Final answer:
Birds migrate for better access to food and breeding conditions or to avoid cold climates, and animals in hot, dry areas enter estivation, a state of torpor, to survive harsh conditions.
Step-by-step explanation:
Birds migrate mainly to find more abundant food sources and suitable breeding grounds or to escape from the extreme cold weather. Migration can be seen in many animal groups, such as birds, fish, mammals and insects. For instance, Arctic Terns travel annually between the southern hemisphere and their breeding spots in the Arctic to find ample food and a place to raise their offspring.
Estivation is the state similar to hibernation that occurs in hot and dry areas. During estivation, animals enter a dormant state called torpor, where their metabolic rate significantly decreases. This allows them to survive periods when their environment is less favorable, such as extreme heat and lack of water. For example, some species of amphibians, like the wood frog, possess an antifreeze-like substance in their cells to prevent damage during these harsh conditions.