Tern seen in Romania id help request (1 Viewer)

Dear colleagues
I am trying to make sense ( not being an expert) of a Tern that I got a brief sighting of last month in the Danube Delta area of Romania, but was not able to get a photo of. It was apparently fishing in the river.

The bird had a full black cap and thus would have been I guess in summer adult plumage - a clean bird.

As I saw the bird close up I noticed the bill was pure all-black.

Later on when I was thinking about this bird I more or less concluded that it would have been a Gull-billed Tern.

When I thought about this bill I considered other Terns that are seen in the area wouldn't have fit the description, and that therefore it must have been a Gull-billed Tern. A Gull-billed tern would be a lifer for me.

However I have just seen online some photo's of Common Terns with adult plumage and black bills. Perhaps there is some mistake here but I was not aware that summer plumaged Common Terns can have black bills

Please see for example the website here

http://www.tsuru-bird.net/a_species/tern_common/

This website shows a photo of a Common Tern in adult plumage with a black bill. I am now quite confused and no longer certain that the bird I saw was in fact a Gull-billed Tern.

Any advice on this matter would be much appreciated. Thank you.

It's usually only the eastern races of Common Term that have blackish bills, so I would rule out this species. Your bird is also unlikely to have been Gull-billed, which doesn't tend to dive for fish. It also has a distinctive appearance, with a heavy stubby bill and proportionately broad wings. How about Sandwich Tern?

It's pretty unusual to see 'non eastern' common terns with dark bills, but it can happen (often, the legs are darker on these birds too).

It seems likely that your bird was a gull-billed tern. However, I'm not sure it would sit comfortably on my list with that level of certainty!

Maybe of help, IMHO Gull-billed's structure gives more of an impression in flight of say a Med Gull than a Common Tern......also when feeding they tend to hawk and dip over the water (or land) rather than actually dive in.

Dear Andy, Paul, and Simon
Thank you all for your helpful comments.
I just wish now I'd stayed around longer to study it.
It was over the river but I didn't see it actually diving for fish.
The bill was all black and although I have seen Sandwich Terns previously I didn't the impression of that species on this occasion.
The comments about the Eastern Common Tern are helpful too. I guess it most likely was a Gull-billed Tern - to be honest, I can't see what else it might have been. However on this occasion, I think I should keep it as a "maybe".

no, it was not likely a gull-billed tern, kasfig. fishing in the danube is extremely unlikely for gull-billed, even its occurence along the danube branches without fishing is very very unlikely. they are almost always found in the lagoons south of the delta, and within the delta only in the coastal dunes and saline marshes. they usually hunt lizards and large insects over dry habitats. within the delta and along the danube branches you basically get comomon tern and the three species of marsh terns (genus chlidonias). i'd think your bird might have been an adult common tern which cap still was black but bare parts colour (bill) already turned to blackish for the "winter plumage" (or basic plumage). i have photographed an adult common tern with black bill (but not complete black cap, it had a white forehead of course) in september in the danube delta, actually at the coast bordering the delta.

cheers

Thanks, Lou for the additional information which adds to my knowledge store which is ever increasing.
I see now the habitat was wrong. The sighting was too brief. Also, I didn't see that the bill was "stout" as is, of course, the case with this particular species hence its name.