Sometimes I think that scientists are so limited in their thinking.

The think that the ultimate reason the mother bird does this may be instinctual is one thing, but to reduce her action to only that is wrong.

I don�t believe the mother bird sees a fox approaching, and thinks, hmmmm, let me make sure my genetics survive in these chicklets. I believe she, like most mothers, simply figures out the best way to protect her babies. It has been demonstrated that birds show affection (not to say love since that annoys a lot of people - apparently humans are the only ones that are allowed to have that emotion) and it is that affection that will make the mother bird protect her babies.