Chionis – Sheathbills

Sheathbills are often compared to pigeons in size and appearance but distinct in their ecological niches and behaviors. This small family of birds includes only two species, the Snowy sheathbill (Chionis albus) and the Black-faced sheathbill (Chionis minor), which reside in the stark and challenging environments of the sub-Antarctic and Antarctic regions.

Sheathbills are predominantly white birds, a feature that provides them with camouflage against the snowy and icy landscapes they inhabit. Their legs are short and strong, well-suited to their mostly terrestrial lifestyle, and their feet are unwebbed, differing from most other birds found in similar locales. This lack of webbing is an adaptation to their non-aquatic feeding habits, as they forage on land rather than in water.

One of the most distinctive features of sheathbills is their sturdy bill, which is enveloped by a horny sheath. This adaptation gives them a robust tool for foraging and feeding. The bill’s coloring varies between species, from entirely black to a combination of yellow and black. The cheeks of these birds are devoid of feathers and display a wattle, which can be a sign of their health and vitality, often used in communication and display during the breeding season.

Another unusual feature of sheathbills is the sharp spike located on the carpal joint of their wings. While not used for predation, these spikes can serve as a defensive weapon against threats or in disputes over territory and mates.

Sheathbills are highly adapted to the extreme conditions of their habitats. They breed on subantarctic islands and the Antarctic Peninsula, where they nest in rocky crevices or burrows, often returning to the same site year after year. During the austral winter, some populations migrate northward to the Falkland Islands and the southern coasts of South America.