It's all relative. Cave temperatures stay fairly constant throughout the year. Missouri caves typically have an average yearly temperature of approximately 55-58 degrees Fahrenheit. We occasionally see birds in the entrance zone of the cave. The Eastern phoebe often builds nests here.
Vultures often raise their chicks here, too.
Birds do not normally enter a cave, they just use its mouth for protection from the weather. Snakes also use entrance areas. On hot summer days, the cooler air exiting the cave can help cool down a snake's body temperature. Snakes usually do not penetrate too far in, for there is little food deep in the cave. Woodland plants may live near the mouth of the cave.