Thread by @corvidresearch

I’ve been getting a lot of questions lately on the theme of “did I really just see crows killing another crow?!” so let me dedicate a quick thread to the topic.

Let’s cut to the chase right away: yes, crows sometimes kill each other. Look, crows are complicated. Yes they engage in behaviors that we find enducing of “awwws” like gently preening their mate, or bringing people “presents”, or playing silly games.

But at the end of they day they’re also competitive & need to survive & will kill to do it.

There’s 2 main reasons crows kill each other. The first is territory transgressions i.e. someone crossed a boundary they shouldn’t have and got attacked by the pair (and whoever they recruited).

This is especially relevant at this time of year, when males will try and sneak on other territories to copulate with the female. So these kinds of lethal interactions seem to tick up right now.

The second is that, for reasons not entirely clear to us, crows will go after and kill already injured crows. This scenario is usually the hardest for people to swallow because it feels so entirely unfair. But sometimes, it’s what they do. Even with juveniles.

Maybe they do that because they’re willing to take advantage of any opportunity to reduce competition, or maybe as a way to reduce predation of crows. We don’t really know.

So yeah, it’s a grisly part of their behavior. But it’s also, on the whole, rare. And before any crow haters are tempted to weaponize this into a reason “crows are the worst” let’s put this into broader context.

The reality is that tons of other animals also, sometimes or even regularly, kill members of their own species for a variety of reasons.

Many social primates with form coalitions and kill rival groups to reduce competition, or will kill more dominate individuals even from within their own groups. scholar.google.com/scholar?hl=en&…

And a quick google search reveals a whole grab bag of misc. observations of different kinds of animals killing their own, from pumas to wolves, to ground squirrels and tree swallows.

Things gets really dramatic when you look specifically at infanticide, something crows also do, albeit it seemingly extra rarely.

For example cliff swallows may destroy their neighbor’s eggs so that they can drop their own eggs off. sora.unm.edu/sites/default/…

And of course some mammals like brown bears, lions, most primates, many dolphins etc. will commit infanticide in order to mate with the female(s).

And I’ll never forget, during my stint on a caspian tern colony, watching curious babies take a mere couple steps too far from their nest only to be bombarded with pecks from their angry adult neighbors, resulting in a confused panic which led them further astray & usually dead

In conclusion: yes crows sometimes kill each other for reasons that are complex and not always clear, especially at this time of year, and not unlike many other animals.