when to let them fly for the spring

That's a good question. Perhaps you can do some local research on when the egg laying and rearing of young hawk chicks occurs. Hawks will target our birds more when there are hungry mouths to feed at home.

The hawks in our area are laying eggs around the 15th of March. Typically they will not hunt close to the nest and reserve that area for when the young come out of the nest. The hawk hits here have dropped in the last 4 days which tells me the nesting has begun.
Ken

Here in West Virginia,March is the worst month for hawk attacks...The hawks have YB`s and they are hunting all day to feed them...April is a little better,and usally May is pretty good...But the hawks are still hunting to feed themselves only,so you allways have to watch out for them...Alamo

I live in Michigan and my bird been locked up since last October. I plan on letting them out mid April.

I let my birds out earily morning and late evening. I have no choice , because old bird racing starts near the end of Apirl. I try to stay out in the yard and watch for the hawks, and try to scare them away. Hawks are a big problem for everyone.