I believe that the answer is A.
I only know about Blue Jays, so i hope this help you. Blue jays are sometimes known to eat eggs or nestlings, and it is this practice that has tarnished their reputation. In fact, they are largely vegetarian birds. Most of their diet is composed of acorns, nuts, and seeds—though they also eat small creatures such as caterpillars, grasshoppers, and beetles.
My guess would be temperature
Hope this helps :D
The respiratory system, as indicated in its name carries out the processes of respiration.
The processes of the transport of the respiratory gases are carried out by the circulatory system, a network of arteries, veins and capillaries, and NOT by the respiratory system (the lungs).