From Bulbapedia, the community-driven Pokémon encyclopedia.

Birth Island
Location:	South of Fortune Island, east of Quest Island
Region:	Sevii Islands
Generations:	III
Pokémon World Locations

Birth Island is a location near Fortune and Quest Islands, in the Sevii Islands. It can only be accessed after downloading the Auroraticket through Mystery Gift, talking to the sailor in front of the Seagallop Ferries' dock, and selecting it as the destination. Like Navel Rock, it is not visible on the Town Map by default.

Emerald

Though not part of Hoenn, Birth Island is visitable in Pokémon Emerald. The Auroraticket can be obtained in the same way, with the exception of being intended for the S.S. Tidal.

Pokémon

Name	Games			Location	Levels	Rate
All Times
Deoxys (Attack variation)	FR			Event	30	Only one
Deoxys (Defense variation)		LG		Event	30	Only one
Deoxys (Speed variation)			E	Event	30	Only one

The Sevii Islands
Islands:	Knot | Boon | Kin | Floe | Chrono | Fortune | Quest | Navel | Birth
Towns:	One Island | Two Island | Three Island | Four Island | Five Island | Six Island | Seven Island
Routes:	Treasure Beach | Kindle Road | Cape Brink | Bond Bridge | Three Isle Port | Three Isle Path
	Resort Gorgeous | Water Labyrinth | Five Isle Meadow | Memorial Pillar | Outcast Island | Green Path
	Water Path | Ruin Valley | Trainer Tower | Canyon Entrance | Sevault Canyon | Tanoby Ruins
Landmarks:	Mt. Ember | Berry Forest | Icefall Cave | Rocket Warehouse | Lost Cave
	Altering Cave | Pattern Bush | Dotted Hole | Tanoby Key | Tanoby Chambers

Game locations of Legendary Pokémon
Articuno	Zapdos	Moltres	Mewtwo	Mew	Celebi	Jirachi
Seafoam Islands	Power Plant	Victory Road*	Cerulean Cave	Faraway Island*	Ilex Forest*	None*
		Mt. Ember*
Raikou	Entei	Suicune	Lugia	Ho-Oh	Latias	Latios
roaming Johto*		roaming Johto*	Whirl Islands*	Tin Tower*	roaming Hoenn*
		Tin Tower*
roaming Kanto*			Navel Rock**		Southern Island**
Regirock	Regice	Registeel	Kyogre	Groudon	Rayquaza	Deoxys
Desert Ruins	Island Cave	Ancient Tomb	Cave of Origin*		Sky Pillar	Birth Island*
			Marine Cave*	Terra Cave*
Uxie	Mesprit	Azelf	Dialga	Palkia	Heatran	Regigigas
Lake Acuity	Lake Verity* roaming Sinnoh	Lake Valor	Spear Pillar		Stark Mountain	Snowpoint Temple*
Giratina	Cresselia	Phione	Manaphy	Darkrai	Shaymin	Arceus
Turnback Cave	Fullmoon Island* roaming Sinnoh	breed Manaphy	Egg*	Newmoon Island*	Flower Paradise*	Hall of Origin*