Any places where something was able to be breached. If you have weasels they can get through the tiniest places and are killers. I have netting completely covering all of my pens but a weasel would be able to get through. Luckily there aren't any where I live. I would still suggest putting up a...
Not knowing where you live and what predators may be lurking, it's hard to say. Put up a camera and see if anything is lurking. If a predator did kill your bird, it will be back. I had a fox kill some birds and never ate on them but I did catch it in the act of killing and I did eliminate it...