They should be at least 2 m X 2 m and 15 cm off the ground. Dogs, broody hens and some roosters can also be good defenders of chickens. By far the best defence is to enclose the poultry. Obviously smaller chickens are more vulnerable, keep penned until well grown. Although aviary birds are rarely directly harmed they can injure, even kill, themselves in panic when attacked.
Problems mainly occur when there is a large flight and small shelter.
If a hawk lands near the shelter the birds can feel trapped in the exposed end and panic. Aviary suggestions Cover most of the flight or have a roll-on cover handy. If the hawks cannot catch or at least see food they will not stay for long. Two layers of mesh 5 cm apart, can help. Small birds do not earth this wiring and will not get a shock.