Dippers are ever present in our area unless the rivers are in spate; certainly the cold does not put them off. When you think about it, flowing water is always above zero centigrade even when the air temperature is below.
They get ready to breed early in the year, establishig pair, although they often wait until they feel conditions are right before lining the nest and laying a clutch. I have found this indididual to be unusually approachable so we have been "enjoying" once another's presence. You can see that I have caught it in mid poop. Of course we are always looking out for Dipper poop on the rocks in streams to confirm that the birds are in residence.