Species pairs and groups
Canada/Cackling Goose Branta canadensis/hutchinsii
Western/Semipalmated Sandpiper Calidris mauri/pusilla (winter plumage only)
White-bellied/Black-bellied Storm-petrel Fregetta grallaria/tropica
Band-rumped/Monteiro’s/Cape Verde Storm-petrel Oceanodroma castro/monteiroi/jabejabe
Zino’s/Fea’s/Desertas Petrel Pterodroma madeira/feae/deserta
Fea’s/Desertas Petrel Pterodroma feae/deserta
Audubon’s/Barolo/Boyd’s Shearwater Puffinus lherminieri/baroli/boydi
Ascension/Magnificent/Great Frigatebird Fregata aquila/magnificens/minor
Daurian/Turkestan Shrike Lanius isabellinus/phoenicuroides
Western/Eastern Bonelli’s Warbler Phylloscopus bonelli/orientalis
Sakhalin Leaf/Pale-legged Leaf Warbler Phylloscopus borealoides/tenellipes
Booted/Sykes’s Warbler Iduna caligata/rama
Western/Eastern Orphean Warbler Curruca hortensis/crassirostris
Moltoni’s/Western Subalpine/Eastern Subalpine Warbler Curruca subalpina/iberiae/cantillans
Siberian/Stejneger’s Stonechat Saxicola maurus/stejnegeri
Pied/Western Black-eared/Eastern Black-eared Wheatear Oenanthe pleschanka/hispanica/melanoleuca
Western Black-eared/Eastern Black-eared Wheatear Oenanthe hispanica/melanoleuca
Black-headed/Red-headed Bunting Emberiza melanocephala/bruniceps