Another interesting article from the Cool Green Science site, this one
about robins.  Only the first section addresses robins in winter, but the
rest is about their migratory behavior (many but not all do the
North/South
route), and other behaviors.

https://blog.nature.org/science/2018/02/07/why-are-you-seeing-robins-in-winter/

I've occasionally seen mobs of robins hanging out together in the woods in
very early spring, still winter by our reckoning and that of the birds.

Jane
(Shoreham)