Several times a week I find pools of brown/red liquid/blood on the tops of two metal trash cans that I store bird seed in near the feeders. Twice I found a small bone chip in the pools. I never find anything else to indicate what is being killed or who is doing the killing. I assume owl, because it is after dusk and the handles of the lids are clean (perch for something to let it's catch bleed out?). My trail camera never catches it, but has a five second delay. Any ideas?