Small Scale Units
The decision of what to do when fewer animals are involved is always difficult.
Basically, it depends on value of animals in addition to the issue of the animals concerned also being well loved pets. It can be heartbreaking to find the carnage after a fox has struck.
Whatever you do, as usual has to be done properly. It is no good buying expensive hens, ducks, pheasants, pigs etc and just shoving up a bit of mesh and hoping for the best.
Sorry - I am afraid you need to spend money to protect your investment! Shutting them in at night has to be done but many problems occur during early morning and late afternoon.
Hens & Alike
A good strong shed is the obvious choice, with a pophole that opens and closes easily.
Many ingenious ideas have been generated to control the pophole without entering the run. The run can be made of hard mesh and wooden battens on all sides and over the top if you so wish.
Remember the gateway has to be flush with no gaps. If you want a larger run then mesh can be used but it must be either dug into the ground vertically or bent over outwards at the bottom and pinned down. In each case at least 300mm/12". If money allows hot lines can be placed near the bottom and on top of the mesh.
Electric Nets
These work very well, only if they are erected properly and the grass is kept down. Ideally the grass should be cut as low as possible and the nets stretched tight betwen decent wooden strainer posts. At any change of direction a wooden post should be placed to support the net. Make sure the net has sufficient height of small holes athe bottom to stop hens scrabbling through same. The best thing with nets is they can be moved without too much hassle.
9 & 12 Line Electric Fence
If money allows this can be used without problem. The ground has to be flat and no ruts etc in the fence line. These smaller areas are where 12 line systems are usually used. The few hens are worth more in mind than commercial units? 
One visitor you can do without !
Good discounts given on all Rappa fencing products