Passer :: Passer (n.) One who passes; a passenger.
Passer-by :: Passer-by (n.) One who goes by; a passer.
Passeres :: Passeres (n. pl.) An order, or suborder, of birds, including more that half of all the known species. It embraces all singing birds (Oscines), together with many other small perching birds..
Passeriform :: Passeriform (a.) Like or belonging to the Passeres.
Passerine :: Passerine (a.) Of or pertaining to the Passeres.