...I'm in agreement with mother nature is a personification of an abstract idea.
I quote the great Howard Bloom - "Mother nature isn't fluffy, she's a bloody bitch!" She's constantly throwing hurricanes, tornadoes, massive floods, and other hurdles for the human race to try to jump.
And in fact, I move to Darwin, as you so brilliantly reference.... "We do not see, or we forget, that the birds which are idly singing around us mostly live on insects or seeds, and are thus constantly destroying life."
So, as far as attributing the death to... bad parenting, SIDS, disease, weakness, chemicals (legal and non legal and unknown) being pumped into the body while the child is forming, suffocation, crazy mothers who snap due to postpartum depression, babies being born before they're suppose to come out (premie babies), crazy fathers who think that the babies stole the spot light from them, and sometimes good old clumsiness (oops! I dropped my baby!), shaking them to hard, touching their soft spot to hard, there are many things to attribute the death of hundreds of thousands of infants to. Attributing it to God is just lazy, and if he really did that, it's kind of mean. Not to mention the fact that plenty of people die each year, and that death is a natural process, oh and again (not to mention) the fact that plenty of baby animals die each year, and that fly you swatted earlier today might have just finished gestating long enough to fly out into the world before you, not God, killed it - but it was still young! (although not a baby, I think those would be larvae... but I'm sure plenty of those die to when some animal that thinks they're tasty eats them.)