| All names | Aden gwyr | Bombycilla garrulus |
| All names | Aderyn adein goch | Turdus iliacus |
| All names | Aderyn bronfraith | Turdus philomelos |
| All names | Aderyn corph | Strix aluco |
| All names | Aderyn cywarch | Carduelis cannabina |
| All names | Aderyn du | Turdus merula |
| All names | Aderyn du'r dwr | Cinclus cinclus |
| All names | Aderyn eira | Plectrophenax nivalis |
| All names | Aderyn y bwn | Botaurus stellaris |
| All names | Aderyn y to | Passer domesticus |
| All names | Aderyn y tô | Passer domesticus |
| All names | Aderyn-bwn America | Botaurus lentiginosus |
| All names | Aderyn-bwn lleiaf | Ixobrychus minutus |
| All names | Aderyn-drycin bach | Puffinus assimilis |
| All names | Aderyn-drycin Cory | Calonectris diomedea |
| All names | Aderyn-drycin du | Puffinus griseus |
| All names | Aderyn-drycin Manaw | Puffinus puffinus |
| All names | Aderyn-drycin mawr | Puffinus gravis |
| All names | Aderyn-Drycin Mediterranean | Puffinus yelkouan |
| All names | Aderyn-drycin Môr y Canoldir | Puffinus yelkouan |
| All names | Aderyn-drycin y Baleares | Puffinus mauretanicus |
| All names | Aderyn-drycin y graig | Fulmarus glacialis |
| All names | Aderyn-y-cyrph | Strix aluco |
| All names | Aderyn-y-cyrs | Acrocephalus scirpaceus |
| All names | Aderyn-yr-eira | Caprimulgus europaeus |
| All names | Alarch Bewick | Cygnus columbianus |
| All names | Alarch dof | Cygnus olor |
| All names | Alarch dôf | Cygnus olor |
| All names | Alarch gwyllt | Cygnus cygnus |
| All names | Alarch y gogledd | Cygnus cygnus |
| All names | Albatros aelddu | Thalassarche melanophris |
| All names | Albatros aelldu | Thalassarche melanophris |
| All names | Alorch Bewick | Cygnus columbianus |
| All names | Alorch dof | Cygnus olor |
| All names | Alorch y gogledd | Cygnus cygnus |
| All names | Asgell-arian | Fringilla coelebs |
| All names | Asgell-hir | Apus apus |
| All names | Barcud | Milvus milvus |
| All names | Barcud coch | Milvus milvus |
| All names | Barcud ddu | Milvus migrans |
| All names | Barcud glâs | Circus cyaneus |
| All names | Barcut du | Milvus migrans |
| All names | Barcutan | Milvus milvus |
| All names | Barfog (Y) | Panurus biarmicus |
| All names | Benfelen (Y) | Emberiza citrinella |
| All names | Bengoch | Carduelis flammea |
| All names | Benloyn-fwyaf (Y) | Parus major |
| All names | Benloyn-gynffonhir (Y) | Aegithalos caudatus |
| All names | Benloyn-lygliw (Y) | Periparus ater |
| All names | Bod | Milvus milvus |
| All names | Bod bacsiog | Buteo lagopus |
| All names | Bod glas | Falco columbarius |
| All names | Bod Montagu | Circus pygargus |
| All names | Bod teircail | Buteo buteo |
| All names | Bod tinwen | Circus cyaneus |
| All names | Bod tinwyn | Circus cyaneus |
| All names | Bod wennol | Milvus milvus |
| All names | Bod y gwerni | Circus aeruginosus |
| All names | Bod y mêl | Pernis apivorus |
| All names | Bod y wern | Circus aeruginosus |
| All names | Boda (llwyd) | Buteo buteo |
| All names | Boda bacsiog | Buteo lagopus |
| All names | Boda chwiw | Milvus milvus |
| All names | Boda garwgoes | Buteo lagopus |
| All names | Boda Montagu | Circus pygargus |
| All names | Boda tinwyn | Circus cyaneus |
| All names | Boda'r gwerni | Circus aeruginosus |
| All names | Boda'r mêl | Pernis apivorus |
| All names | Bodfforchog | Milvus milvus |
| All names | Boncath | Buteo buteo |
| All names | Bran (fawr) | Corvus corone |
| All names | Bran big coch | Pyrrhocorax pyrrhocorax |
| All names | Brân dyddyn | Corvus corone |
| All names | Bran gernyw | Pyrrhocorax pyrrhocorax |
| All names | Brân goesgoch | Pyrrhocorax pyrrhocorax |
| All names | Bran hedlyd | Corvus cornix |
| All names | Bran lwyd | Corvus cornix |
| All names | Brân lwyd | Corvus cornix |
| All names | Bran syddyn | Corvus corone |
| All names | Bran yr Iwerddon | Corvus cornix |
| All names | Bras bronfelen | Emberiza aureola |
| All names | Bras dulas | Passerina cyanea |
| All names | Bras ffrainc | Emberiza cirlus |
| All names | Bras gwledig | Emberiza rustica |
| All names | Bras lleiaf | Emberiza pusilla |
| All names | Bras melyn | Emberiza citrinella |
| All names | Bras penddu | Emberiza melanocephala |
| All names | Bras y cyrs | Emberiza schoeniclus |
| All names | Bras y gerdi | Emberiza hortulana |
| All names | Bras y gerrdi | Emberiza hortulana |
| All names | Bras y gogledd | Calcarius lapponicus |
| All names | Bras y graig | Emberiza cia |
| All names | Bras yr eira | Plectrophenax nivalis |
| All names | Bras yr ŷd | Emberiza calandra |
| All names | Bras-y-ddruttan | Emberiza calandra |
| All names | Brech y fuches | Motacilla alba |
| All names | Brith y fuches felen | Motacilla flava |
| All names | Brith y fuches lwyd | Motacilla cinerea |
| All names | Brith yr oged | Motacilla alba |
| All names | Bronfraith | Turdus philomelos |
| All names | Bronfraith Carolina | Dumetella carolinensis |
| All names | Bronfraith dywyll | Turdus naumanni |
| All names | Bronfraith fochlwyd | Catharus minimus |
