Leyla H. answered 18d
Professional Spanish Interpreter AND Flute Performer ... for 20+ yrs!
The two previous responses demonstrate how geography affects language. As Igor explains, a "pajaro" is a type of "ave." Nomariely explains that, colloquially, Puerto Ricans say "pajaro" for all "aves."
I learned that "ave" translates to "bird" in English, while "pajaro" translates to "parrot" (or tropical birds). In Puerto Rico, a tropical island, all of the birds would be tropical birds, explaining the universal usage of "pajaro" to mean "ave."
Igor also mentions the difference between flighted birds ("pajaros") and flightless birds ("emus"). If you're interested in an additional thought experiment, how do "pollos" fit in to this conversation?
I hope this helps.