Last Sunday, I was invited to join a small talk called “Gull 102” at Bang Pu, Samut Prakan province. The talk was intended to introduce birders into gulls identification. I gave a talk on gulls in Japan where many species overlap with Thailand. After the talk, we went out to test our identification skills immediately in the field. Bang Pu is no doubt, one of the best places to watch gulls in Thailand. Hundreds of Brown-headed Gulls can be seen around Saphan Sookta bridge where visitors regularly feed them. Odd species can occasionally be found in the mix including rarities and several country’s first records.
Apart from the abundant Brown-headed Gull, we managed to spot several immature and adult Black-headed Gulls and at least 2 first-winter Slender-billed Gulls. The Slender-billed Gull is a rare but regular winter visitor in Thailand and Bang Pu is one of the best places to see it. One of the birds was joining a noisy group of Brown-headed Gulls begging for food just around the start of the bridge.
The evening ended amazingly with a second-year large white-headed gull showing up just before sunset. It was first seen wading through the low tide in the distance then flew in to join the flocks closer to the bridge. Overall, it has very pale appearance making it blend well into the flock of Brown-headed Gulls.
After watching the large gull up close, we were confident that it was a second-year Mongolian Gull, another rarity in Thailand. Since the taxonomy of these large white-headed gulls is still not fully settled, the Mongolian Gull is sometimes considered as a subspecies of either Caspian Gull (Larus cachinnans) or Vega Gull (Larus vegae) or even a full species of its own, Larus mongolicus. It differs from the more regular Heuglin’s Gull (Larus heuglini) by strikingly paler and more whitish appearance. Even in this second-winter plumage, the difference is very apparent. Apart from the overall plumage, mongolicus also has very striking ‘windows’ on the inner primaries unlike heuglini, and even more apparent than in vegae. The black tail band is also narrower, even though it is hard to tell in this case since its tail feathers are moulting. I was really glad to see this bird since it’s an addition to my life list. We stayed and watched and photographed it until there was not enough light before happily said goodbyes and went on home.