Slender-billed Curlew

Numenius tenuirostris - Courlis à bec grêle

Systematics

Order
:
Charadriiformes
Family
:
Scolopacidés
Genus
:
Numenius
Species
:
tenuirostris

Descriptor

Vieillot, 1817

Biometrics

Size
: 41 cm
Wingspan
: 80 à 92 cm.
Weight
: 255 à 360 g

Geographic range

Distribution

Identification

The Slender-billed Curlew is a medium-sized curlew, about the same size as the Whimbrel, but slimmer, broader-winged and with a longer, finer, bill. By comparison with the Whimbrel, the 'slender-billed' is rather longer-legged and stands more upright, has a finer, longer neck, and a smaller head. It is clearly paler overall. Upperparts are even paler brown, and the underparts are whitish, with larger and darker, heart-shape or blotches (compared to the buffier underparts with a darker breast and barring of the Whimbrel). Legs are grey-blue (greenish in the Whimbrel).
Three features are diagnostic:
- The head has a dark crown, without a light median stripe, thus contrasting well against the pale side of head (brow, ear-coverts, and cheek) with a dark loral and post-ocular stripe. The dark eye is surrounded by white.
- The bill is about 1.5 times the length of the head. It is broad at the base but tapers gradually throughout its length. Combined with the small pale head, it gives the bird a unique look.
- The flanks are very pale, like the rest of the underparts, and not barred. Instead of barring, there are distinctive heart-shaped or droplet-shaped spots, darker aligned in two directions visible.
The young ones are less typical for this last feature since they show streaking on the flanks.
Beautiful photos of Slender-billed Curlews can be found on the net.

Subspecific information monotypic species

Foreign names

Courlis à bec grêle,
Zarapito fino,
maçarico-de-bico-fino,
Dünnschnabel-Brachvogel,
vékonycsőrű póling,
Dunbekwulp,
Chiurlottello,
smalnäbbad spov,
Smalnebbspove,
hvizdák tenkozobý,
koliha tenkozobá,
Tyndnæbbet Spove,
kaitanokkakuovi,
polit becfí,
Dílaspói,
kulik cienkodzioby,
tievknābja kuitala,
tenkokljuni škurh,
Тонкоклювый кроншнеп,
シロハラチュウシャクシギ,
细嘴杓鹬,
smalnäbbad spov,
細嘴杓鷸,

Voice song and call

play
pause

The Slender-billed Curlew sometimes produces a cour-lii similar to that of the Curlew Sandpiper, although sharper and shorter. A brief and very sharp koui, sometimes repeated twice, is usually given during takeoff or landing, or when the bird is in an alert state. More occasionally, it emits a rapid, rising ti-ti-ti-ti-ti-ti-ti.

Habitat

The breeding habitat consists of large bogs with some shrubs, willows and birches, as well as the transitional stages between bog and forest, large marshes and probably the steppe. The nest is placed on an elevation to be sheltered from water. During migration, it stops at coastal lagoons, salt marshes and adjacent meadows, estuaries, inland fishponds, etc. It winters on coastlines, in bays and lagoons, salt marshes and temporary inland marshes. Birds observed in Morocco seem to be not very demanding in terms of habitat and rather generalists. They can be found on the shore, salty or brackish lagoons, estuaries, temporary or permanent lakes with adjacent marshes, floodplains, meadowy soils and fields.

Behaviour character trait

They are known to be very social outside of the reproductive period, feeding for example alongside Black-tailed Godwits or Curlew Sandpipers. Compared to the latter, they are more mobile on the ground, they run more often, their movements are faster. Their wingbeats are also faster. Slender-billed Curlews are great migrants.

Flight

Typical flight of the Slender-billed Curlew with faster wing beats than the Grey Plover.

Dietfeeding habits

Slender-billed Curlews feed in the same manner as other curlews and godwits. They search for food in the mud by plunging their beak into it. They capture various invertebrates, worms, insect larvae, etc.
Outside of the breeding season, their diet is larger and includes annelids, molluscs, crustaceans, and small insects like grasshoppers, earwigs, and beetles, picked up from the surface or the substrate according to the taxon. They have even been observed catching insects in the bushes. In winter, in Morocco, the birds fed in the morning from sunrise for 2 to 4 hours, then again in the later afternoon until evening. The rest of the time and during the night, they were inactive on the edges of the lagoon.

Reproduction nesting

Little is known about the Slender-billed Curlew. Only one nest has been found near Tara north of Omsk in the early 20th century. Adults seemed to arrive at the breeding grounds mid-May. It is thought they nested in small colonies with nests situated 2 to 3 m to 10 to 15 m apart. The nest was made of dry grasses on grassy hummocks in marshes and bogs and usually four olive-colored eggs with brown markings were laid. The young must have been flight-ready by early July and the birds must have left the breeding grounds in the second half of August.

Geographic range

Breeding grounds of the Slender-billed Curlew have always been poorly known. It is known that they existed in Russia in the wetlands of Central Siberia and it is now thought that some also resided in the Russian steppe north of Central Asia. Its migratory stopover sites and wintering grounds are better known. Typical migratory stopovers include the Evros delta in Greece. Others were found in the Asia Minor and Iran. Typical wintering spots are the wetlands near the coast such as Merdja Zerga in Morocco and interior wetlands like Lake Boughzoul in Algeria or Ischkeul in Tunisia. The Nile Delta and Mesopotamia can also be added.

Threats - protection

IUCN conservation status

Extinct

Threatened

Least
concern

Extinc
in the Wild

Near
threatened

Not
evaluated

EX EW CR EN VU NT LC NE

Slender-billed Curlew populations have greatly declined, while in the 19th century, they were at least equal to those of other wading species, such as Grey and Spotted Curlew. They still migrated in the hundreds to North Africa in the second half of the twentieth century. At present, it is classified as Critically Endangered, and it is even possible that the species is already extinct. The last confirmed sighting dates back to 2001 and since then, the specific research of the species' working group has been fruitless. If this were the case, it would be the first species to disappear from the Western Palearctic for a long time. Personally, I was fortunate enough to see in the late 90s two of the last Moroccan wintering birds at the Merdja Zerga.
Several explanations are advanced for this long decline. Firstly, habitat modifications. We have long been uncertain about its precise breeding grounds. It is now thought that they were in the Russian steppe, an environment that has been completely disrupted for agriculture. Hunting was surely an important negative factor, possibly already on the breeding grounds, but especially on the migration stops and in the wintering areas. The species was apparently a little less wary than its congeners.

Sources of information

IOC World Bird List (v14.2), Gill, F and D Donsker (Eds). 2024-04-18.
Limicoles, gangas et pigeons d'Europe, Paul Géroudet (mise à jour Georges Olioso)
Shorebirds, an identification guide to the waders of the world, Peter Hayman, John Marchant Tony Prater
Birds of the World, The Cornell Lab of Ornithology
xeno-canto, Sharing bird sounds from around the world,

Other sources of interest