The Slender-billed curlew (Numenius tenuirostris), a migratory shorebird that is estimated to have declined to less than 50 individuals, is a medium-sized wader, one of the six curlews of the same genus living in the world. It remains a bird whose ecology and biology (food habits, breeding behaviour, etc) are still unknown. After the completion of the breeding period in Northwest Siberia, the Slender-billed curlew migrates over a distance of 5-6,500 km crossing Southeast Russia and Southeast Europe to its overwintering grounds in Morocco and along the Persian Gulf.
Under the Convention on Migratory Species (CMS) the Slender-billed curlew Memorandum of Understanding (MoU) was concluded became effective on 10 September 1994. It aims to safeguard this highly threatened species and is signed by 19 of the 30 range states as well as the CIC and BirdLife International.