To get Taillow in HeartGold, you must have obtained the National Pokedex. Then, go to Cherrygrove city with a Pokemon that knows Headbutt, then Surf at the beach. Get off at the small island farthest north, use Rock Climb, then, at the top of the hill, use Headbutt on one of the four trees surrounding you. It will appear in the trees after a couple of tries. Taillow evolves into Swellow at Level 22.
Taillow evolves at level 22.
You can't catch a Taillow in Pokemon Platinum, but you could catch the later evolution (Swellow) using Poke Radar on Route 213, and then breed it to get a Taillow.
The Pokemon taillow is a Flying Type
swellow
Taillow is #276 in the national pokedex, and it is a Normal-Flying type Pokemon.
Taillow isn't in Leaf Green, just emerald Sapphire and ruby
i think at level 32
level 22
22
breed a swellow and ditto
it was taillow