Jays can be seen in many areas of the states and Canada. They have been witnessed sitting on an ant nest to deliberately annoy the little characters. This in turn leads the ants to retaliate by soaking the bird with formic acid. The bird knows this acid is a natural pesticide which kill the parasites on the Jay.
Green-backed Herons are known for their patience and apparently it has payed off. They observe fish coming up to catch insects on the water. But they also noticed it is the ripples or movement that attract the fish. With this knowledge, they gather all kinds of contributions like: seeds, flowers, feathers and dead insects. Dropping these on the water causes an initial bit of movement that draws the fish up to the waiting Heron.
Ravens are very competitive and smart. A look-out is usually posted nearby and gives the alert to others that a food source is near. But the initial bird to find the source often leads the group off on a wild goose chase. Then he sneaks back to enjoy the meal himself. I have seen something like this when the peanuts I throw out are taken by the lead bird who hides them in my grass so that when the others arrive, he has a private stash.
Sometimes a bird doesn’t have to be terribly clever. Instead, he can have excellent vision like the buzzards who can spot a mouse moving from the height of 15,000 feet. They have 20/05 vision which means what we see clearly at 10 feet, they see at 40 feet.
An interesting fact that helps birds is the way they use their eyes. They see objects with one eye at a time. The left eye picks up color and the right observes motion. From years of owning doves, I can also tell you that they use their eyes and head to pinpoint where they will land. They bob their heads up and down an also from side to side creating imaginary cross hairs. The idea is to land dead center, like a navigator does when dropping something from a plane.
Cardinals are beautiful looking birds who have been observed treating goldfish like their own baby birds. The fish open their mouths which no doubt triggers maternal instincts to the bird and it tries to keep them fed with worms for a couple of months. You could argue that this makes the bird seem rather stupid. But I believe it makes the bird happy to supply this need and this suggests an intelligence beyond mere instinct.