The bird does not sometimes also eat ... Y.
= The bird does not eat Y at ... all.
= The bird always does not eat Y ... the case that [The bird does not sometimes eat Y ... .]
= The bird sometimes eat Y. (Bird ←s→ eat Y)
P1: Body weight = Energy animal needs to move ... br />
P2: Surface area - Energy animal has to move uphill ... surface area determines how much energy they **have** while ... don't have enough energy to do so. And ... he does not have enough energy to keep running uphill. ...
... />
> P1: Body weight = Energy animal needs to move uphill ... />
> P2: Surface area - Energy animal has to move uphill ... surface area determines how much energy they **have** while their ... out body weight: energy needed. Surface area:energy animal has to ...