Nest, Habitat
noun
The kanji and the word are exactly the same. That means they share meanings as well. This can refer to all kinds of things, like a spider's web or a mouse's burrow or a bee's hive, etc. Basically, it's a place where animals live, not necessarily just a nest as in a bird's "nest," etc.
す
The reading is the same as the one you learned with the kanji.
巣の中では、ツバメの雛が五羽、ぴいぴい鳴いていました。
There were five baby swallows chirping in the nest.