- Cryptoleucopteryx plumbea
- Cryptophaps
- Cryptophaps poecilorrhoa
- Cryptopipo
- Cryptopipo holochlora
- Cryptospiza
- Cryptospiza jacksoni
- Cryptospiza reichenovii
- Cryptospiza salvadorii
- Cryptospiza shelleyi
- Cryptosylvicola
- Cryptosylvicola randrianasoloi
- Crypturellus
- Crypturellus atrocapillus
- Crypturellus bartletti
- Crypturellus berlepschi
- Crypturellus boucardi
- Crypturellus brevirostris
- Crypturellus casiquiare
- Crypturellus cinereus
- Crypturellus cinnamomeus
- Crypturellus duidae
- Crypturellus erythropus
- Crypturellus kerriae
- Crypturellus noctivagus
- Crypturellus obsoletus
- Crypturellus parvirostris
- Crypturellus ptaritepui
- Crypturellus soui
- Crypturellus strigulosus
- Crypturellus tataupa
- Crypturellus transfasciatus
- Crypturellus undulatus
- Crypturellus variegatus
- Cuba
- Cuban Amazon
- Cuban Black-Hawk
- Cuban Black Hawk
- Cuban Blackbird
- Cuban Bullfinch
- Cuban Crow
- Cuban Emerald
- Cuban Flicker
- Cuban Gnatcatcher
- Cuban Grassquit
- Cuban Green Woodpecker
- Cuban Kite
- Cuban Lizard-Cuckoo
- Cuban Lizard Cuckoo
- Cuban Macaw
- Cuban Martin
- Cuban Nightjar
- Cuban Oriole
- Cuban Palm Crow
- Cuban Parakeet
- Cuban Parrot
- Cuban Pewee
- Cuban Pygmy-Owl
- Cuban Pygmy Owl
- Cuban Screech-Owl
- Cuban Screech Owl
- Cuban Solitaire
- Cuban Tody
- Cuban Trogon
- Cuban Vireo
- Cuban Whistling-Duck
- Cuban Whistling Duck
- Cuckmere Haven
- Cuckoo-Hawk
- Cuckoo-Hawks
- Cuckoo-Roller
- Cuckoo-finch
- Cuckoo Duck
- Cuckoo Finch
- Cuckoo Hawk
- Cuckoo Hawks
- Cuckoo Roller
- Cuckoo Weaver
- Cuculidae
- Cuculiformes
- Cuculus
- Cuculus canorus
- Cuculus clamosus
- Cuculus crassirostris
- Cuculus flabelliformis
- Cuculus fugax
- Cuculus gularis
- Cuculus horsfieldi
- Cuculus hyperythrus
- Cuculus lepidus
- Cuculus micropterus
- Cuculus nisicolor
- Cuculus optatus
- Cuculus pallidus
- Cuculus pectoralis
- Cuculus poliocephalus
- Cuculus rochii
- Cuculus saturatus
- Cuculus solitarius
- Cuculus sparverioides
- Cuculus vagans
- Cuculus varius
- Cudgimaruk
- Cueva de los Portales
- Culbin Sands
- Culbin Sands RSPB Reserve Scotland
- Culicicapa
- Culicicapa ceylonensis
- Culicicapa helianthea
- Culicicapa helianthea zimmeri
- Culicivora
- Culicivora caudacuta
- Cumbria
- Cundinamarca Antpitta
- Cupwing
- Cupwings
- Curacao
- Curaeus
- Curaeus curaeus
- Curaeus forbesi
- Curassow
- Curassows
- Curaçao
- Curl-breasted Manucode
- Curl-crested Aracari
- Curl-crested Jay
- Curl-crested Manucode
- Curlew Sandpiper
- Curruca balearica
- Curruca boehmi
- Curruca buryi
- Curruca cantillans
- Curruca communis
- Curruca conspicillata
- Curruca crassirostris
- Curruca curruca
- Curruca deserti
- Curruca deserticola
- Curruca hortensis
- Curruca inornata
- Curruca layardi
- Curruca leucomelaena
- Curruca lugens
- Curruca melanocephala
- Curruca melanothorax
- Curruca mystacea
- Curruca nana
- Curruca nisoria
- Curruca ruppeli
- Curruca sarda
- Curruca subalpina
- Curruca subcoerulea
- Curruca undata
- Cursorius
- Cursorius Coromandelicus
- Cursorius africanus
- Cursorius coromandelicus
- Cursorius cursor
- Cursorius rufus
- Cursorius somalensis
- Cursorius temminckii
- Curve-billed Reedhaunter
- Curve-billed Scythebill
- Curve-billed Thrasher
- Curve-billed Tinamou
- Curve-winged Saberwing
- Curve-winged Sabrewing
- Cusco Brush-Finch
- Cusco Brush Finch
- Cusco Brushfinch
- Cut-throat
- Cut-throat Finch
- Cut-throat Weaver
- Cutia
- Cutia legalleni
- Cutia nipalensis
- Cutthroat Finch
- Cuvier's Brush Turkey
- Cuvier's Rail
- Cuvier's Toucan
- Cuvier's brush-turkey
- Cuzco Brush-Finch
- Cuzco Brush Finch