| All names | Bronfraith las y graig | Monticola solitarius |
| All names | Bronfraith y graig | Monticola saxatilis |
| All names | Brongoch | Erithacus rubecula |
| All names | Bronlas | Luscinia svecica |
| All names | Bronlas smotyn coch | Luscinia svecica |
| All names | Bronruddyn | Erithacus rubecula |
| All names | Bronruddyn y mynydd | Fringilla montifringilla |
| All names | Bronwen | Sylvia communis |
| All names | Bronwen leiaf | Sylvia curruca |
| All names | Bronwen y dwr | Cinclus cinclus |
| All names | Bronwen y dŵr | Cinclus cinclus |
| All names | Brych twywll | Turdus naumanni |
| All names | Brych y coed | Turdus viscivorus |
| All names | Brych y graig | Monticola saxatilis |
| All names | Bwmp y gors | Botaurus stellaris |
| All names | Bwncath | Buteo buteo |
| All names | Cambig | Recurvirostra avosetta |
| All names | Carfil bach | Alle alle |
| All names | Cas gan longwr | Hydrobates pelagicus |
| All names | Caseg eira | Turdus pilaris |
| All names | Caseg y ddryccin | Turdus viscivorus |
| All names | Ceiliog coed | Tetrao urogallus |
| All names | Ceiliog ddu | Tetrao tetrix |
| All names | Ceiliog y coed | Phasianus colchicus |
| All names | Ceiliog y mynydd (m) | Lagopus lagopus |
| All names | Ceiliog y waun | Otis tarda |
| All names | Ceiliog y waun lleiaf | Tetrax tetrax |
| All names | Cethlyth (Y) | Cuculus canorus |
| All names | Chwibanydd | Pyrrhula pyrrhula |
| All names | Chwilgorn y mynydd | Pluvialis apricaria |
| All names | Chwilog | Uria aalge |
| All names | Chwiw | Anas penelope |
| All names | Chwiwell | Anas penelope |
| All names | Chwiwell America | Anas americana |
| All names | Chwybanydd | Pyrrhula pyrrhula |
| All names | Ciach fawr | Gallinago media |
| All names | Ciconia du | Ciconia nigra |
| All names | Ciconia gwyn | Ciconia ciconia |
| All names | Cigfran | Corvus corax |
| All names | Cigydd cefngoch | Lanius collurio |
| All names | Cigydd glas | Lanius minor |
| All names | Cigydd gwdw | Lanius isabellinus |
| All names | Cigydd gwelw | Lanius isabellinus |
| All names | Cigydd mawr | Lanius excubitor |
| All names | Cigydd pengoch | Lanius senator |
| All names | Clef y garreg | Saxicola rubicola |
| All names | Clef yr eithin | Saxicola rubetra |
| All names | Clochdar cerrig | Saxicola rubicola |
| All names | Clochdar eithin | Saxicola rubetra |
| All names | Clochdar Siberia | Anthus gustavi |
| All names | Clochdar y cerrig | Saxicola rubicola |
| All names | Clochder y cerrig | Saxicola rubicola |
| All names | Clochder y mynydd | Ficedula hypoleuca |
| All names | Clochder yr eithin | Saxicola rubetra |
| All names | Cnocell brith | Dendrocopos major |
| All names | Cnocell brith bach | Dendrocopos minor |
| All names | Cnocell fraith fwyaf | Dendrocopos major |
| All names | Cnocell fraith leiaf | Dendrocopos minor |
| All names | Cnocell werdd | Picus viridis |
| All names | Cnocell y cnau | Sitta europaea |
| All names | Cnut | Calidris canutus |
| All names | Coblyn lleiaf | Dendrocopos minor |
| All names | Coblyn mwyaf | Dendrocopos major |
| All names | Coblyn-y-coed | Picus viridis |
| All names | Coch dan-aden | Turdus iliacus |
| All names | Coch y berllan | Pyrrhula pyrrhula |
| All names | Coch y grug | Lagopus lagopus |
| All names | Cochiad | Lagopus lagopus |
| All names | Coeg gylfinhir | Numenius phaeopus |
| All names | Coegfran | Corvus monedula |
| All names | Coegyfinir | Numenius phaeopus |
| All names | Coegyfinir bach | Numenius minutus |
| All names | Coegylfinir | Numenius phaeopus |
| All names | Coegylfinir bach | Numenius minutus |
| All names | Coesgoch | Tringa totanus |
| All names | Coeswerdd | Tringa nebularia |
| All names | Cog | Cuculus canorus |
| All names | Côg | Cuculus canorus |
| All names | Cog bigfelen | Coccyzus americanus |
| All names | Cog frech | Clamator glandarius |
| All names | Colomen ddof | Columba oenas |
| All names | Colomen fair | Streptopelia turtur |
| All names | Colomen goed | Columba palumbus |
| All names | Colomen wyllt | Columba livia domestica |
| All names | Colomen wyllt | Columba oenas |
| All names | Colomen y graig | Columba livia |
| All names | Colomen y penrhyn | Daption capense |
| All names | Comchwiglen | Vanellus vanellus |
| All names | Copog | Upupa epops |
| All names | Cor-iar | Perdix perdix |
| All names | Corfonfraith | Catharus ustulatus |
| All names | Corfran | Corvus monedula |
| All names | Corfronfraith | Catharus ustulatus |
| All names | Corgwalch | Falco columbarius |
| All names | Corgwtiad aur | Pluvialis dominica |
| All names | Corgwtiad y Môr Tawel | Pluvialis fulva |
| All names | Corhedydd cefnwyrdd | Anthus hodgsoni |
| All names | Corhedydd gwyrddgefn | Anthus hodgsoni |
| All names | Corhedydd gyddfgoch | Anthus cervinus |
| All names | Corhedydd melyn | Anthus campestris |
| All names | Corhedydd Richard | Anthus richardi |
| All names | Corhedydd y coed | Anthus trivialis |
| All names | Corhedydd y dwr | Anthus spinoletta |
| All names | Corhedydd y dŵr | Anthus spinoletta |
