Some birds will abandon weaker chicks to focus on the ones most likely to survive. Others will allow siblicide. That these behaviors exist and have existed for billions of years is a fact orthogonal to morality because birds don’t have the capacity to reason about systems and the mortality of actions.
“Living things” is a sleight of hand, logically. When it comes down to it, everything is just atoms in the end. So why not murder? Why not steal? Why not exploit the poor? Reductionism leads us down some very dark paths indeed.