Tern in Malaysia: Aleutian or something else? (2 Viewers)

[Dave B]

Photographed today in Penang, Malaysia.

I'd be grateful for any thoughts on the tern arrowed. I did not see the bird in the field. I was taking photos of the roost from a boat, and only found it while checking the photos on the computer. This is the only sharp photo, though I have a couple of out of focus images.

In comparison with the Common Terns on the right, the bill and general proportions look OK for Aleutian Tern, which is a scarce but regular migrant through these parts, with most records in April (it is a lot commoner further south).

However, the overall jizz doesn't strike me as particularly Aleutian-like (hard to say from a single photo I know), and I'm wondering about the transitional head pattern - could an Aleutian could ever look like this?

I'd like to know if there's any other species I should consider, and would value other thoughts.

 

[Dave B]

Bumpety bump! A crop of the head added.

 

[Dave B]

Wow - 156 views and no replies! That must either mean it's really easy or really hard!

 

[lou salomon]

i find it almost a mission impossible, dave. but i haven't seen aleutian yet. i'd expect an aleutian to be slightly darker than your bird, primaries and mantle. apart from bill length i see no clea differences to those (longipennis?) common terns.

 

[Stuart Darbyshire]

no experience of Aleutian, but shouldn't it show some degree of dark lores by now?

 

[rockfowl]

I think its really hard Dave, but I'd agree with Lou on the expectations but again have no experience with Aleutian.

 

[jalid]

Should Aleutian Tern have white area just above eye?

But I mostly came to tell that I do have some experience of the species

 

[Tiraya]

Best bet might be checking images of the species.

https://www.google.com/search?q=ale...K02wWbwIGQAQ&ved=0CAkQ_AUoAQ&biw=1366&bih=667

 

[njlarsen]

We have two in the gallery, one is here: http://www.birdforum.net/gallery/showphoto.php?photo=417616

Niels

 

[Dave B]

i find it almost a mission impossible, dave. but i haven't seen aleutian yet. i'd expect an aleutian to be slightly darker than your bird, primaries and mantle. apart from bill length i see no clea differences to those (longipennis?) common terns.

Thanks Lou and all,

Although the bill is the most obvious difference, I think there are other more subtle differences too, such the overall body bulk, headshape and structure, and lack of dark outer web to the outer tail feathers.

I'm not too worried about the darkness of the grey - longipennis Common is about the same tone as Aleutian, and in strong light they don't always look obviously dark.

But the question I need help with is, if this is not an Aleutian, what else could it be? Are their other alternatives to be considered?

 

[jalid]

I still think that the head pattern, not much white above eye but all-white lores, is easier to explain by Common Tern getting summer plumage than Aleutian Tern. Of other options - I don't believe it to be Arctic Tern, because of long legs (and that would the first record for the country?). Roseate?

 

[Dave B]

I still think that the head pattern, not much white above eye but all-white lores, is easier to explain by Common Tern getting summer plumage than Aleutian Tern. Of other options - I don't believe it to be Arctic Tern, because of long legs (and that would the first record for the country?). Roseate?

Two Common Terns can be seen at the right of the photo. The bill and head structure of these are markedly different from the bird in question. Additionally, it lacks the dark outer web to the outer tail feathers.

I attach a composite showing the head and bill of the mystery tern, an Aleutian and a Roseate. The bill size, though larger than the Aleutian shown, is nearer to Aleutian than to Roseate.

I accept the probability that this tern is not conclusively identifiable, provided it doesn't fit any other species we have not yet considered. Thanks!

 

[ljs]

What about White-Cheeked Tern? The head plumage is rather odd. The black is very well demarcated at the eye level. Plus the dark primaries.. Possibly a non-breeding bird turning into breeding plumage? Anybody familiar with this middle-eastern species? The web seems void of genuine non-breeding white-cheeked terns...

http://2.bp.blogspot.com/-euSiEQRAlDM/UF7afJ4sbWI/AAAAAAAAC9g/FrRdNPc-wGk/s640/IMG_7494+B.JPG

http://farm5.staticflickr.com/4047/4591068631_6bd74da35b_z.jpg

 

[jalid]

See the attached summer-plumaged longipennis from Hong Kong. The structure is not that different to my eye. It seems not to have dark outer webs to outer tail feathers - surely it has, but in a single photo they are not visible for some reason - and it is easy to find more examples of this.

According to Pyle 2008 (IGTNAB 2) Aleutian Tern has culmen length of 31-35, bill depth 6.4-8.1 and Common Tern 32-41, 7.2-10.0 respectively. So there is clear differences but lots of overlap. Of course, measurements do not catch structure completely, but neither does single photo.

 

[Dave B]

See the attached summer-plumaged longipennis from Hong Kong. The structure is not that different to my eye. It seems not to have dark outer webs to outer tail feathers - surely it has, but in a single photo they are not visible for some reason - and it is easy to find more examples of this.

According to Pyle 2008 (IGTNAB 2) Aleutian Tern has culmen length of 31-35, bill depth 6.4-8.1 and Common Tern 32-41, 7.2-10.0 respectively. So there is clear differences but lots of overlap. Of course, measurements do not catch structure completely, but neither does single photo.

Thanks, this is the best alternative explanation to it being Aleutian yet. The bird in the photo you sent is extraordinarily small-billed for a Common Tern. The lightness of the underparts is also odd - so I suspect this may be one of those intergrades with tibetana. Anyway, regalrdless, it does show that my bird could have been a Common and is best left unidentified. Thanks!