Slender-billed curlew

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Slender-billed curlew

Critically Endangered  (IUCN 3.1)[1]
CITES Appendix I (CITES)[2]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Charadriiformes
Family: Scolopacidae
Genus: Numenius
Species:
N. tenuirostris
Binomial name
Numenius tenuirostris
Vieillot, 1817
Range of N. tenuirostris
  Breeding
  Non-breeding
  Probably extinct

The slender-billed curlew (Numenius tenuirostris) is a

Mediterranean. This species has occurred as a vagrant in western Europe, the Canary Islands, the Azores, Oman, Canada, and Japan. The slender-billed curlew was always a rare species and is feared extinct, with the last verifiable sighting being in 2004.[3]

Description

Henrik Grönvold

The slender-billed curlew is a small curlew, 36–41 cm (14–16 in) in length with a 77–88 cm (30–35 in) wingspan. It is therefore about the same size as a Eurasian whimbrel, but it is more like the Eurasian curlew in plumage. The breeding adult is mainly greyish brown above, with a whitish rump and lower back. The underparts are whitish, heavily streaked with dark brown. The flanks have round or heart-shaped spots. The non-breeding plumage is similar, but with fewer flank spots. Male and female are alike in plumage, but females are longer-billed than males, an adaptation in curlew species that eliminates direct competition for food between the sexes. The juvenile plumage is very similar to the adult, but the flank are marked with brown streaking, the heart-shaped spots only appearing toward the end of the first winter.

Compared to the Eurasian curlew, the slender-billed curlew is whiter on the breast, tail, and underwing, and the bill is shorter, more slender, and slightly straighter at the base. The arrowhead-shaped flank spots of the Eurasian curlew also are different from the round or heart-shaped spots of the adults slender-billed. The head pattern, with a dark cap and whitish supercilium, recalls that of the whimbrel, but that species also has a central crown stripe and a more clearly marked pattern overall; the pattern of the slender-billed curlew would be hard to make out in the field.

This species shows more white than other curlews; however, the white underwing has been stressed too much as a relevant identification criteria along with the distinctive flank markings of adults (not helpful in juvenile and 1st year bird before post-juvenile moult). The most recent and most updated identification's paper, reports as clinching characters the uniformly dark underside of 4 to 6 outer primaries (the wing-tip or "hand"), the black (adults) or anyway daker (juvenile and 1st y bird) legs, and the white tail with fewer dark bars (Corso et al., 2014).

Vocalisations

The call is a cour-lee, similar to that of the Eurasian curlew, but higher-pitched, more melodic, and shorter. The alarm call is a fast cu-ee.

Distribution

The slender-billed curlew was only known to breed in a small region north of Omsk, Russia in a period between 1909 and 1925. In recent history, it mostly migrated to the Mediterranean as well as southern Arabia, with claims in the northern reaches of the Persian gulf, in

Malaga, Spain.[5]

Behaviour

Slender-billed curlew (centre) between Eurasian whimbrels

Little is known about the breeding biology, but on average the few nests observed had four eggs.

Slender-billed curlews feed by using their bills to probe soft mud for small invertebrates, but will also pick other small items off the surface if the opportunity arises. It used to be highly gregarious outside the breeding season, associating with related species, particularly Eurasian curlews.

Status

Specimen

After a long period of steady decline, the slender-billed curlew is extremely rare, with only a minute and still declining population. This is thought to be fewer than 50 adult birds, with the last verified sighting in 2004. As a result, it is now listed as

critically endangered
. However, for most specialists of the species, it is most probably extinct now (Corso et al., 2014; Kirwan et al., 2015). Indeed, all records, away from the famous ones from Morocco, from 1990 until today are not considered reliable and acceptable on stricter criteria.

The primary cause of the decline is thought to be excessive

recessive alleles and consequently with a high MVP. Furthermore, there is evidence that birds in winter quarters were more numerous once, and in general not a very rare sight in Western Europe in the nineteenth century, where they were hunted with some regularity. Later on they were additionally threatened by pollution, e.g. oil spills
. There are no data about how these threats endanger the species today. Theoretically, they might have retreated to all but inaccessible areas, but then, a single hunter or fox might unwittingly wipe out enough of the few remaining birds to doom the species.

The last well-documented nest was found in 1924, near Tara in Omsk oblast, Siberia (57°N 74°E / 57°N 74°E / 57; 74).[6] Its nesting grounds since then remain unknown, despite several intensive searches (not surprising, with more than 100,000 square kilometres to search). The extent of its decline also is reflected in the absence of wintering birds at previously regular Moroccan sites.

