A couple days ago I found a dead bird right next to the house (in what would be the flower bed, if we had flowers). It had died suddenly, as its wings were spread -- probably by a cat or something. I didn't examine very closely for cause of death. But what struck me was that at first I thought its head was gone; then I thought its head had been somehow driven into the ground. On closer examination, I realised that its head was covered with these little straw-like needles lying on the ground. (I'm not sure what those straw-like needle things were, but maybe they were dead cedar needles fallen from trees.)
Ants were already eating it and as always, I wanted to make sure the poor bird was definitely dead and not being finished off painfully by the ants, so I flipped it over. The ants scattered and I saw the bird was truly dead. However, when I returned later that day the head was again covered in the needles, and this time I was able to see the ants actually engaged in the painstaking task. I figured they were burying the whole body for some reason, but they only buried the head.
By the next day something else had come along and finished off the bird. But I was wondering why ants bury the head.