Be careful the next time you quietly curse a magpie attacking you during breeding season. It may know what you are thinking. Why is it that the birds seem to know the personalities of individuals walking by? If you have fed them in the past they appear to remember you and let you go on by unhindered while swooping down onto the heads of other people.
Crows have been observed hiding food from other crows. This is not due to stress as was once believed. There is still contention between the two opposing groups of scientists. Tests on scrub jays it was claimed proved that they were hiding food from more dominant Jays. This was really a hypothesis, not real proof.
The other group claims that birds are conscious of others and what other may be seeing, like humans. In their tests bird were allowed to hide peanuts in a litter of corn cobs. If another bird was watching they later came back and re-hid the peanuts. When they buried peanuts on their own they rarely re-hid them.
This was the key finding - stress from stealing hidden peanuts should change behavior. It didn't! Birds were given a tray of ground cobs but an empty bowl with no peanuts. They were then given cobs and peanuts which they hid. Researchers stole all the peanuts from this tray.
The birds were split into two teams for study. One had peanuts, a new cob tray with the "sham" empty tray. The other had peanuts, a new cob tray with the "pilfered" tray. Stress from knowing that peanuts had been stolen earlier did not change behavior. Both teams of jays hid peanuts in the same way.
The "contra" group of scientists claimed that the sham tray with no peanuts stressed the birds just as much as the pilfered tray. Obviously, the scientific test for testing new scientific claims is not set on concrete. It can be bent for one's own purpose.