Canada Goose - Weird in-flight behaviour

[Dinusaur]

This week on Monday while I was at Reesor pond I saw flocks of Canada Goose flying into the pond from north. From time to time I noticed that in a flock, some birds were breaking away from the flying pattern by diving down sideways or flying upside down as if to avoid some unseen barrier. I thought this little jiggy was to avoid flying insects that were coming onto their path. I saw this strange behaviour in quite a few groups. While flying upside down they kept their heads right side up. Here are three of the photos I took that show this strange flying behaviour. Google says that this apparent random behaviour is called 'whiffling' and the geese do that to lower their speed before landing. Who knew. Nature is amazing.

[Rotarran]

Ducks do that as well.  It does seem like a quick & dirty way to lose altitude.  Nice captures by the way, especially of the one upside down...awesome shot!