At Madder Cliffs in the Antarctic Sound, there is a large mixed colony of Gentoo and Adelie Penguins. The Gentoos are breeding close to the shores, the Adelies higher up on the mountain. For me, this was a new location, so I can’t say anything about how the two species are doing (like with the mixed colony on Petermann Island). A subtle difference in breeding biology between the two species was visible, however.
As Adelie Penguins are used to breed further south and in more harsh climates as Gentoos, they start earlier in the season as the Gentoos. At the end of December, when we visited this colony, most Adelie Penguins had reasonably large chicks, where the Gentoo Penguins still had eggs or tiny chicks. This difference allows the Adelies to breed as far south as 77ºS and make the best of the rich Antarctic summer.