One
of the most rewarding things about ornithology in Thailand
is that it is most certainly not a closed book. It is relatively
easy to find something new when birdwatching in Thailand,
be it a previously unknown site rich in birdlife, a range
extension for a particular species or an interesting migratory
date.
However easy these types of discoveries are, few of us expect
to find a new species for the Thai list even though new birds
are added quite regularly. Still, this is what happened quite
recently in a rather convoluted way. In April Alex Vargas
received a message from Geoff Carey informing him that he
had a photograph incorrectly labeled on his pbase gallery.
Instead of it being a Heuglin's Gull, as he and all the other
observers who saw this bird thought, it was in fact a first
winter Slaty-backed Gull Larus schistisagus with
worn plumage. Alex had this verified by other gull experts
and the record has been accepted as a new species for Thailand.
The above photo was taken at Laem
Pak Bia sandspit on the 4th January 2008 where it was
amongst a group of other gulls including Heuglin's and Pallas's
Gulls. The same bird was photographed by other lucky photographers
who gained a new bird for their Thai lists as a result of
their efforts; this reminds us how valuable making proper
records can be, whether it is by photographic records or more
traditional notes and sketches.
The range map given for Slaty-backed Gull in Gulls
of Europe, Asia and North America (Helm Identification Guides)
by Olsen & Larsson (below) suggests that it may not be
that surprising that the species has found its way to Thailand
as its winter range extends southwards towards Thailand from
its breeding grounds and indeed Slaty-backed Gull was a species
that some had identified as one to look out for at gull roosts
in Thailand.
It is also possible, in fact probable, that a number of other
gull species that breed and winter in similar areas to Slaty-backed
and Heuglin's Gulls may also be recorded in Thailand in the
future by vigilant birders. It is particularly surprising,
given how common Vega Gull is in East Asia that this species
has not yet produced any accepted records in Thailand (N.B.
There have been several records strangely not accepted by
the Thai records committee despite there being extremely good
supporting evidence). Rarer species such as Saunder's Gull
and even Glaucous-winged Gull follow similar migration routes
and theoretically could make their way to Thailand and perhaps
the biggest prize of all Asian gulls would be a Relict Gull
- not impossible!
Identifying these gulls can be tricky, but the washed out
appearance of this first winter Slaty-backed Gull is fairly
easy to pick out and adult birds would be very easy to identify
too. However, some ages of this species can be confusing,
making a good guide on this group of birds essential.
Photographing any large gulls that are seen in Thailand is
definitely a worthwhile endeavour as it may be an unidenitifed
rarity that is captured as these further photos of Thailand's
first Slaty-backed Gull prove.
The Gulls
of Europe, Asia & North America by Olsen and Larsson
is an excellent publication that any ornithologist who wants
to get to grips with the many confusing gull species, their
moult pattern and other aspects of their ecology must own.
If it had been available to the observers of this Slaty-backed
Gull when in the field I am sure they would have identified
it at the time.
Central
Mongolia , 20th May-3rd June 2021 - Black-billed
Capercaillie, Oriental Plover, Henderson's Ground Jay, Azure
Tit, Pallas's Sandgrouse: Contact
me for details
Thailand
Raptor Migration, 26th Oct-5th Nov 2021 -
Black Baza, Grey-faced Buzzard, Pied Harrier, Lesser Fish
Eagle, Spoon-billed Sandpiper: Contact
me for details
by Olsen & Larsson (below) suggests that it may not be
that surprising that the species has found its way to Thailand
as its winter range extends southwards towards Thailand from
its breeding grounds and indeed Slaty-backed Gull was a species
that some had identified as one to look out for at gull roosts
in Thailand.
South
Korea, 5-17th January 2021 - Steller's Sea
Eagle, Relict Gull, Red-crowned Crane, White-naped Crane,
Baikal Teal, Solitary Snipe, Asian Rosy Finch: 
Central
Mongolia , 20th May-3rd June 2021 - Black-billed
Capercaillie, Oriental Plover, Henderson's Ground Jay, Azure
Tit, Pallas's Sandgrouse: 
Thailand
Raptor Migration, 26th Oct-5th Nov 2021 -
Black Baza, Grey-faced Buzzard, Pied Harrier, Lesser Fish
Eagle, Spoon-billed Sandpiper: 
