From "fledglings or eggs," I would understand: the minimum of "fledglings" — two; the minimum of eggs — two. If there were only one fledgling or one egg, whence do I derive that he must still send away the mother bird? From "nest" — in any event.
"bird": Scripture speaks of a clean bird. — But perhaps it speaks of an unclean bird too? It is, therefore, written (Ibid. 14:11) "Every clean bird you may eat": This is a prototype, viz.: Wherever "bird" is mentioned in Scripture, a clean bird is understood (unless specified otherwise). … I might think to exclude (from the mitzvah) geese or hens that nested in an orchard; it is, therefore, written "before you," (and these are considered "before you").