Well, kind of embarrising to say but, Rats... LOL the littlest creatures, but they sure get mean when I have little ones in the coop and taking the grain out at night. The got my gosling just bit her a few times, but they killed my sons call duckling that he was going to show later this year or next years spring shows, they also bite a couple of the other ducklings. They were not super little babies either, almost fully feathered and doing great. They are all doing well now, healing up and very protected, they have never gone after any of my adult birds, yet anyway. I have gone all 100% poison free trying to tackle the buggers.
We have an old abandon blackberry vine covered house next door that god only knows what lives in there, along with some old sheds on our property. I have traps set and rotate them often as they are very smart and will avoid them sometimes.
I have only ever had one other full size bird get killed abou 3-4 years ago by a racoon, it killed it right through the chicken wire. Last year I had problems with the rats killing my quail, they have to be caged differently so the set up I had just wasnt working and I could let anymore get killed so I sold them all. I really miss them, hopefully this summer/fall/winter I will be getting a new shed built to house my chicks show chickens and such in to keep them a little safer, in the mean time I am building new pens for them above ground and the ones that will stay on ground putting down wire mesh then covering it with about 5inches of wood chips, this way they can not make there tunnels into my pens anymore.
It really sucks to have them but they love the grain, its that or just keep on feeding them, they are so gross though. I have a friend who works for Orkin (I believe thats it) the pest control, and shes helped me out with traps, and bait stations and mentioned making me some traps like one she made to trap a racoon she had at her place.
I am determined to get them GONE! This is why I have sold what I possably could part with now, so I could get some extra $$ to buy my 5 year old some more ducks so he can show with me and hatch and raise them himself.
I have a nice handful of chickens and a nice handful of ducks left now.