"EASTERN" COMMON TERN Sterna hirundo longipennis/tibetana

There are three eastern races of Common Tern, and longipennis is often claimed in the UK. However, the all black bill is not diagnostic, since the other races also have black bills, and the nominate race may also show black in the bill. Indeed, tibetana has a dark red bill-base which is not always apparent. I have not photographed minussensis but since its range overlaps and there are intergrades, it is undoubtedely similar. Although birders sometimes talk of a possible split, overlapping ranges and obvious intergrades render this very unlikely.

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