Tern ID

[Myer Bornstein]

I know the tern on the right is a common tern what is the one on the left. Taken at South Beach Chatham Mass Nikon D7k Sigma 300 f 2.8 +1.4 TX ISO 400 1/1600 f8
Minimal adjustment LR In PS moved left tern closer to teh right tern for better viewing
Thanks

[John Chardine]

Hi Myer- Forster's Terns, which are very similar to Common Terns in adult plumage, have this "bandit" patch around their eye and the back of their head when they are young.

[Myer Bornstein]

John
Thanks for he ID :)

[Dave Irons]

Myer,

As John Chardine points out, this is indeed a Forster's Tern, however it is not the same age as the Common Tern. If you look closely, the Common Tern has some brownish scalloping on the mantle (center of the back), which indicates that it is a juvenile (hatched this summer). A Forster's Tern of the same age would show similar brown scalloping (even more so than a Common). Unlike other small Sterna terns, the black mask surrounding the eye of a Forster's does not wrap across the nape connecting with the patch on the other side of the head. This is not discussed in most field guides, but Forster's Terns actually don't attain a definitive adult breeding plumage until their fourth year. Also, in between their hatch year and their first summer (a calendar year after hatching) they molt from first basic (winter plumage) directly to second basic plumage with no alternate (breeding or summer) plumage in between. Without getting a better look at the mantle, tertials, and wingtips of your bird, I would be hesitant to age it, other than to say that it seems to be older than hatch-year based on the apparent clean white nape. Once past the first basic plumage (attained in the fall after hatching), basic/winter plumage Forster's Terns will look like this bird each and every winter.

A couple years ago, I published this piece on the molt sequence and summer plumages of Forster's Terns: http://www.birdfellow.com/journal/2009/08/19/photo_essay_forster_s_tern_plumage_sequence

In addition to being a bit larger, and distinctly heavier-billed, Forster's Terns never show the dark carpal bar on wing, a mark that is always shown by basic plumaged Common Terns. This is a really nice comparison photo. Do you have any profile shots of this bird that might give us a better view of the lower wings and tertials?

Dave Irons

[John Chardine]

Thanks Dave. Makes sense. And I have seen adult Forster's in Basic plumage with the eye patch so my post was misleading.

[Arthur Morris]

Great stuff Dave. Super to have you here.