Three large flocks

Three very VERY large flocks of geese or ducks flew over yesterday evening towards the East in North Yelm. Another small flock of about 10 were flying at a much lower altitude. A TWEET from Everette also mentioned seeing a flock of 60 SNOW GEESE headed towards the Snohomish Valley on Jan 19th. I've always thought that these large flocks are being driven by the weather, usually bad weather, and are headed towards a better location.  Most of the larger flocks that I have witnessed were flying or flew over at dusk.  I wonder why?

A few simple answers:

1) FAQ Birdwatchers Digest:
"...Still others, like geese and swans, make their migrations in family groups, led always by an older bird that has made the flight before. There is still much to learn, however, about how birds make such long flights and find precisely the right spot."


2) The Bird Lady
"..The Bird Lady:
Geese are among the few groups of birds that can migrate by day or by night."


3)BWB-ASF Library: Bird Migration Facts


4) PNNL: Science & Engineering - Shurb-Steppe Series: What About Canada Geese?


5)Geese Are Carb-Loading: Green Meditations Blog