Galarian Birds
The Galarian form of the three legendary birds can spawn near the Dyna Tree. There is currently no way to force them to spawn, just like the legendary beasts you must wait for them to spawn near their structures. Poke snacks will help a great deal here.
Locate Structure Command
/locate structure cobbleverse:dyna_treeHow to Obtain
Materials Checklist
Craft the Dyna Tree Radar to locate the Crown Spire. You will need to find Max Mushrooms in lush caves first in order to craft the Dynamax candy for this radar.

After putting the radar with an empty map in a regional cartography table, you can follow the resulting map to the Dyna Tree. This is what the Dyna Tree looks like.

Moltres spawns around the tree during daylight (6am - 6:30pm). Poke snacks are recommended to increase spawn chance.
Articuno spawns around the tree during evening (6:30pm - 5:30am). Poke snacks are recommended to increase spawn chance.
Zapdos spawns around the tree during thunderstorms. Poke snacks are recommended to increase spawn chance, especially since thunderstorms can't be forced.