Sentence:  The level below this is called the Phylum; <WSD>birds</WSD> belong to the Phylum Chordata, which includes all the vertebrate animals (the sub-phylum Vertebrata) and a few odds and ends. 
Meaning of the word marked with <WSD> tags:  A member of the class of animals Aves in the phylum Chordata, characterized by being warm-blooded, having feathers and wings usually capable of flight, and laying eggs.