Why do thrush birds tend to have closed feathers in hot summer, but loose feathers in cold weather?

The thrush's feathers, like those of other birds, can not only prevent rain, wind, dust and sand, but also help to fly and keep warm, and can also regulate body temperature.

Because thrush has no sweat glands, it always opens its mouth in hot weather, making it more difficult to breathe. At the same time, the feathers are tightly closed, which can reduce the gap between feathers and make the heat in the body easily discharged. In cold weather, fluffy feathers increase the gap between feathers, just like soft cotton wool, which plays a role in heat preservation.

However, whether it is too hot or too cold, it is not good for thrush. Measures should be taken to keep birds at normal temperature.