I've seen the small flock of White-crowned Sparrows on their way south, stopping by the yard for a few days. I'm sure they're the same group that were here in the spring. What an amazing thing. I remember some 40 years ago in Bigfork Montana where I lived at the time, an older woman who fed birds and insisted that she recognized each individual and had names for them all. I raised an eyebrow at this, but as I approach that age of being an "older" woman who feeds birds, I think, perhaps, she probably did know each of those individual birds and they, in turn, knew her.