Animals in temperate zones that have seasonal fertility periods (goats, polar bears, deer) tend to have their babies in the spring when food is plentiful and the young have time to grow a little before needing to survive a winter. Estrus is triggered by day length.
I want to say that deer don't "calf" but I don't know what the right word is. I don't think they "fawn" even though sheep lamb, goats kid, and horses foal. I like it that dogs whelp, hogs farrow, and rabbits (I *love* this word:) kindle.