chickens, domestic fowl
雞 centers on domesticated fowl, specifically chickens. It refers to the bird as a household animal rather than wild birds.
雞 combines 奚 (which likely contributes the sound) with 隹 (bird), forming a character for a specific kind of bird, the chicken.
The left side 奚 looks like a hand over a tied-up creature, and the right side 隹 is a bird. Picture a hand holding a domestic fowl: a chicken.
For ケイ, imagine a chicken pecking at a cake: cake -> ケイ, and the chicken eats the cake.