ABA Difficulties (5 is most Difficult)
[Sorted by Code and Taxonomic Order]


5 Wandering Albatross
5 Shy Albatross
5 Black-browed Albatross
5 Herald Petrel
5 Stejneger's Petrel
5 White-chinned Petrel
5 Streaked Shearwater
5 Wedge-tailed Shearwater
5 Little Shearwater
5 European Storm-Petrel
5 Wedge-rumped Storm-Petrel
5 Red-tailed Tropicbird
5 Great Frigatebird
5 Lesser Frigatebird
5 Yellow Bittern
5 Chinese Egret
5 Little Egret
5 Western Reef-Heron
5 Scarlet Ibis
5 Jabiru
5 Pink-footed Goose
5 Lesser White-fronted Goose
5 Falcated Duck
5 Spot-billed Duck
5 Baikal Teal
6 Labrador Duck
5 Steller's Sea-Eagle
5 Crane Hawk
5 Roadside Hawk
5 Collared Forest-Falcon
5 Eurasian Kestrel
5 Aplomado Falcon
5 Eurasian Hobby
2 Plain Chachalaca
5 Himalayan Snowcock
5 Corn Crake
5 Paint-billed Crake
5 Spotted Rail
5 Azure Gallinule
5 Eurasian Coot
5 Common Crane
5 Double-striped Thick-knee
5 Northern Lapwing
5 European Golden-Plover
5 Collared Plover
5 Little Ringed Plover
5 Eurasian Oystercatcher
5 Black-winged Stilt
5 Oriental Pratincole
5 Marsh Sandpiper
5 Green Sandpiper
5 Little Curlew
5 Eskimo Curlew
5 Slender-billed Curlew
5 Far Eastern Curlew
5 Eurasian Curlew
5 Great Knot
5 Spoonbill Sandpiper
5 Broad-billed Sandpiper
5 Jack Snipe
5 Pin-tailed Snipe
5 Eurasian Woodcock
5 Band-tailed Gull
5 Yellow-legged Gull
5 Large-billed Tern
5 White-winged Tern
6 Great Auk
5 Scaly-naped Pigeon
5 European Turtle-Dove
5 Oriental Turtle-Dove
5 Zenaida Dove
6 Passenger Pigeon
5 Key West Quail-Dove
5 Ruddy Quail-Dove
5 Thick-billed Parrot
5 Common Cuckoo
5 Oriental Cuckoo
5 Oriental Scops-Owl
5 Mottled Owl
5 Jungle Nightjar
5 White-collared Swift
5 White-throated Needletail
5 Common Swift
5 Fork-tailed Swift
5 Antillean Palm Swift
5 Green-breasted Mango
5 Xantus's Hummingbird
5 Cinnamon Hummingbird
5 Bahama Woodstar
5 Bumblebee Hummingbird
5 Eared Trogon
5 Hoopoe
5 Eurasian Wryneck
5 Great Spotted Woodpecker
6 Ivory-billed Woodpecker
5 Greenish Elaenia
5 Caribbean Elaenia
5 Tufted Flycatcher
5 La Sagra's Flycatcher
5 Variegated Flycatcher
5 Nutting's Flycatcher
5 Loggerhead Kingbird
5 Masked Tityra
5 Brown Shrike
5 Thick-billed Vireo
5 Yucatan Vireo
5 Cuban Martin
5 Gray-breasted Martin
5 Southern Martin
5 Brown-chested Martin
5 Common House-Martin
5 Middendorff's Grasshopper-Warbler
5 Lanceolated Warbler
5 Wood Warbler
5 Dusky Warbler
5 Narcissus Flycatcher
5 Mugimaki Flycatcher
5 Red-breasted Flycatcher
5 Siberian Flycatcher
5 Gray-spotted Flycatcher
5 Asian Brown Flycatcher
5 Siberian Blue Robin
5 Red-flanked Bluetail
5 Stonechat
5 Fieldfare
5 Redwing
5 White-throated Robin
5 Aztec Thrush
5 Bahama Mockingbird
5 Blue Mockingbird
5 Siberian Accentor
5 Citrine Wagtail
5 Gray Wagtail
5 Tree Pipit
5 Pechora Pipit
5 Gray Silky-flycatcher