| All names | Corhedydd y graig | Anthus petrosus |
| All names | Corhedydd y waun | Anthus pratensis |
| All names | Corhwyaden | Anas carolinensis |
| All names | Corhwyaden | Anas crecca |
| All names | Coriar yr albin | Lagopus muta |
| All names | Corn y wich | Vanellus vanellus |
| All names | Cornchwiglen | Vanellus vanellus |
| All names | Cornicyll | Vanellus vanellus |
| All names | Cornicyll cadwynog | Charadrius hiaticula |
| All names | Cornicyll llwyd | Pluvialis squatarola |
| All names | Cornicyll y gors | Vanellus vanellus |
| All names | Cornicyll y mynydd | Pluvialis apricaria |
| All names | Cornicyll y waen | Vanellus vanellus |
| All names | Cornor y gwennydd | Vanellus vanellus |
| All names | Cors hwyad | Anas platyrhynchos |
| All names | Corshwyad ddu | Fulica atra |
| All names | Corswennol adeinwen | Chlidonias leucopterus |
| All names | Corswennol ddu | Chlidonias niger |
| All names | Corswennol farfog | Chlidonias hybrida |
| All names | Crec penddu'r eithin | Saxicola rubicola |
| All names | Crec y garreg | Saxicola rubicola |
| All names | Crec yr eithin | Saxicola rubetra |
| All names | Creyr bach | Egretta garzetta |
| All names | Crëyr bach | Egretta garzetta |
| All names | Crêyr glas | Ardea cinerea |
| All names | Crëyr glas | Ardea cinerea |
| All names | Creyr mawr gwyn | Ardea alba |
| All names | Crëyr mawr gwyn | Ardea alba |
| All names | Crêyr melyn | Ardeola ralloides |
| All names | Crëyr melyn | Ardeola ralloides |
| All names | Crêyr porffor | Ardea purpurea |
| All names | Crëyr porffor | Ardea purpurea |
| All names | Crëyr y gwartheg | Bubulcus ibis |
| All names | Crêyr y nos | Nycticorax nycticorax |
| All names | Crëyr y nos | Nycticorax nycticorax |
| All names | Croesbig fawr | Loxia pytyopsittacus |
| All names | Croesbig wenaden | Loxia leucoptera |
| All names | Cropiedydd | Certhia familiaris |
| All names | Crymanbig ddu | Plegadis falcinellus |
| All names | Cudyll bach | Falco columbarius |
| All names | Cudyll coch | Falco tinnunculus |
| All names | Cudyll coch lleiaf | Falco naumanni |
| All names | Cudyll glas | Falco peregrinus |
| All names | Cudyll glas bach | Falco columbarius |
| All names | Cudyll troedgoch | Falco amurensis |
| All names | Cudyll troedgoch | Falco vespertinus |
| All names | Cudyll y gwynt | Falco tinnunculus |
| All names | Cwtaiar | Fulica atra |
| All names | Cwtaid y traeth | Arenaria interpres |
| All names | Cwtair | Fulica atra |
| All names | Cwtiad aur | Pluvialis apricaria |
| All names | Cwtiad Caint | Charadrius alexandrinus |
| All names | Cwtiad heidiol | Vanellus gregarius |
| All names | Cwtiad llwyd | Pluvialis squatarola |
| All names | Cwtiad torchog | Charadrius hiaticula |
| All names | Cwtiad torchog bach | Charadrius dubius |
| All names | Cwtiad torchog macor | Charadrius vociferus |
| All names | Cwtiad torchog mawr | Charadrius vociferus |
| All names | Cwtiad y traeth | Arenaria interpres |
| All names | Cwtiad y tywod mwyaf | Charadrius leschenaultii |
| All names | Cwtiad y tywod mwyalf | Charadrius leschenaultii |
| All names | Cwtiadwennol aden-ddu | Glareola nordmanni |
| All names | Cwtiadwennol dorchog | Glareola pratincola |
| All names | Cwtiar | Fulica atra |
| All names | Cwtyn aur | Pluvialis apricaria |
| All names | Cwtyn ddu | Limosa limosa |
| All names | Cwtyn llwyd | Burhinus oedicnemus |
| All names | Cwtyn modewyog | Charadrius hiaticula |
| All names | Cwtyn yr aur | Pluvialis apricaria |
| All names | Cyffylog | Scolopax rusticola |
| All names | Cyffylog y mor | Limosa lapponica |
| All names | Cylionydd | Muscicapa striata |
| All names | Cynffon sidan | Bombycilla garrulus |
| All names | Cynffonwen | Oenanthe oenanthe |
| All names | Ddreiniog | Carduelis spinus |
| All names | Delor fraith | Dendrocopos major |
| All names | Delor fraith leiaf | Dendrocopos minor |
| All names | Delor y cnau | Sitta europaea |
| All names | Delor y drew | Picus viridis |
| All names | Deryn coch y fflam | Phoenicurus phoenicurus |
| All names | Deryn du'r llan | Apus apus |
| All names | Dinboeth (Y) | Phoenicurus phoenicurus |
| All names | Dreiniog | Carduelis spinus |
| All names | Dreydwen | Sturnus vulgaris |
| All names | Dringedydd bach | Certhia familiaris |
| All names | Dringwr bach | Certhia familiaris |
| All names | Drudwen | Sturnus vulgaris |
| All names | Drudwen wridog | Pastor roseus |
| All names | Drydwy (Y) | Sturnus vulgaris |
| All names | Dryw | Troglodytes troglodytes |
| All names | Dryw bach | Troglodytes troglodytes |
| All names | Dryw bach y coed | Regulus regulus |
| All names | Dryw bach y ddaear | Phylloscopus trochilus |
| All names | Dryw ben aur | Regulus regulus |
| All names | Dryw ben felen | Regulus regulus |
| All names | Dryw eurben | Regulus regulus |
| All names | Dryw felen | Phylloscopus collybita |
| All names | Dryw felen | Phylloscopus sibilatrix |
| All names | Dryw felen | Phylloscopus trochilus |
| All names | Dryw penfflamgoch | Regulus ignicapilla |
