- Sabine's Gull
- Saffron-crowned Tanager
- Saffron Finch
- Sand-colored Nighthawk
- Sand Martin
- Sanderling
- Sandwich Tern
- Sapphire-spangled Emerald
- Sapphire-vented Puffleg
- Sardinian Warbler
- Savanna Hawk
- Savi's Warbler
- Sayaca Tanager
- Scale-crested Pygmy Tyrant
- Scaled Fruiteater
- Scaled Pigeon
- Scaly-breasted Hummingbird
- Scaly-throated Foliage-gleaner
- Scaly-throated Leaftosser
- Scarlet-backed Woodpecker
- Scarlet-bellied Mountain Tanager
- Scarlet-crowned Barbet
- Scarlet-rumped Cacique
- Scarlet-rumped Tanager
- Scarlet-rumped Tanager (costaricensis)
- Scarlet Macaw
- Scintillant Hummingbird
- Scissor-tailed Nightjar
- Sclater's Tyrannulet
- Screaming Piha
- Scrub Blackbird
- Sedge Warbler
- Semicollared Flycatcher
- Semicollared Puffbird
- Semipalmated Plover
- Semipalmated Sandpiper
- Sepia-capped Flycatcher
- Sharp-tailed Grass Tyrant
- Shining Honeycreeper
- Shining Sunbeam
- Short-eared Owl
- Short-tailed Antthrush
- Short-tailed Field Tyrant
- Short-tailed Hawk
- Short-tailed Pygmy Tyrant
- Short-tailed Woodstar
- Short-toed Snake Eagle
- Short-toed Treecreeper
- Siberian Jay
- Sickle-winged Guan
- Sierran Elaenia
- Silver-backed Tanager
- Silver-beaked Tanager
- Silver-throated Tanager
- Silvery Grebe
- Slate-colored Grosbeak
- Slate-throated Whitestart
- Slaty-backed Chat-Tyrant
- Slaty-capped Flycatcher
- Slaty-capped Shrike-Vireo
- Slaty-tailed Trogon
- Slaty Finch
- Slaty Flowerpiercer
- Slaty Gnateater
- Slaty Spinetail
- Slaty Tanager
- Slender-billed Gull
- Slender-footed Tyrannulet
- Small-billed Elaenia
- Smew
- Smoke-colored Pewee
- Smoky-brown Woodpecker
- Smooth-billed Ani
- Snow Bunting
- Snowcap
- Snowy Egret
- Snowy Owl
- Snowy Plover
- Sociable Lapwing
- Social Flycatcher
- Solitary Cacique
- Solitary Eagle
- Solitary Sandpiper
- Sombre Tit
- Song Thrush
- Sooty-capped Bush Tanager
- Sooty-capped Hermit
- Sooty-fronted Spinetail
- Sooty Shearwater
- Sooty Thrush
- South Polar Skua
- Southern Beardless Tyrannulet
- Southern Chestnut-tailed Antbird
- Southern Crested Caracara
- Southern Lapwing
- Southern Martin
- Southern Mealy Amazon
- Southern Mountain Cacique
- Southern Rough-winged Swallow
- Southern Screamer
- Spangle-cheeked Tanager
- Spanish Imperial Eagle
- Spanish Sparrow
- Sparkling Violetear
- Speckled Hummingbird
- Spectacled Whitestart
- Spix's Guan
- Spot-billed Ground Tyrant
- Spot-breasted Oriole
- Spot-breasted Wren
- Spot-crowned Woodcreeper
- Spot-throated Hummingbird
- Spot-winged Pigeon
- Spotless Starling
- Spotted Crake
- Spotted Flycatcher
- Spotted Nutcracker
- Spotted Redshank
- Spotted Sandpiper
- Spotted Woodcreeper
- Spur-winged Lapwing
- Squacco Heron
- Squirrel Cuckoo
- Steller's Eider
- Stock Dove
- Straight-billed Woodcreeper
- Streak-breasted Treehunter
- Streak-necked Flycatcher
- Streaked Flycatcher
- Streaked Saltator
- Streaked Tuftedcheek
- Streaked Xenops
- Striated Earthcreeper
- Striated Heron
- Stripe-chested Antwren
- Stripe-crowned Spinetail
- Stripe-headed Antpitta
- Stripe-tailed Hummingbird
- Stripe-throated Hermit
- Striped Cuckoo
- Strong-billed Woodcreeper
- Stub-tailed Spadebill
- Subalpine Warbler
- Sulphur-throated Finch
- Summer Tanager
- Sunbittern
- Sungrebe
- Surfbird
- Swainson's Thrush
- Swallow-tailed Cotinga
- Swallow-tailed Gull
- Swallow-tailed Kite
- Swallow-winged Puffbird
- Swallow Tanager
- Sword-billed Hummingbird