ML59362841

觀察細節

Two birds in view briefly. Originally identified as Asian House Martin based on shallow tail fork and blackish (?) underwing coverts. Lighting not ideal. The uppertail coverts appear to be white as well as the rump, although the angle of view is not perfect. The two eBird checklists below: https://ebird.org/checklist/S55202410 https://ebird.org/checklist/S52945727 from northern Japan and Alaska, show birds identified as Common House Martins with white rump AND uppertail coverts, blackish underwing coverts, and shallow tail fork. It is not clear which is the more reliable field mark, white uppertail coverts, black underwing coverts, or tail fork. Photo at this link shows lagopodum with dark underwing coverts: https://www.hbw.com/ibc/species/1343897/gallery So perhaps the Tobishima bird in my photos is lagopodum Common (Eastern) House Martin. I would welcome any comments.