
I can see droppings both brown and white (yes the white is urea which in mammals would be liquid urine). I can also see bits of broken feathers and scales.
First, as Robert says, you need to keep them cleaned out more frequently - it's difficult at this time of year because they are indoors so much that most of their droppings land in the house under the perch, rather than outdoors, so they need to be cleaned out more often than in the height of summer. The smell of ammonia will build up rapidly and affects the birds, so don't let it get to that stage if you can help it.
Secondly - are they moulting? That could explain the white debris, but I would also check closely that they don't have any parasites such as scaley leg mites, lice, red mites and so on, and obviously treat them for that and give the house a thorough clean. The debris might just be bits of feather and scale, but it could also be a sign that they are preening far more vigorously than normal while on their perch as a result of a parasite. There's no harm in giving them all a good spring clean at this time of year - the hens that is

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Egg production will be low at this time of year because of the short days, but it should start to pick up in a couple of weeks (I hope it does anyway as we have a lot of hens but hardly any eggs

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