Surinamensis Black Terns

Juv. American Black Tern, South Carolina, August

UK birder Graham Catley, fine photographer and a sharp field birder discovered this typical American Black Tern (surinamensis)on the East coast of the UK..only the fourth record for the UK.

Check out these fine images:

A ‘black tern’ in France, along the Atlantic coast has generated some interest on Bird ID-F:

Showing some characters of the  American subspecies, surinamensis, it is a tricky bird.  Peter Adriaens, from Belgium, commented on the French bird as follows:

Compared to juvenile niger, juvenile surinamensis generally looks darker and more uniform. In my experience, from a distance it may give a rather skua/jaeger-like impression.
There are a few more identification pointers:
* The pattern of the rump and upper tailcoverts usually differs between the two subspecies. In surinamensis, the feathers have only thin, dull grey tips, creating a rather uniformly grey rump that does not contrast with the tail. In the French bird, the rump feathers and upper tailcoverts have wide, pale grey fringes that go all the way up to the base of each feather, making the rump look paler than the tail.
* The outer web of the outermost tail feather is usually dark grey in surinamensis; it seems to be pale grey in the French bird.
* The upper wingcoverts often look rather dull and uniform in surinamensis, because they (almost) lack pale edges. The pattern is more variegated in the French bird, with distinct pale edges and tips to these feathers.
The underwing may fit some surinamensis, but not the typical ones, I would say. There is still quite a bit of white admixed in the central part of the arm. Also, many juvenile surinamensis show a dusky leading edge to the underwing, which is not prominent here. Mind you, I agree that the pattern of the underwing and flanks looks unusual, but it does not seem convincing enough for surinamensis to me.”
Here is a recent, fairly similar Black Tern (niger) from Belgium (all links refer to one and the same bird):
Here are a couple of pages from my notebook and   of my photos of juvenile American Black Terns from South Carolina in late August as reference.

surinamensis Black Terns, Connecticut showing variation of head pattern


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