[order] Charadriiformes | [family] Scolopacidae | [latin] Numenius tenuirostris | [UK] Slender-Billed Curlew | [FR] Courlis ŗ bec grÍle | [DE] DŁnnschnabel-Brachvogel | [ES] Zarapito Fino | [IT] Chiurlottello | [NL] Dunbekwulp

Dunbekwulp determination

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Very pale curlew, with shortish, slim, pointed bill. White or pale buff ground color of head, neck and breast. Lower back, rump, undertail and underwing white. Uppertail coverts white with sparse brown markings. Typically has rounded or heart shaped dark markings on breast and flanks. Similar to N. phaeopus, but paler, lacks dark crown stripe. Female averages larger with longer bill. Non-breeding adult has fewer marks on flanks.

On migration a wide variety of habitats is used, including saltmarsh, steppe grassland, fishponds, saltpans and brackish lagoons. There is a similar degree of variation in the known wintering habitats, with some records from tidal mudflats (Tunisia), others from semi-desert "sebkhets" (temporary brackish wetlands in Tunisia and Algeria), and others from brackish marsh and sandy farmland (such as at Merja Zerga). In view of the species' rather broad choice of habitat on passage and in winter, it is unlikely that habitat loss in these areas has played a major part in the decline (particularly since many other wader species using the same region have not suffered such a decline). Loss of breeding-ground habitat, which may be much more specialised, would better explain such a drastic collapse. It has been argued (e.g. by Belik 1994) that the species may nest primarily in steppe areas; if so, then the massive loss of such habitat (notably in Kazakhstan) may have played a part in its decline.

Numenius tenuirostris occurs in Europe as an extremely rare passage migrant (and very occasionally as a winter visitor). The species is very poorly known, and its breeding area remains unknown. The number of verified records declined further during 1990-2000, in particular after 1995. The last flock recorded was of 19 birds wintering in Italy (1995-1996), while the last two verified records (United Kingdom 1998 and Greece 1999) were of single birds. Given its mostly passage occurrence, the European status of this globally threatened species is Not Evaluated.
This globally threatened curlew inhabits wet plains in western Siberia, but its exact breeding area remains unknown. As a passage migrant it is known in the Mediterranean regions of Europe, and its main wintering quarters are probably in north-western Africa. During the last decades of last century it has undergone a dramatic population crash, which apparently never stabilised. Its world population counts probably not more than 50-270 individuals, but these figures are based on very few reliable observations. Numenius tenuirostris has only been confirmed breeding near Tara, north of Omsk in Siberia, Russia, between 1914-1924. It migrates west-south-west from its presumed breeding grounds in Siberia through central and eastern Europe, predominantly Russia, Kazakhstan, Ukraine, Bulgaria, Hungary, Romania and Yugoslavia to southern Europe, Greece, Italy, and Turkey, and north Africa, Algeria, Morocco and Tunisia. It has also been reported from Slovenia, Uzbekistan and Turkmenistan. Reports of birds wintering in Iran persist but require confirmation. Regarded as very common in the 19th century, it declined dramatically during the 20th century. Flocks of over 100 birds were recorded from Morocco as late as the 1960s and 1970s. However, between 1980-1990, there were only 103 records involving 316-326 birds, and from 1990-1999, this dropped to 74 records involving 148-152 birds. Most recent records are of 1-3 birds with the exception of a flock of 19 birds in Italy in 1995. In 1994, the population was estimated at only 50-270 birds, but the paucity of recent records suggests it may now be lower than 50 birds.

There is little information available on diet. The birds at Merja Zerga have been recorded taking earthworms and tipulid larvae, while elsewhere other insects (grasshoppers, an earwig and a beetle), molluscs and crustaceans have been recorded as prey. The most detailed observations of foraging behaviour have been made in recent years at Merja Zerga where the species uses two contrasting habitats, brackish grazing marsh and sandy agricultural land on higher ground nearby. In both areas the birds often feed with Eurasian Curlews and the feeding behaviour is broadly similar to that species: the birds walk slowly, occasionally pecking at the surface or probing the soil; if a food item is located, intensive probing results, until the item is extracted. On average 1.5-2.75 food items were obtained per minute, and feeding was concentrated in mid-morning and mid-afternoon, with the birds roosting in the lagoon at other times.

One of the world's most mysterious birds is the slender-billed curlew (Numenius tenuirostris), an elegant wader. It breeds in bogs in the vast Siberian taiga and winters around the Mediterranean Sea. No one knows exactly where the birds breed or spend their winter. The last discovery of a nest dates back to 1924, and it has been several years since the last reliable sighting. Biologists estimate that only 50 birds remain today, and that their population is declining. Some even doubt that any individuals remain. If that were the case, the slender-billed curlew would be the first European bird to go extinct in 150 years. The reason why this is happening is as mysterious as the birds themselves. The most likely cause is hunting in the wintering grounds, but the details remain unknown. This species has an extremely small population and the number of birds recorded annually continues to fall. This is likely to represent a continuing population decline. For these reasons the species qualifies as Critically Endangered. [conservation status from birdlife.org]

Little detailed information can be given on breeding ecology and behaviour, since the only confirmed observations come from just one site at least 70 years ago. This site, near Tara, is close to the northern limit of the forest-steppe zone. The habitat appeared largely unchanged during surveys in 1990 and 1994, and was closer to a taiga marsh than a typical forest-steppe marsh. It is possible that the habitat at this site was not typical of that used by the species, and thus the species may nest further north (in true taiga habitat) or south (in steppe habitat).
In May 1914 a single Slender-billed Curlew nest was found, with four eggs (Eurasian Curlews were also nesting nearby). In 1924 a colony of the species was found, containing 14 nests (within a few meters of each other), at the same site south of Tara. With so few observations there is no way of knowing how common such colonial nesting is. Eggs were found in May. Apparently breeds in small colonies, with nests 2-3 m apart. Nest in dense growth on dry areas within bogs, constructed of dry grass. 4 eggs(?).

Migratory. Few recent observations anywhere due to growing rarity. In 19th century, when numbers larger, part of population migrated south across Turkmenistan and south Caspian to winter in Iran and Iraq, while others passed SW-WSW across Transcaucasia, Ukraine, Balkans (extending into south-east Hungary), and Italy (including Sicily), to winter in North Africa, especially in Maghreb. Stragglers then occurred across Europe, exceptionally north to Baltic and west to Low Countries and Atlantic coast of France. Passage still occurs across Aral-Caspian steppes, Turkmenistan, and Ukraine, and recently reported Iran (38 in 1990, 21 in 1992, 15 in 1993). A few still migrate across Turkey, Balkans, and southern Hungary August-November and March-May, and occasionally occur December-February. Flock of up to 19 birds south-east of Italy January-March 1995. No modern records from Egypt or Libya, but several recent December-February reports from Tunisia. Morocco probably now the main wintering area for the species; recent records mainly November-March.