It’s great how bird species you see reasonably frequently can sometimes throw you another lesson! I was always under the impression that Mediterranean Gulls were only identifiable in as juvenile/1st winter, 2nd winter/2nd summer and adult winter/adult summer. However when Chris Hind found a Mediterranean Gull in transitional 1st summer <-> 2nd winter plumage; none of us realised that this distinctive individual was going to teach us a bit more.
Chris Hind stuck with this bird as it returned every year subsequently and has managed a really useful set of images and sourced some interesting pieces of information through his own research and discussion with others (notibaly Derek Charles).
Chris has put together the following account of his observations and collective research:
The Workington Mediterranean Gull : Ageing sequence
The regular Mediterranean Gull at Workington has provided an interesting opportunity to observe the succession of plumages through from first summer to its present near-adult state.
I found this bird on 30th July 2009, it lingered around the harbour car park and allowed for photographs both in flight and perched. It was a distinctive individual in having a damaged left leg which was not functional and resulted in the foot projecting visibly from the plumage of the belly both in flight and when perched. The left leg carried a metal ring.
The plumage state at that time was first-summer moulting into second-winter.
The 1st summer features visible were:
- Head showing considerable dark mottling but falling short of a full hood.
- Outer tail feathers with dark sub-terminal band
- Dark secondary band
- Outer four primaries dark
The 2nd winter features becoming visible were:
- White central tail feathers
- White inner primaries
- White tertials
When I photographed the bird next on 23rd September 2009 it was well into 2nd winter plumage. The outer primaries, P8, P9 and P10 were not fully grown. This gave the bird a rather truncated look when perched and a blunt-winged appearance in flight.
By 22nd December the primaries were all fully grown. The distribution of black on the four outer primaries is typical of a bird of this age. This wing pattern is retained through the third summer until the fourth winter.
In its third winter it showed black outer webs to the three outer primaries, P8, P9 and P10. Most Mediterranean Gulls are in full adult plumage by this age and would show a thin black line on the outer web of P10 only. There is a 50% incidence of black on the three outer primaries in females and a 25% incidence of this in males. (Olsen 2004)
By the fourth winter a Mediterranean Gull would certainly be expected to be in full adult plumage. The Workington gull, however, shows a small dark mark on the outer web of each P9 in addition to the normal dark line on P10.
The ringing details of this bird were eventually forthcoming after 18 months of frustratingly fruitless emails !
It was ringed on 27th May 2008 as a nestling (sex unknown) at Kieldrecht, Oost-Vlaanderen, Belgium.
This is a fascinating bird to see and a great example of how much we have to learn!