How to keep warm in winter

The sparrows will become fluffy in winter, so that they can have a warm effect.There are 27 types of birds, and the size and body color are very close. Five of which are distributed in the territory of our country. They are usually inhabited in a place with an altitude of 300-2500 meters.Their traces, and they live in cities, towns, villages where humans gather, and have a bold personality and strong curiosity.