Home » Bird Taxonomy » Phylogenetic position of the Slender-billed Curlew

DNA confirms Slender-billed Curlew is a valid species

The mitochondrial genome of the presumably extinct Slender-billed Curlew is sequenced for the first time. This confirmed that the species is genetically distinct from the related curlews.

The only known video of Slender-billed Curlew, recorded at Merja Zerga, Morocco, in January 1994 by Andy Butler.

The Slender-billed Curlew (Numenius tenuirostris) is one of the rarest bird species in the Palearctic region. Despite its rarity, it’s still officially categorized as a “Critically Endangered” species (i.e. not declared as extinct).

The last verified sightings of the Slender-billed Curlew were at Merja Zerga Lagoon, Morocco, in 1995. Subsequent sightings of the species, including those in Greece (1999), Oman (1999) and Hungary (2001), have not been widely accepted. In any case, Merja Zerga is the best known wintering site of the species and the sightings there were well-documented by both conservationists and amateur birders in the 1980s and early 1990s.

If the wintering and stopover areas of the Slender-billed Curlew are known, we can’t say so for its breeding grounds. The only known nesting area (where a few nests were found, all before 1924) is located near Omsk, south-western Siberia. However, a new study using stable isotopes from museum specimens found that this site may actually be at the edge of the species’ breeding range. In fact, this study revealed that the main area is/was further south in the steppes of northern Kazakhstan. More about this study is this BOU blog: “Chasing isotope ‘ghosts’ – Where do Slender-billed Curlews breed?”.

Slender-billed Curlew (Numenius tenuirostris), Merja Zerga, Morocco, winter 1995 (Chris Gomersall)
Slender-billed Curlew (Numenius tenuirostris), Merja Zerga, Morocco, winter 1995 (Chris Gomersall).

Phylogenetic relationship with the other curlews

Although the species status of the Slender-billed Curlew has probably never been doubted, its position in the phylogenetic tree has been based only on morphological characters. Currently the species is generally placed in the taxonomic lists between the Far Eastern Curlew (N. madagascariensis) and the Eurasian Curlew (N. arquata). There are, however, some deviations from this “consensus”.

The mitochondrial DNA (mtDNA) of the Slender-billed Curlew was sequenced and published for the first time in a recent paper by Sharko and his coauthors. The mtDNA was obtained from the skin and feathers of an individual collected in Crimea in 1855. The study showed that the Slender-billed Curlew is indeed distinct and its closest relative is the Eurasian Curlew. The clade formed by these two species is sister to the Far Eastern Curlew.

There are many examples where morphology is not concordant with true phylogeny (e.g. West African Crested Tern), in this case however the two agreed almost perfectly.


Sharko, F. S., Boulygina, E. S., Rastorguev, S. M., Tsygankova, S. V., Tomkovich, P. S. & Nedoluzhko, A. V. 2019. Phylogenetic position of the presumably extinct slender-billed curlew, Numenius tenuirostris. Mitochondrial DNA Part A 30: 626-631.

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