how do I single out two objects UID's of same sprite when they collide?

hello, I have been having issues with singling out UID's of two colliding objects which are both the same sprite (Bird). my intention is that the smaller bird gets destroyed and the bigger bird grows in size while many other birds do the same, but it keeps destroying other birds. how do I get the UID's of both birds when they collide? here is what I have so far.