What kind of Predator?

[NickGT]

I have 5 Pekin ducks that are about 8 months now. Had them their whole life and never had to put them up. First time last night one of my ducks was attacked at the back of the neck. It seems ok. None of the others were attacked. What would bite the neck but not kill it?
Pic for reference.

 

[Trish1974]

Mink and weasels go for the neck. The duck is lucky it survived, and that no others were attacked. Make sure to cover any holes or gaps smaller than a half an inch. Whatever it was will be back.

 

[aart]

Had them their whole life and never had to put them up.

You mean you don't have a secure coop and/or run?
Guess you need one now.

 

[ellenscoop]

Have you tried using poultryDVM's poultry predator identifier tool?

 

[Bryant Redhawk]

From your description it could have been; Owl, fox, raccoon, weasel, skunk, mink, or opossum for starters. Any one of these predators will go for the neck to do a quick kill.
The fact that your duck is alive just means it was extremely lucky. As others have mentioned, it will be back and it will continue until there are no more ducks left or you take steps to make it so the critter can't get to the birds.