The respiratory system of birds is vulnerable to impurities in the air, which can cause a bird to choke.
The impurities in the air can cause a bird to choke. The respiratory system of birds is vulnerable at the impurities in the air.
The respiratory system of birds is vulnerable at the impurities in the air. The impurities in the air can cause a bird to choke.
The respiratory system of birds is vulnerable at the impurities in the air. The impurities in the air can cause a bird to choke.