Partnered Animal Common Cycle

So I was thinking about how to represent Overgrowth's abundance in common, small animals that don't use the mutate mechanic. The world's overgrowth is represented not just with creatures growing out of size, but also with fecundity,

I thought about the idea of bringing in the populate mechanic, but I'm already bringing in detain. So I though about a very simple common space where you play a creature, and its partner shows up on your next turn.

I'm not really sure about the mana costs and size on these guys, but I know I want them all to be common and played early.

The idea of partnered snakes seems a little weird (I initially had them as cats), but I'm warming to the idea of a black/green vermin theme and I want both these creatures to fit in. There is also going to be a white/blue bird lord, though I'm still figuring out ideas of how I want him/her to play.