Charlie - I've just finished reading a book by Hinesburg resident Bernd
Heinrich (I think the title's Winter World), in which he investigates your
question: why do other birds hang with chickadees in the winter? He was interested
first in how such tiny living things survive through northern winters, when they
lose so much of their body heat every night. His conclusion was that
chickadees make noise continuously while feeding, and other birds can stick with them
all day because of this noise - and this means a large group will still be
together when the sun goes down. The groups cluster together overnight in a
tight ball, sharing body heat and preventing heat loss. The poor unfortunate
creeper or nuthatch or left-over warbler caught alone at dusk will probably
not survive the night.
Sounds like you had a great time in the NEK!