- Cuzco Brushfinch
- Cuzco Tapaculo
- Cuzco Warbler
- Cwm Clydach
- Cwm Clydach RSPB Reserve Wales
- Cyanerpes
- Cyanerpes caeruleus
- Cyanerpes caeruleus longirostris
- Cyanerpes cyaneus
- Cyanerpes cyaneus carneipes
- Cyanerpes cyaneus eximius
- Cyanerpes cyaneus holti
- Cyanerpes lucidus
- Cyanerpes lucidus isthmicus
- Cyanerpes nitidus
- Cyanicterus
- Cyanicterus cyanicterus
- Cyanistes
- Cyanistes Caeruleus
- Cyanistes caeruleus
- Cyanistes caeruleus raddei
- Cyanistes cyanus
- Cyanistes flavipectus
- Cyanistes semilarvatus
- Cyanistes teneriffae
- Cyanistes teneriffae teneriffae
- Cyanistes teneriffae ultramarinus
- Cyanistes varius
- Cyanochen
- Cyanochen cyanoptera
- Cyanochen cyanopterus
- Cyanocitta
- Cyanocitta cristata
- Cyanocitta stelleri
- Cyanocompsa
- Cyanocompsa brissonii
- Cyanocompsa cyanea
- Cyanocompsa cyanoides
- Cyanocompsa parellina
- Cyanocompsa rothschildii
- Cyanocorax
- Cyanocorax Chrysops
- Cyanocorax affinis
- Cyanocorax beecheii
- Cyanocorax caeruleus
- Cyanocorax cayanus
- Cyanocorax chrysops
- Cyanocorax cristatellus
- Cyanocorax cyanomelas
- Cyanocorax cyanopogon
- Cyanocorax dickeyi
- Cyanocorax hafferi
- Cyanocorax heilprini
- Cyanocorax luxuosus
- Cyanocorax melanocyaneus
- Cyanocorax morio
- Cyanocorax mystacalis
- Cyanocorax sanblasianus
- Cyanocorax violaceus
- Cyanocorax yncas
- Cyanocorax yucatanicus
- Cyanocorax yucatanicus yucatanicus
- Cyanoderma
- Cyanoderma ambiguum
- Cyanoderma chrysaeum
- Cyanoderma erythropterum
- Cyanoderma melanothorax
- Cyanoderma pyrrhops
- Cyanoderma ruficeps
- Cyanoderma rufifrons
- Cyanograucalus
- Cyanograucalus azureus
- Cyanolanius
- Cyanolanius comorensis
- Cyanolanius madagascarinus
- Cyanolimnas
- Cyanolimnas cerverai
- Cyanoliseus
- Cyanoliseus bloxami
- Cyanoliseus patagonus
- Cyanoliseus patagonus andinus
- Cyanoliseus patagonus bloxami
- Cyanoloxia
- Cyanoloxia brissonii
- Cyanoloxia cyanoides
- Cyanoloxia glaucocaerulea
- Cyanolyca
- Cyanolyca argentigula
- Cyanolyca armillata
- Cyanolyca cucullata
- Cyanolyca mirabilis
- Cyanolyca nana
- Cyanolyca nanus
- Cyanolyca pulchra
- Cyanolyca pumilo
- Cyanolyca turcosa
- Cyanolyca viridicyanus
- Cyanomitra
- Cyanomitra Cyanolaema
- Cyanomitra alinae
- Cyanomitra bannermani
- Cyanomitra cyanolaema
- Cyanomitra obscura
- Cyanomitra olivacea
- Cyanomitra oritis
- Cyanomitra veroxii
- Cyanomitra verticalis
- Cyanophaia
- Cyanophaia bicolor
- Cyanopica
- Cyanopica cooki
- Cyanopica cyana
- Cyanopica cyanus
- Cyanopsitta
- Cyanopsitta spixii
- Cyanoptila
- Cyanoptila cumatilis
- Cyanoptila cyanomelana
- Cyanoptila cyanomelana cyornis
- Cyanoramphus
- Cyanoramphus auriceps
- Cyanoramphus cookii
- Cyanoramphus forbesi
- Cyanoramphus hochstetteri
- Cyanoramphus malherbi
- Cyanoramphus novaezelandiae
- Cyanoramphus novaezelandiae novaezelandiae
- Cyanoramphus saisseti
- Cyanoramphus saissetti
- Cyanoramphus ulietanus
- Cyanoramphus unicolor
- Cyanoramphus zealandicus
- Cyclarhis
- Cyclarhis gujanensis
- Cyclarhis gujanensis parva
- Cyclarhis nigrirostris
- Cyclopsitta
- Cyclopsitta diophthalma
- Cyclopsitta diophthalma macleayana
- Cyclopsitta gulielmitertii
- Cyclorrhynchus psittacula
- Cygnus
- Cygnus atratus
- Cygnus bewickii
- Cygnus buccinator
- Cygnus columbianus
- Cygnus columbianus bewickii
- Cygnus cygnus
- Cygnus melancoryphus
- Cygnus melanocoryphus
- Cygnus olor
- Cymbilaimus
- Cymbilaimus lineatus
- Cymbilaimus sanctaemariae
- Cymbirhynchus
- Cymbirhynchus macrorhynchos
- Cynanthus
- Cynanthus doubledayi
- Cynanthus latirostris
- Cynanthus latirostris magicus
- Cynanthus sordidus
- Cyornis


