So why not make life a little easier for squirrels and birds during the winter? There are simple, uncomplicated ways of doing this. Hanging up bird feeders and erecting bird boxes helps the many birds which don't fly south to survive the winter easily.
However, opinions about bird boxes vary considerably. Winter is considered to be a part of natural selection. Weaker and sick creatures would normally die, so the intervention of humans may lead to an overpopulation of more prevalent species. Such species then have a competitive advantage over migratory birds and challenge their right to their habitat in the spring. However, the food supply for birds has reduced greatly in recent years since the use of pesticides has resulted in fewer insects for them to feed on. For this reason, moderate feeding is recommended in winter and can be considered to be a contribution towards maintaining the diversity of species.