More recently, 20 birds were recorded in

the Druridge Bay curlew. The bird was initially accepted onto the British List[7] but was removed in 2013 following a review of the identification.[8]

Slender-billed curlews have been reported in various Western

Palearctic locations on a number of occasions since the Druridge bird, including claimed, but unverified, sightings of single birds from Italy and Greece; none have been documented with conclusive photographs and at least one claimed bird, at RSPB Minsmere, Suffolk
, England, in 2004, is now widely believed to have been a Eurasian curlew.

Illustration from ca 1830

Further sourced reports of the species were published in 2007, in British Birds magazine;[9] the article stated, quoting from Zhmud:[10]

During the last few years, small groups of birds have been found in the northern coastal areas [of the

Common Glasswort
Salicornia europaea [...] Four birds were present from 25 July to 21 August 2003, six were seen on 11 August 2004, and another on 12 August 2004.

A sighting of a single bird was reported from Albania in 2006 by a team including ornithologists from the environmental organization EuroNatur.

Thus, although hard proof is lacking, but given the extent of possible habitat and the

subpopulation
.

References

General references

  • Hayman, Peter; Marchant, John & Prater, Tony (1986). Shorebirds: an identification guide to the waders of the world. Houghton Mifflin, Boston.
    ISBN 0-395-60237-8
  • Svensson, Lars; Zetterström, Dan; Mullarney, Killian & Grant, P. J. (1999). Collins bird guide. Harper & Collins, London.
    ISBN 0-00-219728-6
  • Corso, Andrea; Jansen, Justin; Kokay, Szabolcs (2014). "A review of the identification criteria and variability of the Slender-billed Curlew." British Bird 107: 339–370. https://www.researchgate.net/publication/269160426_A_review_of_the_identification_criteria_and_variability_of_the_Slender-billed_Curlew

Identification

Corso, Andrea; Jansen, Justin; Kokay, Szabolcs (2014). "A review of the identification criteria and variability of the Slender-billed Curlew." British Bird 107: 339–370. https://www.researchgate.net/publication/269160426_A_review_of_the_identification_criteria_and_variability_of_the_Slender-billed_Curlew

  • Identification of Slender-billed Curlew, John Marchant, British Birds 77: 135–140.
  • Slender-billed Curlew studies, Richard Porter, British Birds 77: 581–586.
  • Habitat of Slender-billed Curlews in Morocco, Arnoud van den Berg, British Birds 83: 1–7.
  • Slender-billed Curlew in Tunisia in Feb 1984, Eddy Wijmengs & Klaas van Dijk, Dutch Birding 7: 67–68.
  • Slender-billed Curlews in Morocco in Feb 1979, Peter Ewins, Dutch Birding 11: 119–120.
  • Identification of Slender-billed Curlew and its occurrence in Morocco in winter 1987/88, Arnoud van den Berg, Dutch Birding 10: 45–53.
  • Slender-billed Curlew on Sicily in March 1996, Andrea Corso, Dutch Birding 18: 302.
  • Slender-billed Curlew collected at Canis-vliet in September 1896, Gunter De Smet, Dutch Birding 19: 230–232.
  • The identification of the Slender-billed Curlew, British Birds Vol 56 No8 1963
  • Kirwan, Guy; Porter, Richard; Scott, Derek (2015). Chronicle of an extinction? A review of Slender-billed Curlew records in the Middle East. "British Birds" 108: 669–682.

Specific references

  1. doi:10.2305/IUCN.UK.2018-2.RLTS.T22693185A131111201.en
    . Retrieved 13 November 2021.
  2. ^ "Appendices | CITES". cites.org. Retrieved 14 January 2022.
  3. ^ "magornitho".
  4. ^ "Slender billed curlew=10 November 2022". birdlife.
  5. ^ "Ornithology of Gibraltar, page 290=10 November 2022". openlibrary.
  6. ^ Gretton, Adam; Yurlov, Alexander K. & Boere, Gerard C. (2002). Where does the Slender-billed Curlew nest, and what future does it have?
    ISSN 0007-0335 HTML abstract
  7. ^ Cleeves, Tim (2002). Slender-billed Curlew in Northumberland: new to Britain and Ireland.
    ISSN 0007-0335 HTML abstract
  8. ^ BOU (2013). "Changes to the British List". Retrieved 5 December 2013.
  9. ^ Goriup, Paul; Baboianu, Grigore & Chernichko, Joseph (2007). The Danube Delta: Europe's remarkable wetland
    ISSN 0007-0335
  10. ^ Zhmud, M. 2005. "Slender-billed Curlew: promising discovery in the Danube delta." Wader Study Group Bull. 106: 51–54

External links

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