- Ladder-tailed Nightjar
- Lapland Longspur
- Large-billed Tern
- Large-footed Finch
- Large Ground Finch
- Lark-like Brushrunner
- Laughing Falcon
- Laughing Gull
- Lava Gull
- Lava Heron
- Leach's Storm Petrel
- Least Bittern
- Least Flycatcher
- Least Sandpiper
- Lemon-rumped Tanager
- Lesser Black-backed Gull
- Lesser Black-backed Gull (graellsii)
- Lesser Greenlet
- Lesser Grey Shrike
- Lesser Horned Owl
- Lesser Kestrel
- Lesser Kiskadee
- Lesser Nighthawk
- Lesser Rhea
- Lesser Spotted Eagle
- Lesser Spotted Woodpecker
- Lesser Swallow-tailed Swift
- Lesser White-fronted Goose
- Lesser Whitethroat
- Lesser Yellowlegs
- Lesson's Motmot
- Light-crowned Spinetail
- Limpkin
- Line-fronted Canastero
- Lineated Foliage-gleaner
- Lineated Woodpecker
- Little Auk
- Little Bittern
- Little Blue Heron
- Little Bunting
- Little Bustard
- Little Crake
- Little Cuckoo
- Little Egret
- Little Grebe
- Little Ground Tyrant
- Little Gull
- Little Owl
- Little Ringed Plover
- Little Stint
- Little Tern
- Little Thornbird
- Little Tinamou
- Little Woodpecker
- Long-billed Dowitcher
- Long-billed Hermit
- Long-billed Starthroat
- Long-eared Owl
- Long-legged Buzzard
- Long-tailed Duck
- Long-tailed Ground Dove
- Long-tailed Jaeger
- Long-tailed Manakin
- Long-tailed Mockingbird
- Long-tailed Reed Finch
- Long-tailed Silky-flycatcher
- Long-tailed Sylph
- Long-tailed Tit
- Long-tailed Tyrant
- Long-wattled Umbrellabird
- Louisiana Waterthrush
- Lulu's Tody-Flycatcher
- Lyre-tailed Nightjar