Certified Wildlife Rehabilitator Practice Test

How does avian respiration differ from mammalian respiration?

1. Birds have a more complex lung structure

2. Birds have a diaphragm

3. Birds have no diaphragm

4. Birds can hold their breath longer

The correct answer is: Birds have no diaphragm

In birds, the absence of a diaphragm is a key feature that distinguishes their respiratory system from that of mammals. Instead of a diaphragm, birds have a unique lung structure that allows them to maintain a continuous flow of air through their lungs, enhancing their oxygen exchange efficiency. Birds utilize a system of air sacs that work in conjunction with their lungs. As birds inhale, air flows through the trachea and fills the posterior air sacs. When they exhale, the air moves from the posterior air sacs into the lungs, where gas exchange occurs. On the subsequent inhalation, the air from the lungs moves into the anterior air sacs and is expelled on the next exhalation. This mechanism ensures that air is always flowing in one direction through the lungs, providing a constant supply of fresh air and facilitating a more efficient respiratory process, which is particularly advantageous for the high-energy demands of flight. Comparatively, mammals rely on a diaphragm to create negative pressure in the chest cavity, drawing air into the lungs. The fact that birds lack this diaphragm is significant, as it reflects their evolutionary adaptation to flight, allowing them to optimize their respiratory efficiency in a different manner.