Tuesday, 6 February 2018

Thayer's Gull, Toyd Down, Tidpit, Hampshire - 6th February

After dipping the Thayer's Gull yesterday at Blashford Lakes and learning that the bird had been seen during the day feeding in pig fields at Toyd Down south of Tidpit, Hampshire. I decided that I would drop Tobias at school and spent a couple of hours at the site looking for the bird. When I arrived there were seemingly no gulls to be seen so finding a high point I began scanning, there were many larger gulls heading north up the Avon Valley and then I realised that birds were dropping into the pig fields fields to the east of where I was standing. I parked by the public bridleway and made my way eastwards. Eventually I encountered a large number of gulls feeding and loafing in the pig fields and an adjacent grass field. I set up my scope and began scanning from approximately SU07891694.

Scanning through the flock there were large numbers of gulls, many of which were out of view and I was not hopeful of finding the Thayers. Another birder joined me and after a quick chat we began scanning again, almost immediately I found a pale gull which was hidden in a rut in the ground and of which I could only seen the head and back but I was suspicious. I put the other birder onto this bird and as we watched the bird climbed out of its rut and there it was the Thayer's Gull. We watched the bird for just over an hour as it loafed in the field before it flew a short distance north and out of sight. It was then time to go. Unfortunately, the bird was always fairly distant at around 200m and so my pictures are pretty appalling but I think the main characters can be seen.

There are nine accepted Irish records and none from Great Britain, all from Ireland, although a widely twitched adult from Minsmere on 27th and 28th March 2016 is still under consideration. The following records have been accepted to date:

  • Killybegs, County Donegal - Adult, 16th December 2013
  • Rossaveal, County Galway - 1st winter, 18th February to 5th April  2011.
  • Cleggan, County Galway - 1st winter, 19th January to 10th February 2010.
  • Barnatra, Belmullet, County Mayo - 1st winter, 5th to 19th March 2005.
  • Killybegs, County Donegal - Juvenile, 2nd February to 11th March 2003.
  • Newport Dump, County Mayo - Juvenile, 19th December 1998 to 3rd April 1999.
  • Killybegs, County Donegal - Adult, 22nd February to 10th March 1998.
  • Dargan Road, landfill, County Antrim - Juvenile, 1st to 7th March 1997.
  • The Lough, Cork City Dump - Juvenile, 21st February to 5th March.

The taxonomic history of Thayer's Gull is chequered. The International Ornithological Congress (IOC) checklist (which now forms the basis for the official British list) now consider Thayer's Gull a subspecies of Iceland Gull (see here (page 29) for a detailed discussion). However, HBW Alive recommend maintaining it as a full species pending further studies. The features that identify Thayer's Gull are variable but there is a nice summary article here for 1st winter birds. In summary the key features are:

  • Pale and frosty looking overall appearance to plumage;
  • Concolourous dark brown to black tail;
  • Heavily barred rump;
  • Tertials concolorous with upperparts and being paler than wingtip;
  • Whiteish edges to primaries creating line of white arrowheads on the wingtip; and
  • On open wing dark outer webs to primaries and with dark centres to the secondaries.

An excellent paper on the identification of 2nd year birds can be viewed here.

However, the identification characters can be very complex with intergrades and darker individuals occurring and some are probably not safely identifiable. As always, refer to Olsen and Larsson for a detailed text on gulls, where Thayer's Gull not only features on the cover but is treated as a separate species.