yes, corvids are very intelligent

In fact, scientific studies (book at work sorry, can't quote for you) have shown that crows are the animals who can count the highest.
One test was by sending a bunch of people into a building, and sending a bunch out.
Most animals will have no problem once people have left, they see people leave, they assume all people have gone...
Crows however could count the people - so if 10 people went in, and only 9 came out, the crows would not be tricked into thinking the building was empty. Pretty cool, huh?

Unfortunately, ravens can not count quite so well as crows... close... but not quite...