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The signs you are describing may go with a number of generalized problems such as:
At this point your best option is to have him examined by an avian vet. Try www.aav.org/vet-lookup, or http://poultrykeeper.com/poultry-vets-uk/poultry-veterinary-practices-services-uk/.
Until your appointment, please isolate in a safe, well-enclosed small area to limit his exercise, with his favorite foods and water made easily available.
There are no safe or effective OTC products to use.
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