Eggs of the ‘lost’ Slender-billed Curlew Numenius tenuirostris

Summary. Slender-billed Curlew Numenius tenuirostris is Critically Endangered and may be extinct. Its breeding biology is known exclusively from early 20th-century accounts from central Russia and Kazakhstan, and the eggs were heretofore known from a single specimen in the Manchester Museum. Here, we provide details of five additional putative Slender-billed Curlew eggs held in public and private collections. The eggs show remarkable variation in size, with two being only 85% of the mean length and breadth. Notably, one of the putative clutches was from the European side of the Ural Mountains, far to the west of the established breeding range. Molecular identification would aid in identifying additional specimens, which would be easily confused with eggs of other Numenius.