some cases, their own order of Ralliformes. The family is scientifically recognized as having been described by Constantine Samuel Rafinesque in 1815 and contains numerous genera and species, with a rich fossil record extending into the Eocene. Some species and genera have recently become extinct due to human impact.
Overall, the Rallidae family is characterized by their adaptability and the remarkable cases of flightlessness seen among island species. Conservation efforts remain crucial to protect the existing diversity within this family of birds.