- Macaroni Penguin
- MacGillivray's Warbler
- Madagascar Cuckooshrike
- Madagascar Plover
- Magellanic Oystercatcher
- Magellanic Snipe
- Magellanic Tapaculo
- Magellanic Woodpecker
- Magenta-throated Woodstar
- Magnificent Bird-of-paradise
- Magnificent Frigatebird
- Magnolia Warbler
- Magpie Shrike
- Magpie Tanager
- Maguari Stork
- Malachite Kingfisher
- Malaysian Hawk-Cuckoo
- Malaysian Pied Fantail
- Malaysian Plover
- Mallard
- Mangrove Cuckoo
- Mangrove Rail
- Mangrove Swallow
- Mangrove Vireo
- Mangrove Warbler
- Mangrove Whistler
- Many-colored Chaco Finch
- Many-colored Rush Tyrant
- Many-striped Canastero
- Marail Guan
- Marbled Godwit
- Marbled Murrelet
- Marbled Wood Quail
- Maroon-backed Accentor
- Maroon-bellied Parakeet
- Maroon-tailed Parakeet
- Maroon Oriole
- Marsh Tit
- Marsh Wren
- Martinique Oriole
- Masked Booby
- Masked Crimson Tanager
- Masked Finfoot
- Masked Flowerpiercer
- Masked Gnatcatcher
- Masked Laughingthrush
- Masked Tanager
- Masked Tityra
- Masked Trogon
- Masked Water Tyrant
- Medium Ground Finch
- Melodious Blackbird
- Merlin
- Metallic-winged Sunbird
- Metallic Starling
- Mexican Cacique
- Mexican Chickadee
- Mexican Parrotlet
- Mexican Sheartail
- Mexican Violetear
- Mimic Honeyeater
- Mistletoe Tyrannulet
- Mitred Parakeet
- Moluccan Eclectus
- Mongolian Ground Jay
- Monk Parakeet
- Montane Foliage-gleaner
- Montezuma Oropendola
- Morelet's Seedeater
- Moreno's Ground Dove
- Mottle-backed Elaenia
- Mountain Blackeye
- Mountain Bluebird
- Mountain Bulbul
- Mountain Cacique
- Mountain Caracara
- Mountain Chickadee
- Mountain Elaenia
- Mountain Fulvetta
- Mountain Honeyeater
- Mountain Imperial Pigeon
- Mountain Leaf Warbler
- Mountain Parakeet
- Mountain Peltops
- Mountain Plover
- Mountain Shrike
- Mountain Thrush
- Mountain Wren
- Mourning Dove
- Mourning Sierra Finch
- Mourning Warbler
- Moustached Treeswift
- Moustached Turca
- Moustached Wren
- Muscovy Duck
- Myrtle Warbler