Birds fly and migrate far higher and on a more regular basis than most people realise.
Certain birds, such as geese, have evolved to fly at high levels for just the same reasons as we do - efficiency.
I remember thermally in a glider years ago at 4,500 ft accompanied by swifts. Insects were obviously drawn by the thermal and the birds followed them. It seemed amazing at the time that such relatively small birds should be soaring and feeding at that altitude.
No surprises then for these bird strikes.
FOK
