Why birds and mammals are more active in the middle of winter than amphibians reptiles?

This statement is not correct. In general, birds and mammals are less active in the middle of winter compared to amphibians and reptiles. Birds and mammals are endotherms, meaning they generate their own body heat, while amphibians and reptiles are ectotherms, meaning they rely on external sources of heat to regulate their body temperature.

In the middle of winter, the environment can be very cold, which makes it difficult for ectotherms to maintain a high enough body temperature to be active. As a result, many amphibians and reptiles go into a state of brumation, which is similar to hibernation. During brumation, amphibians and reptiles become inactive and their body temperature drops significantly. This allows them to conserve energy and survive the cold winter months.

On the other hand, birds and mammals are able to maintain a high body temperature even in cold weather because they generate their own heat. This allows them to stay active throughout the winter months, although some birds and mammals may reduce their activity levels or migrate to warmer climates to escape the harsh winter conditions.

So, in general, it is not true that birds and mammals are more active in the middle of winter than amphibians and reptiles. In fact, the opposite is usually the case.