I think Fleecewife is probably right, but I did also wonder whether some of the sheep have been speaned. Does it look like all the lambs have a mummy? Are they mostly pairs of lambs? Otherwise, it could be a batch of speaned lambs with a few ewes to nanny them, and they’re crying for their mammies. Or a batch where the male lambs have been removed, and the mums and sisters are calling for the missing family member.
In all cases, the racket should stop after a day or two.