Slender-billed Gull Larus genei

(last update: March 02, 2015)

Slender-billed Gull 2CY

Slender-billed Gull is a small to medium gull, only slightly larger than Black-headed Gull. In summer plumage, it lacks a dark hood on the head, but remarkably, as in Black-headed Gull, in winter it develops a dark patch on the ear-coverts (although much smaller). The most noticeable feature in Slender-billed Gull is the long neck, especially when alarmed. Furthermore, the head is elongated with a sloped forehead and the bill is particularly slender.

Slender-billed Gull breed commonly in isolated colonies in the Mediterranean and along the shores of Russian steppe lakes (e.g. Black Sea, Caspian Sea). It winters south along the west coast of Africa, the Mediterranean and to the east: the Arabian peninsular and western India. Most of the description below follows from P.J. Grant: “Gulls, a guide to identification”.

2CY SLENDER-BILLED GULL

Next moult takes place in early spring of the 2nd CY (from February to April into so-called "first summer" plumage) and includes again the body and head. By now, the head turns pale grey without ear-spot. All wing-coverts, remiges and rectrices become strongly worn and the dark bar on the lower lesser coverts bleaches to very pale brown. In a small sample of 2cy birds in Bahrain, quite some birds started to moult outer median and outer lower lesser coverts in this partial moult. In the images of 2cy Slender-billed Gulls in February and March, presented on this web-page, it is obvious that median and lower lesser coverts have been moulted: the dark centred juvenile feathers are replaced for plain grey second generation feathers. As the fringes of some of these feathers are still pretty neat, it is expected these feathers were moulted late in winter. Second generation feathers moulted earlier (September) show extensive wear already. Commonly, the central tail-feathers are included in this partial moult.

From June into October the complete moult starts with the inner primaries. The second generation outer primaries will show more white: the partial black outer-web on the primaries P7-P9 (prominent in first generation primaries) is missing in the second generation flight feathers. Again, P10 has a black outer-web. In general, the second generation primaries resemble those in Black-headed Gull. The breast and belly develop a pink cast, variable in extend and hue. The tail is moulted to all-white feathers, the iris turns white to greenish, the bill turns dark red with the legs slightly paler red. Only a few individuals can be recognised as 2cy (second calendar year) birds in October by the primary coverts, which may still show some dark markings or slightly brownish cast on the centre of a tertial. Otherwise, most 2cy Slender-billed Gulls from October are indistinguishable from adults.