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Comment by BSOhealth | Hacker News Reader

Just did, mind blown. I didn't know "parasitic brooding" was a thing in any animals, but totally makes sense.

As always, the HN collective helps my brainspace and experience of the world grow a bit.

Edit: I’ll pay it forward with another one: my favorite fact about bluejays is their evolved mimicry of hawks’ screams, to scare away other birds.

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Another fun bird fact about bluejays and crows: listening for a bunch of screaming crows and/or jays is a good way of finding owls, as they both seem to have an inherent hatred of owls, and harass them whenever given a chance. In my area, the poor owls rarely seem to get any rest from being swooped and yelled at all day.

I haven't seen this with owls but we've got some kind small predator bird like a peregrine falcon that the blue jays have it absolutely out for. The most interesting thing is once they start making the alerting calls, an inter-species mob will form with other birds of similar sized that aren't usually aggressive (like northern flickers) and they'll all harass the falcon until it flies off.

We have a big ponderosa pine on our property and sometimes the stellar jays go wild when there is a bird of prey up there.

We have seen barred owls, great horned owls, and cooper’s hawks.

https://imgur.com/a/ymDn7ff

In my area the yelling is always about hawks. The owls here are nocturnal so they don’t overlap.

It's called mobbing!

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