| All names | Dryw'r coed | Phylloscopus sibilatrix |
| All names | Dryw'r ddaear | Phylloscopus sibilatrix |
| All names | Dryw'r drysni | Sylvia communis |
| All names | Dryw'r helyg | Phylloscopus trochilus |
| All names | Dryw'r hesg | Acrocephalus schoenobaenus |
| All names | Dryw'r wen | Sylvia borin |
| All names | Dryw'r wen | Sylvia communis |
| All names | Dylluan felynddu | Strix aluco |
| All names | Dylluan fig | Strix aluco |
| All names | Dylluan frech | Strix aluco |
| All names | Dylluan glustiog | Asio flammeus |
| All names | Dylluan gorniog | Asio otus |
| All names | Dylluan rudd | Strix aluco |
| All names | Dylluan wen | Tyto alba |
| All names | Dylluan y coed | Strix aluco |
| All names | Eclysen | Branta leucopsis |
| All names | Ehedydd | Alauda arvensis |
| All names | Ehedydd bach | Anthus pratensis |
| All names | Ehedydd bach | Anthus spinoletta |
| All names | Ehedydd bach | Anthus petrosus |
| All names | Ehedydd copog | Galerida cristata |
| All names | Ehedydd du | Melanocorypha yeltoniensis |
| All names | Ehedydd y coed | Anthus trivialis |
| All names | Ehedydd y coed | Lullula arborea |
| All names | Ehedydd y traeth | Eremophila alpestris |
| All names | Ehedydd y treath | Eremophila alpestris |
| All names | Elrck | Cygnus cygnus |
| All names | Eos | Luscinia megarhynchos |
| All names | Eos fronfraith | Luscinia luscinia |
| All names | Eryr cynffon wen | Haliaeetus albicilla |
| All names | Eryr euraid | Aquila chrysaetos |
| All names | Eryr euraidd | Aquila chrysaetos |
| All names | Eryr melyn | Aquila chrysaetos |
| All names | Eryr moel | Haliaeetus leucocephalus |
| All names | Eryr tinwyn | Haliaeetus albicilla |
| All names | Eryr y dwr | Pandion haliaetus |
| All names | Eryr y môr | Haliaeetus albicilla |
| All names | Eryr y mor | Pandion haliaetus |
| All names | Euryn | Oriolus oriolus |
| All names | Euryn Baltimore | Icterus galbula |
| All names | Euryn y gogledd | Icterus galbula |
| All names | Euryn yr haf | Piranga rubra |
| All names | Ffesant | Phasianus colchicus |
| All names | Ffesant Amherst | Chrysolophus amherstiae |
| All names | Ffesant euraid | Chrysolophus pictus |
| All names | Ffigysog | Sylvia borin |
| All names | For hwyad ddu (Y) | Melanitta nigra |
| All names | Fronfraith | Turdus philomelos |
| All names | Fronfraith fawr | Turdus viscivorus |
| All names | Fulfran leiaf | Phalacrocorax aristotelis |
| All names | Gafr y gors | Gallinago gallinago |
| All names | Gan(s) | Morus bassanus |
| All names | Garan | Grus grus |
| All names | Garan hwyad | Anas platyrhynchos |
| All names | Gegid | Carduelis chloris |
| All names | Gîach (myniar) | Gallinago gallinago |
| All names | Gîach fach | Lymnocryptes minimus |
| All names | Gïach fach | Lymnocryptes minimus |
| All names | Gïach fawr | Gallinago media |
| All names | Gîach gyffredin | Gallinago gallinago |
| All names | Gïach gyffredin | Gallinago gallinago |
| All names | Giach gylfin-hir | Limnodromus scolopaceus |
| All names | Gïach gylfin-hir | Limnodromus scolopaceus |
| All names | Gigfran fawr | Corvus corax |
| All names | Glas y dorlan | Alcedo atthis |
| All names | Golfan | Passer domesticus |
| All names | Golfan tingoch | Carduelis flavirostris |
| All names | Golfan y mynydd | Passer montanus |
| All names | Golfan-y-gors | Emberiza schoeniclus |
| All names | Golfan-yr-eira | Plectrophenax nivalis |
| All names | Goppog | Upupa epops |
| All names | Grepianog | Certhia familiaris |
| All names | Grugiag Ddu | Tetrao tetrix |
| All names | Grugiar | Lagopus lagopus |
| All names | Grugiar ddu | Tetrao tetrix |
| All names | Grugiar yr alban | Lagopus lagopus |
| All names | Gwalch glas | Accipiter nisus |
| All names | Gwalch marth | Accipiter gentilis |
| All names | Gwalch y nos | Caprimulgus europaeus |
| All names | Gwalch y penweig | Alca torda |
| All names | Gwalch y pysgod | Pandion haliaetus |
| All names | Gwalch y weilgi | Pandion haliaetus |
| All names | Gwas y gog | Anthus pratensis |
| All names | Gwas y gog | Jynx torquilla |
| All names | Gwas y Seibi | Carduelis carduelis |
| All names | Gwddfgam | Jynx torquilla |
| All names | Gwddfgwyn | Sylvia communis |
| All names | Gwddfro | Anthus pratensis |
| All names | Gwddfro | Jynx torquilla |
| All names | Gweipa | Accipiter nisus |
| All names | Gwenfol | Hirundo rustica |
| All names | Gwennol | Hirundo rustica |
| All names | Gwennol ddu | Apus apus |
| All names | Gwennol ddu delw | Apus pallidus |
| All names | Gwennol ddu fach | Apus affinis |
| All names | Gwennol ddu'r alpan | Tachymarptis melba |
| All names | Gwennol ddu'r Alpau | Tachymarptis melba |
| All names | Gwennol ddu'r simneiau | Chaetura pelagica |
| All names | Gwennol dingoch | Cecropis daurica |
| All names | Gwennol welw-ddu | Apus pallidus |
| All names | Gwennol y bargod | Delichon urbicum |
| All names | Gwennol y bondo | Delichon urbicum |
| All names | Gwennol y clogwyn | Ptyonoprogne rupestris |
| All names | Gwennol y glennydd | Riparia riparia |
