Spearow locations — where to catch

In Sinnoh (Diamond, Pearl & Platinum)

Route 225 — Walk
Sea Route 226 — Walk

In Johto & Kanto (HeartGold & SoulSilver)

Azalea Town — Headbutt
Celadon City — Headbutt
Johto Safari Zone — Walk
Route 10 — Walk
Route 11 — Headbutt
Route 16 — Headbutt
Route 22 — Walk
Route 3 — Walk
Route 33 — Headbutt, Walk
Route 35 — Gift
Route 4 — Walk
Route 42 — Headbutt, Walk
Route 44 — Headbutt
Route 45 — Headbutt
Route 46 — Headbutt, Walk
Route 47 — Walk
Route 7 — Headbutt, Walk
Route 9 — Walk
Vermilion City — Headbutt

In Kanto (FireRed & LeafGreen)

Route 10 — Walk
Route 11 — Walk
Route 16 — Walk
Route 17 — Walk
Route 18 — Walk
Route 22 — Walk
Route 23 — Walk
Route 3 — Walk
Route 4 — Walk
Route 9 — Walk

In Sevii Islands (FireRed & LeafGreen)

Canyon Entrance — Walk
Cape Brink — Walk
Kindle Road — Walk
Mt. Ember — Walk
Ruin Valley — Walk
Treasure Beach — Walk
Water Path — Walk

In Johto & Kanto (Gold, Silver & Crystal)

Azalea Town — Headbutt
Route 10 — Walk
Route 22 — Walk
Route 29 — Headbutt
Route 3 — Walk
Route 30 — Headbutt
Route 31 — Headbutt
Route 32 — Headbutt
Route 33 — Headbutt, Walk
Route 4 — Walk
Route 42 — Headbutt, Walk
Route 43 — Headbutt
Route 44 — Headbutt
Route 45 — Headbutt
Route 46 — Headbutt, Walk
Route 7 — Walk
Route 9 — Walk

In Kanto (Red, Blue & Yellow)

Route 10 — Walk
Route 11 — Walk
Route 16 — Walk
Route 17 — Walk
Route 18 — Walk
Route 22 — Walk
Route 23 — Walk
Route 3 — Walk
Route 4 — Walk
Route 9 — Walk

Other games (6)

Brilliant Diamond / Shining Pearl (Gen 8): Route 225, Sea Route 226
Let's Go, Pikachu! / Let's Go, Eevee! (Gen 7): Kanto Route 10, Kanto Route 22, Kanto Route 23, Kanto Route 3, Kanto Route 4, Kanto Route 9
Ultra Sun / Ultra Moon (Gen 7): Alola Route 2, Alola Route 3
Sun / Moon (Gen 7): Alola Route 2, Alola Route 3, Poke Pelago
X / Y (Gen 6): Friend Safari
XD (Gen 3): Phenac City

Spearow — full Pokédex entry