Which is a compound sentence?

 - At the auction, several paintings by famous artists were for sale, including one by Pablo Picasso.
 - Nile crocodiles mainly eat fish, but they will also eat zebras, birds, and other crocodiles.
The first sentence is the compound sentence. It is made up of two independent clauses joined by the coordinating conjunction but.
Nile crocodiles mainly eat fish, but they will also eat zebras, birds, and other crocodiles.