Terns, Chachoengsao, Thailand (1 Viewer)

[Milkteeth]

Hello. Could anyone please assist me with some terns? Chachoengsao salt pans, this morning.

Quite distant group on this mud bank. Little Terns, and presumably the slightly larger ones with dark bills are Whiskered. What is the notably larger tern in profile on the left (1st pic)? Next 2 photos are closer crops. Black cap and dark bill. Mottled pale grey chest. Gull-Billed Tern?

And in the final photo, could anyone confirm that the bird in profile on the left is a White-Winged Tern? (Black ‘ear muffs’)

Many thanks!

[I posted this in a Facebook group too, so apologies to anyone who’s seen it twice.]

 

[Butty]

the notably larger tern in profile on the left (1st pic)?

Plausibly common tern. Terns are so tricky...

 

[Milkteeth]

Plausibly common tern. Terns are so tricky...

Thanks for the reply.

Common was my initial thought actually, though I figured Gull-Billed the more likely for the location. Its front/underside was not plain white however, and the bill didn’t look particularly heavy.

 

[lou salomon]

That larger tern is just another Whiskered in alert posture. Bill is too short and general structure wrong for Common Tern. Dark belly moults in later. There is a White-winged Tern in pic 2535 also (prob. two of them).

 

[Milkteeth]

That larger tern is just another Whiskered in alert posture. Bill is too short and general structure wrong for Common Tern. Dark belly moults in later. There is a White-winged Tern in pic 2535 also.

Ah, interesting, thank you.

The bird was definitely larger in the torso regardless of posture, but I guess it’s within the range of variation for the species (Lynx book gives 23-29cm length for Whiskered, some individuals being 25% longer than others). I hadn’t considered such a wide variation in sizes.

Thanks for confirming the W-WT too!

 

[johnallcock]

When you suggest the birds with dark bills are Whiskered, which birds are you referring to? Some of the birds with dark bills on the right of the photo appear to be non-breeding Little Terns - small size, long bill, short legs, long wings and a 'bandana' head pattern.

There are two slightly larger birds with dark bills - the one you mention and another one on the right (in front of the Little Tern with obvious yellow bill). Personally I'm not sure what these are, given the image quality. The bird on the left looks too short-billed for Common in the first photo, but I think this is affect by burn-out on the photo - bill shape and head pattern look better for Common in the picture of this bird preening in my opinion. On the bird on the right, I think the dark bar on the forewing fits Common Tern better. I would say both look a bit too long-winged for Whiskered. But as I said, I'm not really confident about ID for these two birds.

 

[Butty]

Terns are so tricky...

 

[Milkteeth]

When you suggest the birds with dark bills are Whiskered, which birds are you referring to? Some of the birds with dark bills on the right of the photo appear to be non-breeding Little Terns - small size, long bill, short legs, long wings and a 'bandana' head pattern.

There are two slightly larger birds with dark bills - the one you mention and another one on the right (in front of the Little Tern with obvious yellow bill). Personally I'm not sure what these are, given the image quality. The bird on the left looks too short-billed for Common in the first photo, but I think this is affect by burn-out on the photo - bill shape and head pattern look better for Common in the picture of this bird preening in my opinion. On the bird on the right, I think the dark bar on the forewing fits Common Tern better. I would say both look a bit too long-winged for Whiskered. But as I said, I'm not really confident about ID for these two birds.

This is where my confusion came from I think. I took the non-br Little Terns to be Whiskered, as I thought Little retained the yellow bill year round, like a Caspian (these were lifer Littles for me, so I’m pretty clueless on them- my field guide doesn’t have an illustration of them in non-br, and after checking in the Merlin app, there are a lot of breeding plumage pics to swipe through before getting to the black bills.

So, I looked at the trio on the left and thought- Little Tern, the one of similar size must be Whiskered, and so was seeking a larger species to explain the rear bird. When in fact, the photo is two Whiskered terns (as confirmed by @lou salomon ) and the rest Little in various stages of plumage.

I am surprised to discover how big the size differential between Little and Whiskered appears in the field, as the literature gives them just a 2-3cm difference.

Thanks!

 

[gandytron]

image 2566 = Little & Whiskered Terns
image 2569 = Little & Whiskered Terns
image 2567 = Little & Whiskered Terns
image 2535 = two White-winged Terns (middle two birds in the image, not sure about the other left hand bird that is preening, but would guess Whiskered).