I'm so glad you said that. I'm trying to get confident about distinguishing raven from crow. Everyone says "Oh but it's easy, the raven is much larger" - but if you see a single black bird at an indeterminate distance in relatively featureless countryside you don't know well, how do you know whether it's a big bird far off or a smaller bird nearer to?

OK, a raven has a wedge-shaped tail - but you can't always see that, and it's beak is "heavier" - but again without direct comparison that's difficult.