Will this come back and does anyone know about what time it usually does occur?

this totally comes back. It doesn't come back exactly at Spring (Autumn) because many other site-things must happen exactly at that date.

It also doesn't usually start a few days after because the Atebus Revolution Masquerade is typically just about to start and staff is busy preparing for the special event. Over the top of this and have hinted something special that they are working on is coming up soonish. The delay for this kinda thing from first hints is about six months so IMO it will be happening sometime between the end of the ball and Vesnali.

Expect a delay on this.

I was thinking it would probably be a Springish(I live in Florida and sometimes just completely forget about Spring because it usually just all feels like summer,lol) time event but was not sure, thank you :) I am ready to do those achievements.

I do hang out here and I have found that in subsequent years new users do have enough time to get all the birds in one year

I hope so, thank you again :)

you are welcome