Wednesday, May 2, 2012

Photo Quiz 4/25/12 Solution

Well, to start I have to say I am extremely sorry for taking so long to get this up.  To be completely honest, I started to doubt that I knew what this bird was, and I can honestly say, I'm still not 100%.  However, I'll go through the field marks and discuss what the options are, and hopefully come up with an answer.  Shall we take a closer look?
Okay, the photo I gave you is horrible, bad lighting and angle.  But it's pretty clear that it's a tern, which one is far more unclear.  The first thing that I notice in this photo is the primaries.  They appear to have narrow black tips causing a thin black edge to the underwing.  This feature alone would suggest Arctic Tern.  But there's a lot more to think about here.  The bird appears to have a large bill, relatively uniform upperwing, white secondaries, and the from underneath, white primaries and secondaries.  The leading edge of the upperwing appears somewhat darker than the rest of the wing but not black or showing any extreme contrast.

I received a fair number of responses for this, considering how difficult it was, and the most frequent answer I got was Common Tern.  Despite the long bill, I would argue this is not a Common Tern but an Arctic Tern.  Common Tern should show dark secondaries and a dark contrasting (almost black if not black) ulnar bar.  This bird has a fairly uniform upperwing with white secondaries.

Although the lighting is crap and there is a dark shadow over the underwing, I think the important underwing field marks can be made out.  First is, as I pointed out, the narrow black tips to the primaries.  I would expect much broader tips to Common Tern, giving a wedge shaped black band on the primaries.  Though this is not always the case, it is true of most.  The other important character is that all secondaries and primaries are translucent from underneath as opposed to the grayish and contrastingly dark secondaries of Common.  The head also appears small and rounded, but because of the angle I am hesitant to use these characters.

Here is a slightly better photo of a more typical non-breeding Arctic Tern from a better angle.  Note short bill, thin black primary tips, translucent remiges, rounded head, short neck...
And here is another photo of the quiz individual from above.  The better look at the upperwing strongly supports Arctic Tern in my opinion - note overall uniform coloration and white secondaries.  Bill also feels within the norm of a typical Arctic as well.
This is my argument for Arctic Tern.  However, I feel I could benefit from a good discussion on this since my Arctic Tern experience is limited, so if anyone still stands by Common Tern, has anything to add, or just thinks I'm stupid and completely wrong, comment on this post or email me at

¡Winners! - 
Markothy Markus Aurelius "Mark" Dettling
Ryan Ford

Thanks for playing -

~Luke Musher


  1. I would say this bird is too dark and way too short-tailed to be an Arctic tern... Also doesn't look like Common. I am not familiar with terns in your part of the world, do you get black tern? This reminds me of a juvenile black tern, although not a very typical one.

    1. Thanks for your insight, Pedro. This bird appears dark, but I think it's mostly an artifact of the lighting. Also, Arctic Terns lose their long tail streamers after molting into their basic (non-breeding) plumage. For other reasons, too, Black Tern just doesn't fit. For example the underwing is white, and you can see in the last photo that the tail is still pretty long for a Black Tern. I've gotten some feedback from other birds too confirming Arctic.

  2. Benjamin Van Doren from New York also had some insight on this bird. We're both pretty sure that Common Terns in any post juvenal plumage should have a distinct wedge in the outer primaries. This bird doesn't really look anything like a typical Common Tern juvenal, so that's helpful. Also, this bird is likely in between plumages, as some gray body feathers are still present on the underside. This suggests that this bird is an adult. A first year bird might be molting, but it would not have had a gray body as breeding adults have, and thus we wouldn't detect the residual gray on the body.