Ah ok. When the hawk landed on their tractor, they all freaked out and clumped together in one corner. It's not a huge tractor so they don't really have anywhere to go. They were noticeably scared and seemed to want to get out of the tractor.
That's good. Does the tractor have anything they could realistically hide under? Their reaction tells me no, but I need to make sure. Try to observe as much as possible. My best helpers are doves. Young birds do not know what doves are, so they should hypothetically run for the trees. Doves are also pretty vocal, which again makes your life easier