How to understand?

[Lyf]

Would you pls explain for me this sentence:
Kittiwakes defeacate over the edge of the nest, which keeps it clean, but this practice, as well as their tendency to leave the nest littered with eggshells, makes its location very conspicuous.

[Mister Micawber]

A kittiwake is a kind of seabird. They nest on rocky ledges. To keep the nest free of excrement, the birds do not use the nest for a toilet, but go to the bathroom over the edge of the nest. This leaves conspicuous discoloration around the nest. Pieces of eggshell are also left in the nest after the young hatch. The white eggshell and discoloration make the nest area quite visible and easy to locate for predators like larger gulls and mammals.
.