I'm copying your haiku here so that I can talk about it without the cumbersome going back and forth between windows.
Spring dawn green valley -
Many years sentry of sheep,
songs of birds again.
Here I know this scene has had enormous power for millenia, watched over by sheep for centuries, but every year the birds sing again come spring. It's a lovely moment in eternal time. Very good!
Thanks @owasco. Appreciate the feedback. That's the intent of this haiku.