I have never had this problem before, I let my chickens out to free range with the warmer weather this week. I have three one year old hens a rooster about six months old, and nine 8-9 week old pullets. All the older birds went back to roost at dark, but I had to hunt down the nine young birds, they where huttled together in the middle of the yard! I tried two evenings, I only let them out an hour or so before sunset, and both times I have to chance down the younger birds. How old do these birds have to be before they learn to go back to the roost? And they are not yet "roosting", they stay on the coop floor all the time. The older and younger birds are not related. The younger are from a hatchery, the older are "farm raised".