| All names | Gwennol-y-môr | Sterna hirundo |
| All names | Gwich hedydd | Locustella naevia |
| All names | Gwilym | Uria aalge |
| All names | Gwilym ddu | Cepphus grylle |
| All names | Gwipa | Accipiter nisus |
| All names | Gwipal | Accipiter nisus |
| All names | Gwyach | Podiceps |
| All names | Gwyach fach | Tachybaptus ruficollis |
| All names | Gwyach fawr gopog | Podiceps cristatus |
| All names | Gwyach gorniog | Podiceps auritus |
| All names | Gwyach gyddfddu | Podiceps nigricollis |
| All names | Gwyach gyddfgoch | Podiceps grisegena |
| All names | Gwyach gylfinfraith | Podilymbus podiceps |
| All names | Gwyach yddfddu | Podiceps nigricollis |
| All names | Gwyach yddfgoch | Podiceps grisegena |
| All names | Gwyach ylfinfraith | Podilymbus podiceps |
| All names | Gwybedog | Muscicapa striata |
| All names | Gwybedog brith | Ficedula hypoleuca |
| All names | Gwybedog brongoch | Ficedula parva |
| All names | Gwybedog ddu a gwyn | Muscicapa striata |
| All names | Gwybedog mannog | Muscicapa striata |
| All names | Gwybedog torchog | Ficedula albicollis |
| All names | Gwybedog y gwenyn | Merops apiaster |
| All names | Gwydd bonar | Anser fabalis |
| All names | Gŵydd Canada | Branta canadensis |
| All names | Gwydd dalcen gwyn | Anser albifrons |
| All names | Gŵydd dalcen-wen | Anser albifrons |
| All names | Gŵydd dalcen-wen leiaf | Anser erythropus |
| All names | Gŵydd ddu | Branta bernicla |
| All names | Gŵydd droedbinc | Anser brachyrhynchus |
| All names | Gŵydd frongoch | Branta ruficollis |
| All names | Gŵydd wyllt | Anser anser |
| All names | Gŵydd wyran | Branta leucopsis |
| All names | Gŵydd y llafur | Anser fabalis |
| All names | Gŵydd yr Aifft | Alopochen aegyptiaca |
| All names | Gŵydd yr eira | Chen caerulescens |
| All names | Gŵydd yr eira | Anser caerulescens |
| All names | Gwylan | Larus |
| All names | Gwylan benddu | Larus ridibundus |
| All names | Gwylan bigfain | Larus genei |
| All names | Gwylan Bonaparte | Larus philadelphia |
| All names | Gwylan chwerthinog | Larus atricilla |
| All names | Gwylan fechan | Larus minutus |
| All names | Gwylan fodrwybig | Larus delawarensis |
| All names | Gwylan Franklin | Larus pipixcan |
| All names | Gwylan gefnddu fwyaf | Larus marinus |
| All names | Gwylan gefnddu leiaf | Larus fuscus |
| All names | Gwylan gefnddu lleiaf | Larus fuscus |
| All names | Gwylan goesddu | Rissa tridactyla |
| All names | Gwylan goesfelen | Larus cachinnans |
| All names | Gwylan goesfelen | Larus michahellis |
| All names | Gwylan ifori | Pagophila eburnea |
| All names | Gwylan mor y canoldir | Larus melanocephalus |
| All names | Gwylan Môr y Canoldir | Larus melanocephalus |
| All names | Gwylan Ross | Rhodostethia rosea |
| All names | Gwylan Sabine | Xema sabini |
| All names | Gwylan y gogledd | Larus hyperboreus |
| All names | Gwylan y Gweunydd | Larus canus |
| All names | Gwylan y penwaig | Larus argentatus |
| All names | Gwylan yr Arctig | Larus glaucoides |
| All names | Gwylog | Uria aalge |
| All names | Gwylog ddu | Cepphus grylle |
| All names | Gyddfwyn robin goch | Irania gutturalis |
| All names | Gyfinbraff | Coccothraustes coccothraustes |
| All names | Gylfin groes | Loxia curvirostra |
| All names | Gylfinbraff | Coccothraustes coccothraustes |
| All names | Gylfindew brongoch | Pheucticus ludovicianus |
| All names | Gylfinir | Numenius arquata |
| All names | Gylfinir escimo | Numenius borealis |
| All names | Hebog chwyldro | Falco rusticolus |
| All names | Hebog dramor | Falco peregrinus |
| All names | Hebog llywydlâs (m) | Circus cyaneus |
| All names | Hebog marthin | Accipiter gentilis |
| All names | Hebog tramor | Falco peregrinus |
| All names | Hebog y gogledd | Falco rusticolus |
| All names | Hebog yr ehedydd | Falco subbuteo |
| All names | Hebog yr hedydd | Falco subbuteo |
| All names | Hedydd | Alauda arvensis |
| All names | Hedydd y coed | Lullula arborea |
| All names | Hirgoes | Himantopus himantopus |
| All names | Hobigoch brongoch (Yr) | Erithacus rubecula |
| All names | Hugan | Morus bassanus |
| All names | Hutan (y mynydd) | Charadrius morinellus |
| All names | Hutan y mynydd | Charadrius morinellus |
| All names | Hutan-y-môr | Arenaria interpres |
| All names | Hutan-y-môr | Charadrius hiaticula |
| All names | Hwyad bengoch | Aythya ferina |
| All names | Hwyad felfedog | Melanitta fusca |
| All names | Hwyaden addfain | Anas querquedula |
| All names | Hwyaden asgell-las | Anas discors |
| All names | Hwyaden benddu | Aythya marila |
| All names | Hwyaden bengoch | Aythya ferina |
| All names | Hwyaden bengoch America | Aythya americana |
| All names | Hwyaden ddanheddog | Mergus merganser |
| All names | Hwyaden ddu | Anas rubripes |
| All names | Hwyaden ddu | Melanitta nigra |
| All names | Hwyaden dorchag | Aythya collaris |
| All names | Hwyaden dorchog | Aythya collaris |
| All names | Hwyaden frongoch | Mergus serrator |
| All names | Hwyaden fwythblu | Somateria mollissima |
