Long-tailed duck

I am about birds again. Last week my friend and I saw a long-tailed duck on the Neva. As far as I understand it was an immature specimen. Why then it is migrating to the North?

Waterfowl

Though it is still cold a spring is coming and birds are arriving. There is an earliest open water patches on the Neva. As soon as the Neva opened a natatorial birds have been arriving. Last week (February, 24th) I saw a flock of he-mergansers. They stayed on the Neva more than three days.
Today I saw a red-wing among a fieldfares in Botanical Garden.