It struck again last night!

[PirateGirl]

My first thought when I read your post was bobcat. You said it killed many. A bobcat can kill many and will keep coming back to collect the bodies until it removes them all. A bobcat can climb, which you mentioned, and fit though a much smaller opening than you'd expect. The print you posted a picture of looks like a can print. The gap above the door you posted a picture of is big enough for a cat to get in. Regardless of what it is, you now have to try and catch it in the act, as in trap it or lie in wait near the coop and hope your scent doesn't deter it. Cats (and weasels) are both quite clever, good climbers, good killers, and will return, however they both can know enough to avoid traps and avoid people. This is no easy task.

As others have mentioned, before your remaining birds go back in the coop, you may have some fortifications to do. One area of opportunity I saw is along your roof line. You appear to have corrugated roofing, and the gaps this creates are large enough for many small rodents/weasels/snakes/etc. If you are counting on these gaps for ventilation, you can cover them with wire fencing of some sort, but if they are not needed for ventilation, you can look into these, which fill the gaps...

https://www.lowes.com/pd/Tuftex-5-P...ylene-Solid-Roof-Panel-Closure-Strips/3048079

Good luck! You've got a difficult mission ahead of you and I hope it turns out favorably.

 

[Grllcluck]

Sounds like the racoon that got three of our girls. I saw it from our kitchen window; it was running out of the coop with a hen's head it its jaws. I yelled to my husband on my way out the back door and he came running with a varment gun and the dogs.
The racoon had killed 2 and mauled another - tooth gouges and one eye either gone destroyed. Didn't eat them, just dragged them under the coop, killed them, then went back for more. With the help of our pit/sight-hound mix (she responds to the "show me" command by pointing) husband was able to find the fargin bastage with a handheld flashlight by the eye reflection high up in the tree branches. First shot winged it, 2nd shot went through it's skull.
Upshot: 3 dead hens, 1 dead raccoon. What we learned: 1) set an alarm to lock up the coop at dusk; no delay. 2) if a predator *can* get in, it *will* get in, and raccoons can tear through or finesse into pretty much anything you can think of; daily checking, reappraisal, and update of the coop & chicken yard is a must. 3) licorice, peanut butter, marshmallows are your best trap baits 4) raccoons are territorial; you may have a short grace period after getting rid of one before more find your free meat market. 5) my husband, who has never hunted and only shot his ( or any) gun a couple times to test it is apparently a natural sharp shooter - as prooved by subsequent target practice - who knew?! And 6) after trying to save the 3rd mauled hen I ruefully learned that was an ignorant, ill-advised, probably cruel, and likely dangerous thing to do. Raccoons carry nasty NASTY diseases; some communicable to humans, definitely communicable to the other hens. UNSAFE. With the luck of the ignorant the only downside to me trying to gently clean, disinfect, and save the mauled pullet was, once I did some research, we (my husband) had to put her down.
For anybody reading this far and outraged at the many stupid mistakes we made in our first year of chickens, Let me just say I WAS WRONG to try, and WRONG to think I knew ANYTHING about doctoring chickens. It still makes me sick to think about. But we did learn a lot from that disaster. And my uninformed guess is you have a raccoon problem.

 

[A.M. Eggs]

The fur I found on the door is white-ish blonde.

 

[helios]

The fur I found on the door is white-ish blonde.

Yeah, that's likely from a ginger stray cat. A gray fox would be the size of a very large cat, so would also need to squeeze through the gap and leave a little hair. The weasel's thick coat could be white/dingy white or chocolate brown with a white belly and chin, and would slink through that gap no problem.
If the necks on the chickens were broken, that suggests shaking...I'd bet few, if any, are actually broken. You mentioned blood everywhere...the weasel/mink/stoat will "ride" the prey and puncture the neck artery and let it bleed out as it moves on to the next one.
They will attack prey many times their size...full size rabbits, if that gives you an idea of their agility and determination.
If you do try to trap, fresh/bloody meat, livers, fish...etc. Stinky to cover your scent is good, and put it way back in the trap so they have to go all the way in to get it. I baited with fishy wet cat food, but didn't catch the mink with the live trap, just his confusion in the duck run.
http://www.havahart.com/weasel-baits
Good luck! Just cover any gaps 1"+ and you should be able to let your girls back in.

 

[centrarchid]

Most critters I have seen kill chickens do a few quick bites targeting neck and head. Most of time, unless taking dogs or a Coyote, there is little shaking.

 

[roosterhavoc]

Money is better spent on truly securing the coop.

If you remove the animals killing chickens they can sleep under the stars.

 

[DobieLover]

If you remove the animals killing chickens they can sleep under the stars.

Good luck with that.

 

[roosterhavoc]

Good luck with that.

Thanks. I do pretty good.

 

[Ol Grey Mare]

If you remove the animals killing chickens they can sleep under the stars.

Until the next one happens along.....

 

[roosterhavoc]

Until the next one happens along.....

I occasionally lose a bird but I have traps set 24/7 year round in and around my yard. I have plenty of free range birds that have been loose for years and have never been in a coop or pen of any kind.