We lease our hay field to a local farmer.   The current agreement we have expires after this summer, and we would like to tweak the agreement a little bit to benefit the grassland birds we have here—mostly Eastern Meadowlarks and Bobolinks.   How long should a hay field be left undisturbed, to ensure fledglings are mature enough to get out of the way of the tractors and other equipment?  We live in upstate NY—a few hours south of Cornell University, actually.   We know farming is hard and don't want to make it any harder, but we are looking for a date range to work with, from a qualified source, to hopefully work something out that will benefit the birds and not be a huge hassle for the farmer.   Thanks for any help!