6 Bachman's Warbler
5 Crescent-chested Warbler
5 Gray-crowned Yellowthroat
5 Slate-throated Redstart
5 Fan-tailed Warbler
5 Golden-crowned Warbler
5 Flame-colored Tanager
5 Yellow-faced Grassquit
5 Black-faced Grassquit
5 Worthen's Sparrow
5 Pine Bunting
5 Little Bunting
5 Yellow-breasted Bunting
5 Gray Bunting
5 Pallas's Bunting
5 Reed Bunting
5 Yellow Grosbeak
5 Tawny-shouldered Blackbird
5 Black-vented Oriole
5 Streak-backed Oriole
5 Common Chaffinch
5 Common Rosefinch
5 Eurasian Siskin
5 Oriental Greenfinch
5 Eurasian Bullfinch
 
4 Arctic Loon
4 Laysan Albatross
4 Short-tailed Albatross
4 Yellow-nosed Albatross
4 Mottled Petrel
4 Murphy's Petrel
4 Cook's Petrel
4 White-faced Storm-Petrel 
4 Band-rumped Storm-Petrel
4 Least Storm-Petrel
4 White-tailed Tropicbird
4 Red-billed Tropicbird
4 Blue-footed Booby
4 Red-footed Booby
4 Greater Flamingo
4 Bean Goose
4 Barnacle Goose
4 Whooper Swan
4 Muscovy Duck
4 White-cheeked Pintail
4 Garganey
4 Common Pochard
4 Smew
4 Masked Duck
4 White-tailed Eagle
4 Mongolian Plover
4 Common Ringed Plover
4 Eurasian Dotterel
4 Northern Jacana
4 Common Greenshank
4 Spotted Redshank
4 Wood Sandpiper
4 Gray-tailed Tattler
4 Common Sandpiper
4 Terek Sandpiper
4 Bristle-thighed Curlew
4 Black-tailed Godwit
4 Red-necked Stint
4 Little Stint
4 Temminck's Stint
4 Long-toed Stint
4 Curlew Sandpiper
4 Slaty-backed Gull
4 Black Noddy
4 Craveri's Murrelet
4 Whiskered Auklet
4 Ruddy Ground-Dove
4 Buff-collared Nightjar
4 Green Violet-ear
4 White-eared Hummingbird
4 Berylline Hummingbird
4 Plain-capped Starthroat
4 Siberian Rubythroat
4 Bluethroat
4 Eyebrowed Thrush
4 Dusky Thrush
4 Clay-colored Robin
4 Rufous-backed Robin
4 Black-backed Wagtail
4 Fork-tailed Flycatcher
4 Eurasian Jackdaw
4 Bahama Swallow
4 Siberian Tit
4 Black-capped Gnatcatcher
4 Olive-backed Pipit
4 Rufous-capped Warbler
4 Bananaquit
4 Stripe-headed Tanager
4 White-collared Seedeater
4 Rustic Bunting
4 Blue Bunting
4 Shiny Cowbird
4 Brambling
4 Hawfinch
 
3 Black-footed Albatross
3 Black-capped Petrel
3 Flesh-footed Shearwater
3 Buller's Shearwater
3 Masked Booby
3 Brown Booby
3 Tufted Duck
3 Spectacled Eider
3 Hook-billed Kite
3 Gyrfalcon
3 Yellow Rail
3 Black Rail
3 Bar-tailed Godwit
3 Sharp-tailed Sandpiper
3 Ruff
3 Great Skua
3 South Polar Skua
3 Little Gull
3 Lesser Black-backed Gull
3 Yellow-footed Gull
3 Ross's Gull
3 Ivory Gull
3 Bridled Tern
3 Brown Noddy
3 Red-billed Pigeon
3 Mangrove Cuckoo
3 Ferruginous Pygmy-Owl
3 Great Gray Owl
3 Boreal Owl
3 Antillean Nighthawk
3 Violet-crowned Hummingbird
3 Elegant Trogon
3 Yellow-green Vireo
3 Tamaulipas Crow
3 Sky Lark
3 Northern Wheatear
3 Yellow Wagtail
3 White Wagtail
3 Red-throated Pipit
3 Colima Warbler
3 Tropical Parula
3 Kirtland's Warbler
