Fox Threat - Housing Estate

I am getting to welsh harlequin duck in June and currently building their pen and cage.
We live on a housing estate which is pretty built up, the ducks will be locked up at or prior to dark.
Currently their run area be the alley down the side of our house with the cage in an area to the side with decking and a permanent 1/2 meter sqr pool.
The alley has a 10ft wall one side and a 10ft fence the other with a 6ft gate at the end, there is no cover on this area.
The area where the cage and decking is has a 4ft wire fence and again no cover.
We will let the ducks run freely in the garden when we are about.

It will not be a straight forward job to make this area fully fox proof and I was wondering what treat will be from foxes in day light hours.

We sometimes leave our rabbit out all night with no problem and have never ever seen a fox in 5 years of living here.

Any feedback would be great

Regards
Darren

My ducks are always locked up at night but they free range in the garden during the day. I am also on an urban estate and the garden is surrounded by a 6' fence. I have never seen a fox round here in 8 years and have never had a problem during the day but I know for a fact that there are foxes round here and they can get over a 6' fence as last year I lost 2 ducks and had 4 more injured by a fox one night when the wind had blown open the pen door that I hadn't secured properly (not and event that will occur again!).  I still let them free range during the day as I didn't get them to be battery ducks but I have to accept the small risk that a fox will cross at least one other garden and a 6' fence in broad daylight to get them. Not had a problem in 2 years and hope I never do but I think the risk is small during the day and am happy to live with that as they are so happy in the garden.

I hadn't seen a fox in 3 1/2 years of living where I do. The night after we got our girls, guess who turned up at 4.30 am? They're everywhere I tells ya 

exactly what happened to us.

I know that all sounds very alarmist but in the 6 months since I lost my girls I have not had a problem leaving them to free range during the day. Would never leave them unsecured at night.