An unusual Arctic tern has been seen in Siglufjördur in north Iceland in the past days. While Arctic terns are white with a black head, this tern appears to be all black. It is unclear whether this is a black Arctic tern or a black tern that has lost its way. The bird was first seen on July 4.

An Arctic tern. Photo by Páll Stefánsson.

British ornithologists who saw the bird believe that it is a black tern (Lat. Chlidonias niger), called koltherna in Icelandic, which breeds in America but for some reason has drifted across the ocean to Iceland, Morgunbladid reports.

Local Rev. Sigurdur Aegison, who has photographed the bird, said it was difficult to take pictures of it on Wednesday because the Arctic terns (Lat. Sterna paradisaea), kría in Icelandic, were attacking it.

Gudmundur Gudmundsson, a zooecologist at the Icelandic Institute of Natural History, agrees with the British ornithologists, pointing out that the bird has shorter and rounder wings than an Arctic tern and that the tail is much shorter.

However, Yann Kolbeinsson, a physiologist and bird enthusiast, points out that a young Arctic tern does have rounded wings and a short tail. It could be a melanic bird, an Arctic tern which looks like an anti-albino, which is known among birds and other species.

Once in a while, melanin, the chemical which makes the bird dark, completely takes over, Kolbeinsson explained. 

Click here to see a picture of the black (Arctic) tern.