Snakes are common predators found where poultry are kept, usually due to multiple snake attractions---eggs, birds, rodents, and shelter. There are many different species of snakes, both poisonous and non-poisonous---both of which can cause harm to your flock as well as yourself and your family.
Snakes are predominately attracted to eggs, as they provide the easiest source food with the least threat of harm or effort. They are also masters at breaking into even the most robustly protected chicken coop---due to their highly flexible skeleton that allows them the ability to squeeze through holes you could never think that a snake could possibly fit through.
Depending on the size of the bird, and the size of the snake, snakes can also eat members of the flock, especially bantam-sized breeds and young birds. Due to the unique design of the snake's jaw bones, they are able to open their mouths very wide and move each jaw independently. Thus, allowing the snake to swallow prey larger then their own bodies, by "walking" their mouth around the bird from side to side in a forward motion. There have also been many incidences where snakes have killed birds in an attempt to consume them, however either get interrupted or realize that the bird is indeed too large for them to consume.
Snakes are cold-blooded ectotherms, meaning that they must control the temperature of their bodies through their behavior in order to absorb or give off heat. This is why snakes often seek shade during the hottest portion of the day, and are attracted to roads during cooler days where they obtain heat from the road surface.
Eliminate access points : All openings larger than 1/4 in (0.6 cm) in size should be sealed shut.
Check corners of doors and windows, as well as around water pipes and electrical service entrances.
Snake-proof fencing : A fence can be made from 1/4 inch mesh galvanized hardware cloth, 30 inches high.
The bottom edge should be buried at least 6 inches in the ground and the support stakes should be inside the fence to prevent snakes from crawling up them. Such a fence also can be added in front of an existing fence.
Gate fittings and doors : Any gates should fit tightly and be kept closed when not being used.
Fence maintenance : Regularly inspect the fence to be sure that holes haven’t been opened under it, and that items have not been piled against the outside.
Keep landscape well-trimmed : Regularly mow grass to keep height down
Remove snake hiding spots : Eliminate wood piles, boards, rock piles, and any items that could provide snakes with a place to hide underneath.