Do you have a good guard Dog? We had lost quite a few chickens and could never figure out what was killing them. We can't leave our Aussie outside at night because he will sit and bark at the door to come in. We ended up adopting a Black mout cur (Same Dog as Old Yeller) that had been horribly abused by her former owners. After a few weeks of teaching her that our livestock were not to be bothered she became a really good guard dog. She will even lay down in our goat barn and curl up with the goats. Withoput any training she has taken it upon herself to guard our property. She has killed a couple of coyotes, coons and one owl that were trying to get into our pens. Our neighbors bull dog decided to try to to get to the chickens one night and had to be put down the next day because of the injuries it got from our Cur Dog. She is even very very protective of my Wife and kids. I own many guns, but when it comes to marauding night time predators I would take a ticked off guard Dog anyday. Just my opinion. Since we got her we have not lost a single animal to attack.
I hope you get the animal that did this. I know how I felt when I found birds that had been killed.