I see only one "some" statement present, the first statement, so I don't see a danger of combining two such here.
The first statement means that some things are simultaneously birds and mammals. All birds (so specifically these) have feathers, and all mammals (so specifically these) are warm-blooded. So those birds that are mammals are both feathered and warm-blooded, so some things are both feathered and warm-blooded, which is what the inference claims.
make some inferences using "none" and a "some" or "most" train. The Formal Logic info from which this drill is drawn discusses that when discussing the trains. For instance:
"No empiricists are libertarians"
"Some libertarians are atheists"
I get from this:
I can infer:
(some atheists are not empiricists)
So a "none" and "some" can lead to an inference.