I agree with coltandorf... and consider it a mating call to attract ladies to prime hunting grounds. Also agree with OP that haws are typically ambush predators.
It's never a problem until it is. Took more than 7 years before my first predator losses...

Early in the season before everything else is being born is hardest for my location, especially because I hatch it up. One broody Silkies hen lost 2 chicks in 2 consecutive days before I confiscated and put them under cover with other chicks. Then the hawk landed on top of their cover but got no more.
Just a few days ago, I was sitting about 5 yards from my bantam flock when I saw a bird dive between us, originally thinking it was a song bird diving my cat that was also nearby... there's NO mistaken a hawk tail when you've seen enough of them.

Despite my eyes following to the tree it landed in... I could not see it no matter how hard I tried it was well camouflaged. I kept watching anyways until it flew away ab out 10 minutes later.
I think it was last season this beauty was watching my flock, arriving and leaving about the same time each day. It was stressful for me but my flock has such short attention span they were clueless. Pic taken through a spotting scope with my cell phone.
I do consider temporary lock down that might save their life until the raptor gets bored and moves on as a highly effective means of flock preservation and NOT at all mean or inhumane because my flock isn't free range but is alive. Some folks have such high predator load that free range is literally a death sentence... just to keep it in perspective.
Also FWIW.. I did string fishing line across the top of my Silkie pasture and lost no more birds during that episode. Coincidence or effective, I can't say for sure but worth mentioning.
