Slender-billed Gull Larus genei

(last update: March 02, 2015)

Slender-billed Gull 1st cycle (1CY)

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”.

1CY SLENDER-BILLED GULL

Juveniles show a less well-defined brown bar on the median and lower lesser coverts than juvenile Black-headed Gull. Also it lacks the extensive buff-brown wash on the crown and ear-coverts. Juvenile Slender-billed has a predominantly pale head. In Black-headed Gull, the buff extends on the sides of the breast and on the mantle and scapulars, where the feathers become more ginger-toned and show white fringes. This ginger tone is missing in Slender-billed, which has the mantle and scapulars grey-brown. The brown tertials are normally broader fringed grey. The inner greater coverts show an extensive dark brown centre, but from greater covert #5 outwards, the juvenile greater coverts are predominantly grey. The white tail shows a clear black tail-band.

The partial autumn moult (post-juvenile moult into so-called "first winter" plumage) starts right from the moment the nests are abandoned and is completed by September. This partial moult includes the head and under-parts and often median and lower lesser coverts are included. The head, neck and under-parts turn all white except a small dark spot near the eye and ear spot (of variable size). The new mantle and scapulars are moulted to second generation feathers which are all grey. If median and lower lesser coverts are involved, they are replaced by all-grey feathers as well, similar to the juvenile outer greater coverts (although the first replaced feathers may still show a dark wedge in the centre). The tertials are normally excluded and remain juvenile, but some birds include the upper two or three tertials in this partial moult.