Are there no people in the land?!
Radak: The people who used to be in the land, i.e. Yisrael, are not.
Why did the birds depart?
Radak: This is an exaggeration. Amidst the great desolation of the land, birds were eradicated from there, and do not fly through the land.
Why do the verses discuss Churban of the land, people, birds, and vegetation, in this order?
Malbim (24): After discussing Churban of the land, it discusses Churban of those on the land. It begins with the purpose of creation (man); the rest is to serve him. It goes in reverse order of creation, from man on day six to vegetation on day three.
Why does the verse discuss Churban of birds, but not of animals?
Malbim: The level of beings below man are Ba'alei Chayim. Of them, birds are most distant from man; they were created on the fifth day.