| All names | Hwyaden fwythblu'r gogledd | Somateria spectabilis |
| All names | Hwyaden goch | Oxyura jamaicensis |
| All names | Hwyaden goch yr eithin | Tadorna ferruginea |
| All names | Hwyaden gopog | Aythya fuligula |
| All names | Hwyaden gopynog | Aythya fuligula |
| All names | Hwyaden gribgoch | Netta rufina |
| All names | Hwyaden gribog | Aix galericulata |
| All names | Hwyaden gynffon-hir | Clangula hyemalis |
| All names | Hwyaden lostfain | Anas acuta |
| All names | Hwyaden lwyd | Anas strepera |
| All names | Hwyaden lydanbig | Anas clypeata |
| All names | Hwyaden lygad arian | Aythya marila |
| All names | Hwyaden lygad-aur | Bucephala clangula |
| All names | Hwyaden lygadwen | Aythya nyroca |
| All names | Hwyaden wyllt | Anas platyrhynchos |
| All names | Hwyaden y coed | Aix sponsa |
| All names | Hwyaden yr eithin | Tadorna tadorna |
| All names | Hwyadwydd gyffredin | Mergus merganser |
| All names | Iâr ddŵfr foel | Fulica atra |
| All names | Iâr ddŵr | Gallinula chloropus |
| All names | Iâr goch | Lagopus lagopus |
| All names | Iâr goch | Lagopus lagopus scoticus |
| All names | Iâr goed | Phasianus colchicus |
| All names | Iâr y diffeithwch | Syrrhaptes paradoxus |
| All names | Jac-y-do | Corvus monedula |
| All names | Ji-binc | Fringilla coelebs |
| All names | Junco llygeitu | Junco hyemalis |
| All names | Jynco llwyd | Junco hyemalis |
| All names | Kedydd yr helvyg | Acrocephalus schoenobaenus |
| All names | Linbengoch | Carduelis flammea |
| All names | Lleian | Parus major |
| All names | Lleian gynffon hir | Aegithalos caudatus |
| All names | Lleian wen | Mergellus albellus |
| All names | Llinos | Carduelis cannabina |
| All names | Llinos bengoch | Carduelis flammea |
| All names | Llinos bengoch gyffredin | Carduelis flammea |
| All names | Llinos bengoch yr Arctig | Carduelis hornemanni |
| All names | Llinos felen | Emberiza citrinella |
| All names | Llinos frech | Serinus serinus |
| All names | Llinos goch | Carpodacus erythrinus |
| All names | Llinos werdd | Carduelis chloris |
| All names | Llinos y mynydd | Carduelis flavirostris |
| All names | Llostruddyn | Phoenicurus phoenicurus |
| All names | Llurs | Alca torda |
| All names | Llurs(en) | Alca torda |
| All names | Llwybig | Platalea leucorodia |
| All names | Llwyd bach | Prunella modularis |
| All names | Llwyd gyddfwyn | Zonotrichia albicollis |
| All names | Llwyd persain | Melospiza melodia |
| All names | Llwyd y berth | Prunella modularis |
| All names | Llwyd y gors | Acrocephalus schoenobaenus |
| All names | Llwyd y gwrych | Prunella modularis |
| All names | Llwyd y mynydd | Prunella collaris |
| All names | Llwyd y tywod | Calidris alba |
| All names | Llwyd yr hesg | Acrocephalus schoenobaenus |
| All names | Llwydfron | Sylvia communis |
| All names | Llwydfron fach | Sylvia curruca |
| All names | Llydandroed gyddfgoch | Phalaropus lobatus |
| All names | Llydandroed llwyd | Phalaropus fulicarius |
| All names | Llydandroed Wilson | Phalaropus tricolor |
| All names | Mae'r frân lwyd | Corvus cornix |
| All names | Malwr cnau | Nucifraga caryocatactes |
| All names | Marthin ddu | Apus apus |
| All names | Marthin penbwl | Delichon urbicum |
| All names | Melyngoes bach | Tringa flavipes |
| All names | Melyngoes mawr | Tringa melanoleuca |
| All names | Merwys | Turdus merula |
| All names | Milfran | Corvus corone |
| All names | Mor eryr | Haliaeetus albicilla |
| All names | Môr-hwyaden America | Melanitta nigra |
| All names | Môr-hwyaden ddu | Melanitta nigra |
| All names | Môr-hwyaden y gogledd | Melanitta fusca |
| All names | Môr-hwyaden yr ewyn | Melanitta perspicillata |
| All names | Morfran | Phalacrocorax carbo |
| All names | Morfran gopog | Phalacrocorax aristotelis |
| All names | Morfran werdd | Phalacrocorax aristotelis |
| All names | Morwennol | Sterna |
| All names | Morwennol bigddu | Thalasseus sandvicensis |
| All names | Morwennol ddu | Chlidonias niger |
| All names | Morwennol fach | Sterna paradisaea |
| All names | Morwennol fawr | Thalasseus maximus |
| All names | Morwennol fechan | Sternula albifrons |
| All names | Morwennol ffrwynog | Onychoprion anaethetus |
| All names | Morwennol Forster | Sterna forsteri |
| All names | Morwennol fraith | Onychoprion fuscatus |
| All names | Morwennol fwyaf | Hydroprogne caspia |
| All names | Morwennol gribog leiaf | Thalasseus bengalensis |
| All names | Morwennol gyffredin | Sterna hirundo |
| All names | Morwennol wridog | Sterna dougallii |
| All names | Morwennol y gogledd | Stercorarius parasiticus |
| All names | Morwennol y gogledd | Sterna paradisaea |
| All names | Morwennol ylfinbraff | Gelochelidon nilotica |
| All names | Mulfran | Phalacrocorax carbo |
| All names | Mulfran gopog | Phalacrocorax aristotelis |
| All names | Mulfran wen | Morus bassanus |
| All names | Mulfran werdd | Phalacrocorax aristotelis |
| All names | Mwyalchen | Turdus merula |
| All names | Mwyalchen ddwr | Cinclus cinclus |
| All names | Mwyalchen y graig | Turdus torquatus |
