It looks like Chinstrap and Adélie penguins need to generate considerable amounts of pressure to be able to propel their feces outside of their nests, while remaining inside of the nests (brilliant evolutionary achievement?), so a paper titled Pressures produced when penguins pooh - calculations on avian defaecation (V.B. Meyer-Rochow, J. Gal; 2003) was produced.
The authors utilized straightforward problem simplification — distance, height, density, viscosity — and decided to tackle this problem face-first, because, as they say
"Anyone (...) must have wondered about the pressure the bird generates."
They neglected the effect of wind (and air friction, presumably). They also performed some experimental measurements (albeit from a distance), while participating in the first Jamaican Expedition to Antarctica.
The authors discuss the dynamic viscosity of the expelled material, its color, consistency, and amount, and provide us with a wonderful scientific model (drawing) of a pooping penguin, which I can thoroughly recommend. They concluded that the viscosity of penguin poo resembles that of olive oil, and that they generate pressures of up to 60 kPa while pooping on land. Fascinating. After the initial utilization of the highest pressure, the pressure rapidly drops, which creates streaks of poop instead of blobs. That sounds reminiscent of all birds — would anyone want to take me up on examining the poop pressure of pigeons?