alt Hacker NewsOne of the craziest behaviors I have seen was from a murder of American crows in a big city area sidewalk I walk down frequently - occasionally, I have observed homeless and vagrants throwing stuff at them, because sometimes they sleep under the powerlines where the crows like to perch and I think the crows defecate on them or something.
It's well known they can carry grudges, but one day, as I was walking down the sidewalk, a pretty sizable rock smacked the pavement next to me, seemingly out of nowhere. If it had hit my head I would have been hurt. I finally look up and see a big crow staring directly down at me - it had dropped it from the power lines, it had seemingly been intentional, maybe as a warning, I don't know. I attributed it to malice towards the vagrants that harass them.
I was amazed at how much intelligence it would take to 1) form a grudge 2) form intent to threaten/harm, 3) formulate a plan using a weapon with cause -> effect to execute intent, 4) wait for opportunity.
I have observed a lot of very intelligent behaviors from these birds but that was the wildest one. I have seen it happen once since, so I'm convinced it isn't an accident.
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I remember reading an article in National Geographic of how crow's brains are much more interconnected than is the norm in mammals, i.e. IIRC they have a higher density of synapses between neurons. From that article, it seems that the usual brain weight vs. body weight to determine intelligence, which seems can be used to approximate intelligence in different species of mammals, cannot be used for birds (or at least crows, which the article was focusing on).
In other words, they seem to achieve better results with smaller brains than we thought. And yes, crows (in EU) do exhibit some pretty intelligent behavior.
They're even apparently able to pass their grudges along to other crows who did not have first-hand experience with the subject of the grudge.
My understanding is crows can recognize individuals, so I would think back to what you did to piss off that crow, or that crow's friends.
Crows in country will wait for a newborn deer to be left alone in a field by their mothers shortly after birth to peck the baby's eyes out so it dies and the crow can eat it later. My neighbor had told me about this happening, and maybe a month later I saw a fawn with its eyes pecked out shortly after it had died. The doe just sat at the edge of the field by it all night. So sad, but really smart of the crows.
Crows have also been known to alert predators like wolves to easy prey so they can pick the remains.