[rococode]

What I've read is that crows are smart for the same reason that dolphins are smart ("social intelligence"). Crows also tend to live in flocks/groups, unlike many other bird species.

Not a great source, but here's an excerpt explaining that they tend to grow up in groups:

But growing up is a different story. During younger years, they often live in larger flocks dubbed juvenile gangs. "It's exactly how it sounds: they're basically a bunch of teenagers trying to compete with each other," Brown says. And it's these relationships they have to keep tabs on.

https://cosmosmagazine.com/social-sciences/why-are-crows-so-...

[PeterisP]

The octopus is a counterpoint to this, being very intelligent but absolutely solitary.

[mcv]

But it has excellent hands.

Humans may be unique in having both complex social structure as well has hands.

[nicoburns]

Arguably elephants fall somewhat into this category...

[mcv]

I've often wondered whether elephant-like aliens would make sense, exactly because of this.

I guess Niven and Pournelle had the same idea for Footfall.