Snakes? Yeah, I can imagine . . .
Carol, my hens are out often during the Summer. It's always fun to watch them barreling out of the gate, take 3 steps and then it's, "My Gosh, this is grass!!"
They'd come to a full stop and eat. The hens would behave this way even if they'd been out twice before on the same day - only, they'd eat less grass after taking those 3 steps.
Chickens are not ruminants and cannot digest large quantities of fiber. So, they aren't likely to eat very much grass - especially when they can mix in some clover, lettuce, lambs quarters, chick weed, etc. Do they "need" it? Well, to my thinking they do need it but there seems to be a bit of uncertainty about how much pasturing or free ranging can contribute. The numbers I recall having seen were 10% to as high as 30% of their diet, maybe more. It also depends on how much you want them to produce with weight gain or eggs.
My intention has long been to give the hens all the commercial feed that they want to eat then to have greens of some sort available every day. This seems to make them happy
and that's important, too. Through much of the year, they are allowed out on the lawn to find green food for themselves. And, that makes them even more happy!
Steve