Yes it's quite common for some species to share roosts in the Winter months, I remember someone counting in double figures Wrens leaving an old nest, they build domed nests so must be very snug in there Robins stay with us all year round in fact we have 4 in our yard, trouble brewing when the breeding season comes around, seen a few minor skirmishes so far. We have a very old ewe, 17, She has trouble getting back on her feet after lying down so we keep her around the house and put her to bed inside at night, One of the Robins spends most of the day around her, comes in with her and shares her ewe nuts. This was one breeding with us a while ago