Due to its system of air sacs connected to the lungs, the respiratory system of birds is arguably the most effective respiratory system of all air-breathers. upon inhalation, air first flows into posterior air sacs, then into the lungs, and then into anterior air sacs on the way to being exhaled. thus, there is one-way flow of air through the lungs, along thousands of tubules called parabronchi. which type of bird is most likely to benefit from air sacs, which reduce its weight? birds, such as geese, which migrate great distances birds that chip away wood, such as woodpeckers diving birds birds that rip apart prey, such as hawks and eagles