Crows are super opportunistic. If they see a chance for an easy meal they'll go for it. They may just be curious about the new things in the neighbourhood, rather than actively looking at your chicks as food. But that doesn't mean they won't think "hmm, that looks like it might a quick dinner".
However, crows are not birds of prey.
They're not very good hunters, and not good at carrying large carcasses in their claws, just their beaks. They take tiny chicks and fledglings because they're easy to grab. So while it's not outside the realms of possibility that they'd kill a smallish chicken, it's not hugely likely.
Still, always better safe than sorry, keep them secured when you can't be around until they're big enough that a crow will look at it as too much effort.
However, crows are not birds of prey.
They're not very good hunters, and not good at carrying large carcasses in their claws, just their beaks. They take tiny chicks and fledglings because they're easy to grab. So while it's not outside the realms of possibility that they'd kill a smallish chicken, it's not hugely likely.
Still, always better safe than sorry, keep them secured when you can't be around until they're big enough that a crow will look at it as too much effort.