We spent the afternoon at Eoligarry jetty and managed to re-find the black
tern which I think is an adult in non-breeding plumage. Only the second record
for Barra and the first for 14 years, so at this time of year it's got to be
worth checking to see if it's the American subspecies, especially since we're
on an island that attracts American vagrants in autumn.
The first thing we need to determine is the birds age. I think that this is an
adult due to the dark looking primaries. Juveniles do not show the contrast of
darker looking primaries on paler grey wings. Unfortunately this makes
assigning it to subspecies much harder because a feature of juvenile American
black tern is grey flanks which are easy to see. If we knew for sure that this
was a juvenile then we could say that it's definitely not American black tern
because it has white flanks, but if it's an adult then I'm not sure how to
separate them. I think the rump is meant to be paler on adult American black
tern but I don't think that the quality of the video is good enough to see
that. To be fair I can't even be sure it's an adult at that distance, some images seem to show dark primaries but others don't. Without better views it will just have to go down as black tern. Video slowed
to half speed.
Also from the jetty today, juvenile Sabine's gull, several arctic terns and
white-tailed eagle. It was a windy day but we managed to find a bit of
shelter.
This is probably our favourite birding site on the island, we always seem to
see something good here and if not a bird then otter or bottle-nosed dolphin.
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