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...
Sorry, my question wasn't clear. I was more so asking if you've ever seen them quickly take cover/run towards any potential hiding place at the sound/sight of what they presume as danger. A good test for that would also be their reaction to the hawk, even though they were in their coop. At this...
You say there is a lot of tree cover. Have you ever seen them retreating into it? Has any bird taken the role of lookout? Free ranging always has its risks. It's up to you to decide what level of risk you're comfortable with