CherryTree writes:

I have a nice cherry tree in my garden, it has very tasty cherries every
year but... not for long. Every year thousand of birds eat them all. I
erected a dud but this has no effect at all. Are there any reliable l
ways to protect the cherries? Thank you.

Other posters recommend netting.
Seems to me you'd end up with a lot of birds caught in the netting.

My mom used cheesecloth, a very loosely woven fabric.

We had good cherry pies that year.

--
Dan Espen