| All names | Mwyalchen y mynydd | Turdus torquatus |
| All names | Myniar ciaf | Lymnocryptes minimus |
| All names | Nico | Carduelis carduelis |
| All names | Nico, (Jack) | Carduelis carduelis |
| All names | Nicol | Carduelis carduelis |
| All names | Pâl | Fratercula arctica |
| All names | Paracit torchog | Psittacula krameri |
| All names | Pedryn Bulwer | Bulweria bulwerii |
| All names | Pedryn cynffon-fforchog | Oceanodroma leucorhoa |
| All names | Pedryn drycin | Hydrobates pelagicus |
| All names | Pedryn gynffon-fforchog | Oceanodroma leucorhoa |
| All names | Pedryn meddal blu | Pterodroma mollis |
| All names | Pedryn torchog | Pterodroma leucoptera |
| All names | Pedryn Wilson | Oceanites oceanicus |
| All names | Pelican gwyn | Pelecanus onocrotalus |
| All names | Penddu | Sylvia atricapilla |
| All names | Pendew | Coccothraustes coccothraustes |
| All names | Pengam | Jynx torquilla |
| All names | Pengoch | Carduelis flammea |
| All names | Penloyn | Periparus ater |
| All names | Penloyn | Parus major |
| All names | Penloyn-y-gors | Poecile palustris |
| All names | Petrisen | Perdix perdix |
| All names | Petrisen goesgoch | Alectoris rufa |
| All names | Pia | Pica pica |
| All names | Pibydd bach | Calidris minuta |
| All names | Pibydd Baird | Calidris bairdii |
| All names | Pibydd bronllwyd | Tryngites subruficollis |
| All names | Pibydd brych | Actitis macularius |
| All names | Pibydd cain | Calidris melanotos |
| All names | Pibydd cambig | Calidris ferruginea |
| All names | Pibydd coesgoch | Tringa totanus |
| All names | Pibydd coesgoch mannog | Tringa erythropus |
| All names | Pibydd coesgogh mannog | Tringa erythropus |
| All names | Pibydd coeswerdd | Tringa nebularia |
| All names | Pibydd cynffon-hir | Bartramia longicauda |
| All names | Pibydd cynffonir | Bartramia longicauda |
| All names | Pibydd cynffonlwyd | Tringa brevipes |
| All names | Pibydd du | Calidris maritima |
| All names | Pibydd gwyrdd | Tringa ochropus |
| All names | Pibydd gynffonfain | Calidris acuminata |
| All names | Pibydd gynffonlwd | Tringa brevipes |
| All names | Pibydd lleiaf | Calidris minuta |
| All names | Pibydd lleiaf | Calidris minutilla |
| All names | Pibydd llwyd | Calidris pusilla |
| All names | Pibydd llydanbig | Limicola falcinellus |
| All names | Pibydd llydandroed | Phalaropus fulicarius |
| All names | Pibydd rhuddgoch | Calidris alpina |
| All names | Pibydd Temminck | Calidris temminckii |
| All names | Pibydd tinwen | Calidris fuscicollis |
| All names | Pibydd torchog | Philomachus pugnax |
| All names | Pibydd y dorlan | Actitis hypoleucos |
| All names | Pibydd y gors | Tringa stagnatilis |
| All names | Pibydd y graean | Tringa glareola |
| All names | Pibydd y mawn | Calidris alpina |
| All names | Pibydd y traeth | Actitis hypoleucos |
| All names | Pibydd y traeth | Calidris alba |
| All names | Pibydd y tywod | Calidris alba |
| All names | Pibydd yr aber | Calidris canutus |
| All names | Pig mynawd | Recurvirostra avosetta |
| All names | Pila gwyrdd | Carduelis spinus |
| All names | Pinc y mynydd | Fringilla montifringilla |
| All names | Pioden | Pica pica |
| All names | Pioden y môr | Haematopus ostralegus |
| All names | Piogen | Pica pica |
| All names | Piogen goch | Garrulus glandarius |
| All names | Piogen y môr | Haematopus ostralegus |
| All names | Piogen-y-coed | Garrulus glandarius |
| All names | Pwffin | Fratercula arctica |
| All names | Pwffin manaw | Puffinus puffinus |
| All names | Pwffingen fanaw | Puffinus puffinus |
| All names | Pysg eryr | Pandion haliaetus |
| All names | Pysgotwr | Alcedo atthis |
| All names | Rhedwr y moelydd | Burhinus oedicnemus |
| All names | Rhedwr y twyni | Cursorius cursor |
| All names | Rhegen Baillon | Porzana pusilla |
| All names | Rhegen fach | Porzana parva |
| All names | Rhegen fraith | Porzana porzana |
| All names | Rhegen sora | Porzana carolina |
| All names | Rhegen y dŵr | Rallus aquaticus |
| All names | Rhegen yr ŷd | Crex crex |
| All names | Rhegen-yr-ŷd | Crex crex |
| All names | Rholydd | Coracias garrulus |
| All names | Rhonell goch | Phoenicurus phoenicurus |
| All names | Rhostog coch | Limosa lapponica |
| All names | Rhostog gynffonddu | Limosa limosa |
| All names | Rhostog gynffonfrith | Limosa lapponica |
| All names | Robin goch | Erithacus rubecula |
| All names | Robin gyddfwyn | Irania gutturalis |
| All names | Sgiwen fawr | Stercorarius skua |
| All names | Sgiwen frech | Stercorarius pomarinus |
| All names | Sgiwen lostfain | Stercorarius longicaudus |
| All names | Sgiwen y gogledd | Stercorarius parasiticus |
| All names | Sidangynffon | Bombycilla garrulus |
| All names | Siff-saff | Phylloscopus collybita |
| All names | Sigldigwt | Motacilla alba |
| All names | Siglen felen | Motacilla flava |
| All names | Siglen fraith | Motacilla alba |
| All names | Siglen llwyd | Motacilla cinerea |
| All names | Siglen lwyd | Motacilla cinerea |
| All names | Siglen wen | Motacilla alba |
