Sunday, 17 February 2008

'Late' juvenile Common Gull

A curiously plumaged Common Gull continues to raise eyebrows on its intermittent appearances in Alexandra Park. First seen more than a week ago, it was present on the reservoir again yesterday afternoon (Saturday 16 February), and this morning was on ice on the boating pond late morning.

This immature bird is in the 'wrong' plumage for February, having not yet moulted out of the juvenile plumage it has had since last summer. Almost all other local first-winter Common Gulls are now showing the classic even, mid-grey 'saddle' on the upperparts, contrasting brownish wing coverts and whiter underparts, but this distinctive individual retains its greyish-brown, pale-fringed scapulars and brown-streaked head and breast indicative of juvenile plumage.

It is perhaps a late-hatched bird from last year from the north of the breeding range which is not yet ready to moult, though by mid-February this plumage is surely unusual. Interestingly, it also appears fairly large and long-billed, perhaps raising the possibility that it may have originated from further east, towards the range of the subspecies heinei. This larger Russian race is said to be essentially inseparable in the field from nominate canus, although first-years sometimes have heavier head and underpart markings "forming complete dark-spotted necklace", rather like the Alexandra Park bird (see Gulls of Europe, Asia and North America by Klaus Malling Olsen, Helm, 2003).

Common Gull is a regular visitor in good numbers to the reservoir and boating pond in winter, and the second most numerous gull after Black-headed Gull (for example, 429 of the latter and 78 of the former were counted on the reservoir on Saturday afternoon, 16 February).

Photos: Dominic Mitchell