How do you get the legendary birds on Pokemon platinum?

Answer 1

you have to get the national pokedex and migrate them from fire red or leafgreen.(you need to catch them first and put them in your PC.)then go to that park place, and catch them.
. Items you need.

you need the marking map and natinaol dex. go to etrna city and then go to oaks house and they will be running around randomly just like cressellia adn mespirit