predators

The only sure way to keep your birds protected is a covered run. As long as you free range you take the chance of losing birds to predators.

 

Unfortunately silkies, with their topknots seem less likely to evade hawk attack than some of the other breeds with better vision.
Your best bet is a covered run, as has been mentioned. I also know people criss cross wire over their runs, not as effective as a totally covered run but better than uncovered.
Lots of plants and trees and places for a chicken to hide will also help.
Some people feed and encourage blue jays and crows which tend to annoy hawks,
Do you know what kind of hawk the predator was? I've heard of people encouraging the smaller hawks which find chickens too large to prey upon in the hopes they will annoy the larger hawks.
I also know some people who free range their chickens in pastures with goats, cows or horses as the larger animals are a deterrent to a hawk's descending on a chicken.
Nothing protects like a covered run, but if you don't have that there are a few other steps you can try.
We have covered runs, but when our chickens were out, nothing ever got them when the dog was out with them.

 

X2 on keesmom's post.