Ahh. You've struck on the difference between English and American. Blackbirds ( the original Eurasian ones ) are
Turdus merula and very similar in habits to all the other members of
Turdus - which the American Robin is a member of ( the original Robin is a Flycatcher, but not one of your Flycatchers, one ofthe originals ). The Johnny-come-lately's

in the New World are a completely different family that includes Caciques, Oropendolas and what you call Orioles. It comes from the time when the people naming the birds weren't ornithologists so little stripey brown jobs became Sparrows, small stuff in forests and woodland became Warblers and black birds became ......... Blackbirds. Easy :t:
Chris