When male redwings first return, it takes a while before they work out the boundaries of their territories, and those boundaries will move. As such, they have never seen nor heard a human. The crew has gone to great lengths to ensure that the birds do not have an opportunity to see people. This will greatly help them to remain as wild as possible yet still willing to follow the ultralight aircraft. Our last update said that high wires were extremely dangerous to migrating cranes.
Cranes have trouble seeing wires because there is nothing like wires in nature.
They have no idea how wide it's supposed to be, and since the ends of it are so far apart and far from them, they have no idea how far they are from it until they get dangerously close. Coils are three-dimensional, and give them a better concept of their distance from it, so they can more safely avoid smacking into the wire. The bird on the left, nearest the corn, is probably the male. That one appears slightly larger, and also seems to be on the watch. Male cranes are slightly larger than females, and more often take the responsibility to serve as lookouts.