Neil Faulkner ( 25 Nov 2006)

From “Pressures produced when penguins pooh - calculations on avian defaecation” by Victor Benno Meyer-Rochow and Jozsef Gal. Published in Polar Biology (2003) 27: 56-28 (DOI 10.1007/s00300-003-0563-3)

Hygiene is essential to the success of any nest. Most parent birds make great efforts to keep the nest clean of faecal matter, the dead and the remains of food. Most of us have seen either on film or in person a parent tit or titmouse removing mucus encased faecal sacks from the nest. Many other brooding parents also need to keep their own waste from the nest. In many birds this is easily facilitated: move from the nest, only a few metres is needed, and defaecate. What when you are flightless, nesting on the ground and in a colony, live a frigid conditions and cannot leave the nest to relieve yourself? What if you are a penguin?

The strategy employed by Chinstrap and Adelie penguins is to climb to the top of the nest rim (constructed of pebbles etc.) turn so the vent* is facing outward, bow forward to elevate the vent and ‘fire’. A look at the nest site from above reveals a radiating pattern of white streaks of waste.

Penguin waste is of two types: 1) watery fluid, 2) a more viscous ‘olive oil’ like fluid. The pressures generated are calculated to be 10kPA (0.15psi) and 60kPA (8.7psi) respectively. These pressures are thought to be tuned to be sufficient to propel the waste sufficiently far without being wasteful of energy.

The writers above cite the reason for this manner of discharge as being personal, to maintain their plumage. This is very valid as the penguins feathers must be sleek for swimming, insulating for cold water and cold air temperatures and be attractive to mates. Additional reasons we see though include those in our introduction, the hygiene of the nest and the health of the young. There may also be a territorial function to the pattern, a visual expression of the territorial perimeter singing of passerines. It is possible that all these explanations are true. Behavioural biology often is far more complex than one paper can express.

* The ‘vent’, or cloaca, is the technical term for the aperture for the expulsion of faecal and urinary matter (often combined) and sexual organs. The combination of these structures saves weight for the bird.