Air sacs of the lungs – serve as internal compartments which hold air and facilitate internal air passage to allow birds to have a continuous flow of large volumes of air through the lungs as a way to increase oxygen exchange capacity and efficiency.

Trachea – The primary function of the trachea is to transport air to and from the lungs. Without a trachea, a person would not be able to breathe. In addition to transporting air, the trachea helps defend against disease. The mucus in the trachea helps capture microorganisms such as viruses and harmful bacteria before they enter the lungs.

Bronchioles – The function of the bronchioles is to deliver air to a diffuse network of around 300 million alveoli in the lungs. As you inhale, oxygenated air is pulled into the bronchioles. Carbon dioxide collected by the alveoli is then expelled from the lungs as you exhale.

References:
Eldridge, L. (2020). The Anatomy of the Bronchioles. Retrieved from http://www.verywellhealth.com: https://www.verywellhealth.com/bronchioles-anatomy-function-and-diseases-2248931#:~:text=The%20function%20of%20the%20bronchioles,the%20lungs%20as%20you%20exhale.
F.L.POWELL. (2000). CHAPTER 10 – Respiration. Retrieved from http://www.sciencedirect.com: https://www.sciencedirect.com/science/article/pii/B9780127476056500110
Martinez, K. (2020). Trachea: Everything you need to know. Retrieved from http://www.medicalnewstoday.com: https://www.medicalnewstoday.com/articles/trachea#function