| All names | Siglen wen (Y) | Motacilla alba |
| All names | Socan eira | Turdus pilaris |
| All names | Sofliar | Coturnix coturnix |
| All names | Sywider | Phylloscopus trochilus |
| All names | Telor aelfelen | Phylloscopus humei |
| All names | Telor aelfelen | Phylloscopus inornatus |
| All names | Telor aur | Hippolais icterina |
| All names | Telor Blackburn | Dendroica fusca |
| All names | Telor Blackburnian | Dendroica fusca |
| All names | Telor Bonelli | Phylloscopus bonelli |
| All names | Telor Bonelli y gorllewin | Phylloscopus bonelli |
| All names | Telor brith | Mniotilta varia |
| All names | Telor brongoch | Sylvia cantillans |
| All names | Telor Cetti | Cettia cetti |
| All names | Telor Dartford | Sylvia undata |
| All names | Telor gwaywog | Locustella lanceolata |
| All names | Telor gwyrdd | Phylloscopus trochiloides |
| All names | Telor llwyd | Hippolais pallida |
| All names | Telor llwyd y dwyrain | Hippolais pallida |
| All names | Telor llygatgoch | Vireo olivaceus |
| All names | Telor mawr y cyrs | Acrocephalus arundinaceus |
| All names | Telor melyn | Dendroica petechia |
| All names | Telor melyn | Vireo olivaceus |
| All names | Telor Pallas | Phylloscopus proregulus |
| All names | Telor penddu | Sylvia atricapilla |
| All names | Telor pêr | Hippolais polyglotta |
| All names | Telor Radde | Phylloscopus schwarzi |
| All names | Telor rhesog | Sylvia nisoria |
| All names | Telor Sardinia | Sylvia melanocephala |
| All names | Telor Savi | Locustella luscinioides |
| All names | Telor tinwen | Dendroica striata |
| All names | Telor tywyll | Phylloscopus fuscatus |
| All names | Telor wawr y cyrs | Acrocephalus arundinaceus |
| All names | Telor y afon | Locustella fluviatilis |
| All names | Telor y ardd | Sylvia borin |
| All names | Telor y coed | Phylloscopus sibilatrix |
| All names | Telor y cyrs | Acrocephalus scirpaceus |
| All names | Telor y dwr | Acrocephalus paludicola |
| All names | Telor y dŵr | Acrocephalus paludicola |
| All names | Telor y gwerni | Acrocephalus palustris |
| All names | Telor y twerni | Acrocephalus palustris |
| All names | Telor yr afon | Locustella fluviatilis |
| All names | Telor yr Arctig | Phylloscopus borealis |
| All names | Telor yr ardd | Sylvia borin |
| All names | Telor yr helyg | Phylloscopus trochilus |
| All names | Telor yr hesg | Acrocephalus schoenobaenus |
| All names | Tingoch | Phoenicurus phoenicurus |
| All names | Tingoch du | Phoenicurus ochruros |
| All names | Tingoch Moussier | Phoenicurus moussieri |
| All names | Tinsigl (y gwys) | Motacilla alba |
| All names | Tinsigl felen | Motacilla flava |
| All names | Tinsigl lwyd | Motacilla cinerea |
| All names | Tinwen clustiog du | Oenanthe hispanica |
| All names | Tinwen fraith | Oenanthe pleschanka |
| All names | Tinwen glustiog du | Oenanthe hispanica |
| All names | Tinwen y diffaethwch | Oenanthe deserti |
| All names | Tinwen y garn | Oenanthe oenanthe |
| All names | Tinwen y garreg | Oenanthe oenanthe |
| All names | Titw barfog | Panurus biarmicus |
| All names | Titw cynffon-hir | Aegithalos caudatus |
| All names | Titw gynffon-hir | Aegithalos caudatus |
| All names | Titw mawr | Parus major |
| All names | Titw penddu | Periparus ater |
| All names | Titw pendil | Remiz pendulinus |
| All names | Titw Tomas las | Cyanistes caeruleus |
| All names | Titw tomos las | Cyanistes caeruleus |
| All names | Titw'r helyg | Poecile montana |
| All names | Titw'r wern | Poecile palustris |
| All names | Tresglen | Turdus viscivorus |
| All names | Tresglen goch | Turdus iliacus |
| All names | Trochwr y llyn | Cinclus cinclus |
| All names | Trochydd brongoch (Y) | Mergus serrator |
| All names | Trochydd gyddfddu | Gavia arctica |
| All names | Trochydd gyddfgoch | Gavia stellata |
| All names | Trochydd gyddfoch | Gavia stellata |
| All names | Trochydd mawr | Gavia immer |
| All names | Trochydd pigwen | Gavia adamsii |
| All names | Troellwr bach | Locustella naevia |
| All names | Troellwr mawr | Caprimulgus europaeus |
| All names | Turtur | Streptopelia turtur |
| All names | Turtur dorchog | Streptopelia decaocto |
| All names | Tylluan fach | Athene noctua |
| All names | Tylluan frech | Strix aluco |
| All names | Tylluan glustiog | Asio flammeus |
| All names | Tylluan gorniog | Asio otus |
| All names | Tylluan scops | Otus scops |
| All names | Tylluan wen | Tyto alba |
| All names | Tylluan yr eira | Bubo scandiacus |
| All names | Uchedydd | Alauda arvensis |
| All names | Wil-y-dwr | Cinclus cinclus |
| All names | Winc | Fringilla coelebs |
| All names | Ydfran | Corvus frugilegus |
| All names | Ysgraell | Sterna hirundo |
| All names | Ysgrech y coed | Garrulus glandarius |
| All names | Ysgrechen | Sterna hirundo |
| All names | Ysguthan | Columba palumbus |
| All names | Ysniten | Gallinago gallinago |
| All names | Yswidw las fach | Cyanistes caeruleus |
| All names | Yswidw llwyd fach | Poecile palustris |
| All names | Yswidw'r coed | Parus major |
