behavior can evolve too, not just the organisms themselves
think of chikens. if chikens (okok, wildfowl) didnt hide their nests in the wild, things would come along and eat tasty chiken eggs. if a few chikens began to think it might be nice to find some secluded place to nest, they would also as a side effect, have their nests *hidden and be more * difficult for predators to spot. the ones who didnt hide their eggs wouldnt breed because all their eggs would be eaten. over generations, it became instinct to hide the eggs because ones who had that instinct were more likely to pass their genes on.