slender-billed curlew

slender-billed curlew, (Numenius tenuirostris), wide-ranging migratory shorebird once found in wetlands, grasslands, and intertidal areas on three continents. During the 20th century, the species inhabited Eurasia and Africa, likely migrating from breeding areas located in Central Asia to winter along the coast of northwestern Africa, the Nile River delta, the Tigris and Euphrates delta, and Yemen. The last confirmed sighting of the slender-billed curlew took place in Morocco on 1995, and the species was declared extinct in 2024.

Natural history

Compared with the common, or Eurasian, curlew (N. arquata) and the eastern curlew (N. madagascariensis), both of which grow to be nearly 60 cm (24 inches) long, the slender-billed curlew was substantially smaller. Adult slender-billed curlews measured 36 to 41 cm (14 to 16 inches) long, weighed between 255 and 360 grams (9 and 13 ounces), and had a wingspan that ranged from 77 to 88 cm (30 to 35 inches) wide. Although there were few size and plumage differences between males and females, females possessed longer bills. Adults were mostly white, with large concentrations of grayish brown and gray streaks and spots that covered their heads and wings and extended along their backs. Some of the white feathers on their undersides were accented with small, dark, heart-shaped spots. Juvenile feather coloration and patterning resembled that of adults in most respects; however, they lacked the heart-shaped spots.

Surprisingly little is known about their ecology. Given their long bills, however, they are thought to have consumed invertebrates, such as crustaceans, insects, and earthworms. Slender-billed curlews were nesting birds that likely bred in bog-forest transition zones. The last confirmed slender-billed curlew nesting site was documented in Siberia early in the 20th century. The results of a DNA study published in 2017 suggest that the species’ breeding area could have occurred in the steppes of present-day northern Kazakhstan and southern Russia. Although the slender-billed curlew likely had natural predators, none are known. The species, however, was hunted extensively by people during the 20th century.

Conservation status

The results of a population modeling study published in 2024 placed the probability of the slender-billed curlew’s extinction at 96 percent. The study also suggested that the bird likely died out before 2022. This information—combined with the lack of confirmed sightings of the bird since the 1990s—led several conservation organizations, including the Royal Society for the Protection of Birds, BirdLife International, Naturalis, and the Natural History Museum in London, to formally declare the species extinct. The International Union for Conservation of Nature and Natural Resources (IUCN), which is the final arbiter on this matter, has yet to reassess the slender-billed curlew and thus continues to classify the bird as a critically endangered species. The IUCN first applied this status to the species in 1994 because of population declines stemming from hunting and habitat loss. The IUCN and other sources also note that much of the slender-billed curlew’s habitat declined during the 20th century because of habitat loss related to the systematic draining of wetlands and the conversion of steppes for agriculture.