Here, it is red-winged blackbirds -- especially in the Spring. Two of my regular training loops (84mi/105mi or 135km/169km) has a common portion that runs along a highway with tall bushes planted on each side. This is where the red-winged blackbirds nest. I can't get away from them, and the "Thwok-thwok" if them hammering my helmet is unpleasant, so I may try the zip-tie trick.
Thanks, John.
Best,
Dan.