I've seen it in Portuguese, too, e. g. on the cover of a journal that Clarke
& Gauthier put (with many others) into a slide of their talk at the 1st
PhyloCode meeting to show how commonly the name Aves is used by
neontologists.
Googling for "uma ave" brings 199,000 results; of the first 10, however,
most are a poem or song text, and one is about a charadriiform and mentions
"Aves/pássaros (Birds)".
but it's used, IIRC, for your bigger, less songbirdy
types of birds.