Cruel Nature?

 I used to have an office that looked out on a seldom used railroad spur.  In the winter the trees lining the spur was home to birds who would cluster together for I assume warmth.  Every morning quite a few of them lay dead on the ground under the trees. 

I don't know if someone cleaned them up or if they provided food to other animals.  I worked late enough to see them return for the night nosily as they jostled for a spot.  It clearly was a life-or-death matter although I read that the ones who died probably were malnourished.

I guess the ones who had trouble finding enough food had two problems.  They weren't strong enough to get a good spot where the warmth of the flock would help them and they couldn't withstand the cold being undernourished.

It seems cruel but the flock seemed to survive and when it became time to breed the weak had been weeded out.  Nature isn't cruel but it is pragmatic.  Your existence is not guaranteed, you have to fight for it. 

I never researched what type of birds these were but I'm pretty sure if I went to that office (it might not exist) the flock would still be flourishing.  

Nature made it stronger each year.