michahellis (Mediterranean Yellow-legged Gull) in south west France -- First Impresions

The birds here were among 250 present in the Royan/Isle d'Oléron area on the Atlantic coast of south-west France in August 1991.

They meet the criteria for Mediterranean Yellow-legged Gull of Garner & Quinn (1997). It is generally accepted that this population recently moved north from the Mediterranean to colonise the area (Yésou, 1991). The birds here may of course have come from populations further south. In any event they are not considered to be Atlantic Yellow-legged Gulls.

Differences between Mediterranean and Southern Atlantic Yellow-legged Gulls are given in the Southern Atlantic account.

The photographs show the large size and heavy build of the Mediterranean form with the angular (sometimes squarish) head shape, long legs and often a cold steel-grey mantle colour in the adults. The chests are very bold and protruding and the bills heavy and stubby. The shade of the mantle is thought to be slightly paler than that of the Southern Atlantic form but darker than that of argenteus seen in the same visit on the Atlantic coast of France.

The first-summers show pale heads with dark eye spot, all black bills, grey on scapulars and back, very mottled coverts, broad white tips to tertials and a reddish tinge, all features commonly found in Mediterranean Yellow-legged Gull of this age.

Further interesting features of this form noted were:

• Their long calls which are deep and guttural resembling Great Black-backed Gull marinus to some extent, as also reported by Vinnicombe, Cramp and Dwight. These calls are unlike the shrill graellsii found throughout much of the Southern Atlantic range.

• Their slightly later moult: in mid-August (11th) the moult of adults was slightly behind that in the western Canaries with typically P6 growing and P7 missing.

• Their tendency for much faded bare parts in moult with some adults showing indistinct red gonydeal spots and pale yellow bills and legs. Third-summers can show legs with a pink tinge. The heads of adults appear white in bright sunshine but third-summers may show quite heavy speckling over the entire head and in less intense light some adults can show a fine speckling over the crown, around the eyes and on the nape.

Features not assessed personally were:

• The proportion of adults with a mirror on P9 -- thought to be 50% from other studies and hence more frequent than the 23% on the Southern Atlantic form.

• The structure of the wing tip on the folded wing -- thought by others to generally involve equal spacing of the primary tips P7-P10 rather than the bunching of the tips of P8-P10 as found in the Southern Atlantic form. (best assessed post-moult)

© Copyright Nick Rossiter 2000.

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