Chook stealing dilemma?

OK this is my problem. I have had my chooks for serveral years now without any issues. In the last few weeks I have lost almost all of them. I live on a farm and the chooks put themselves to bed by roosting in a tall tree outside my bedroom window. In the last few weeks they have been disappearing overnight. My first theory was that the early rising chooks were getting out of bed predawn when foxes were still lurking and subsequently getting taken by foxes. HOWEVER, last night was different. I woke at 2AM to find a heist underway. Somehow a fox or similar animal had coaxed my favorite white chook from the tree and was chasing it, its cries awoke me. Now I don't know if it was a fox because it was too dark to see but after the animal and disappeared with the chook a fox came back and was lurking in the bushes near my house (I chad by this time turned the outside lights on and could see). So my question to you is - if a fox is the only creature involved, how the hell did it manage to get my chooks from the heights of the tree they roost in in the middle of the night. AND, is it possible that the fox that was lurking after the incident was innocent and some other animal was responsible for the stealing? (I know there are wild cats in our area, - Australia NSW) Any insights to solve this mystery would be good considering that there is no way a fox would climb the tree and the chooks would hardly voluntarily jump fro the tree at such an hour!