Assuming the field is of adequate size and has sufficient grass, here are some points to consider when wintering your pony out.
Check the field for poisonous plants (ragwort, hogweed, laurel and yew) and remove them. They should be burnt after removal.
Check the fencing. Mend broken fences appropriately – string and barbed wire are not a suitable solution. Treat wood to prevent rot and chewing.
Check that the height of the fencing is sutiable for the height of the animals you expect to winter out. Post and rail fencing which is 3ft high is not suitable for shetlands!
Is there appropriate shelter? Most trees lose their leaves in winter, while dense hedges can be wind breaks all year round.
If usinga field shelter check that it does not leak, and that it has no protruding corrugated iron, nails or wire etc. The wood will need treating to conserve it – creosote is cheaper than cribbox and just as effective.
Check which type of animal has grazed there previously and what will be grazed in adjacent fields. Warning – donkeys are thought to carry lungworm, while cows carry ringworm that can live in the wood.
Will the ponies have access to fresh water? Is it on the mains or a water meter and who owns the troughs? Metal troughs rust and can have sharp edges. Think this through as buckets are heavy when full and can be easy to knock over.
What about access to the fields. Do you need to unload on a main road or is the gateway suitable for a lorry or trailer? Would a vet be able to reach you easily in an emergency?
Is the field secure? Is it isolated or in view of the road? Secure gates with thick chain and padlocks. Fields with public footpaths through are not generally good news as passers-by tend to feed unwanted items to ponies.