Buoyant birds
Stories from Physics
for 11-14
14-16
Diving birds tend to have plumage that traps less air in comparison to non-diving birds as the trapped gas exerts an additional buoyancy force. Hence, diving birds may have thicker feathers than other species to compensate for the poorer insulating properties of their plumage. As birds dive deeper, the trapped air becomes compressed, reducing its volume and also the upward force on the bird, increasing the power available at increased depths.
References
R. P. Wilson, K. Hustler, P. G. Ryan, A. E. Burger, & E. C. Noldeke, Diving birds in cold water: do Archimedes and Boyle determine energetic costs? The American Naturalist, vol. 140, no. 2, 1992, pp. 179-200, p. 192
