As nouns the difference between passerine and treepie

is that passerine is any bird of the order passeriformes, which comprises more than half of all bird species while treepie is four closely related genera (dendrocitta'', ''crypsirina'', ''temnurus'' and as of recently also ''platysmurus ) of arboreal long-tailed passerine birds in the family corvidae.

As an adjective passerine

is of, or relating to a passerine or perching bird.