Whiffling
Descending rapidly from a height once the decision to land has been made, involving fast side-slipping first one way and then the other. The term is usually applied to geese (family Anatidae), whose flocks whiffle spectacularly, especially when wishing to avoid a long, slow descent over an area where wildfowling is practised.From Peter Weaver's Birdwatcher's Dictionary
Copyright © 1981 by Peter Weaver