If another predator, that is more efficient hunter, enters the territory of the puffins, the puffins will find themselves in a very tough situation. They will either have to adapt very quickly, or die out.
The evolutionary pressure will be there fro the puffins to push them in a direction to adapt and be netter hunters, thus fight for their existence. That would mean that the puffin's beak, but also their speed and efficiency will have to improve in order to compete or even out-compete the new predator.
If the puffins do not manage to adapt relatively quickly, and a food shortage occurs, than they will die out, as they will lose the fight for food constantly.