3 Connecticut Warbler
3 Five-striped Sparrow
3 McKay's Bunting
 
2 Yellow-billed Loon
2 Least Grebe
2 Northern Fulmar
2 Cory's Shearwater
2 Pink-footed Shearwater
2 Greater Shearwater
2 Short-tailed Shearwater
2 Manx Shearwater
2 Black-vented Shearwater
2 Audubon's Shearwater
2 Wilson's Storm-Petrel
2 Fork-tailed Storm-Petrel
2 Leach's Storm-Petrel
2 Ashy Storm-Petrel
2 Black Storm-Petrel
2 Red-faced Cormorant
2 Emperor Goose
2 Steller's Eider
2 Snail Kite
2 Common Black-Hawk
2 Short-tailed Hawk
2 White-tailed Hawk
2 Zone-tailed Hawk
2 Crested Caracara
2 Merlin
2 Peregrine Falcon
2 Sage Grouse
2 Spruce Grouse
2 White-tailed Ptarmigan
2 Greater Prairie-chicken
2 Lesser Prairie-chicken
2 Sharp-tailed Grouse
2 Montezuma Quail
2 Mountain Quail
2 Clapper Rail
2 King Rail
2 Limpkin
2 Whooping Crane
2 Mountain Plover
2 Red Phalarope
2 Pomarine Jaeger
2 Parasitic Jaeger
2 Long-tailed Jaeger
2 Thayer's Gull
2 Iceland Gull
2 Red-legged Kittiwake
2 Sabine's Gull
2 Elegant Tern
2 Roseate Tern
2 Aleutian Tern
2 Sooty Tern
2 Dovekie
2 Thick-billed Murre
2 Razorbill
2 Black Guillemot
2 Kittlitz's Murrelet
2 Xantus's Murrelet
2 Ancient Murrelet
2 Cassin's Auklet
2 Parakeet Auklet
2 Least Auklet
2 Crested Auklet
2 Atlantic Puffin
2 Horned Puffin
2 White-tipped Dove
2 Budgerigar
2 Canary-winged Parakeet
2 Red-crowned Parrot
2 Smooth-billed Ani
2 Groove-billed Ani
2 Barn Owl
2 Flammulated Owl
2 Eastern Screech-Owl
2 Western Screech-Owl
2 Whiskered Screech-Owl
2 Snowy Owl
2 Northern Hawk Owl
2 Northern Pygmy-Owl
2 Elf Owl
2 Spotted Owl
2 Long-eared Owl
2 Short-eared Owl
2 Northern Saw-whet Owl
2 Pauraque
2 Common Poorwill
2 Chuck-will's-widow
2 Whip-poor-will
2 Black Swift
2 Broad-billed Hummingbird
2 Buff-bellied Hummingbird
2 Blue-throated Hummingbird
2 Magnificent Hummingbird
2 Lucifer Hummingbird
2 Ringed Kingfisher
2 Green Kingfisher
2 Red-cockaded Woodpecker
2 Three-toed Woodpecker
2 Northern Beardless-Tyrannulet
2 Greater Pewee
2 Buff-breasted Flycatcher
2 Dusky-capped Flycatcher
2 Great Kiskadee
2 Sulphur-bellied Flycatcher
2 Tropical Kingbird
2 Couch's Kingbird
2 Thick-billed Kingbird
2 Gray Kingbird
2 Rose-throated Becard
2 Black-capped Vireo
2 Black-whiskered Vireo
2 Green Jay
2 Brown Jay
2 Mexican Jay
2 Pinyon Jay
2 Crested Myna
2 Bendire's Thrasher
2 Le Conte's Thrasher
2 Sprague's Pipit
2 Mexican Chickadee
2 Red-whiskered Bulbul
2 Arctic Warbler
2 Golden-cheeked Warbler
2 Swainson's Warbler
2 Red-faced Warbler
2 Hepatic Tanager
2 Olive Sparrow
2 Bachman's Sparrow
2 Botteri's Sparrow
2 Rufous-winged Sparrow
2 Black-chinned Sparrow
2 Baird's Sparrow
2 Henslow's Sparrow
2 Le Conte's Sparrow
2 Smith's Longspur
2 Varied Bunting
2 Spot-breasted Oriole
2 Altamira Oriole
2 Audubon's Oriole
2 Hoary Redpoll
2 Eurasian Tree Sparrow