If she is standing with her neck tucked in, it just means that she is feeling ill. Usually sick birds struggle to maintain their body temperature even in warm weather so she may benefit from being on a heating pad. A warm shallow bath in Epsom salts (just up to her tummy) in a washing up bowl or plastic tote and gentle massaging of her soiled feathers with a mild soap should both warm and clean her up and dry thoroughly with a hair drier, but be careful not to get it too hot.... what is comfortable for you will be comfortable for her.
Feel her abdomen for any unusual swelling and compare to your other chickens if you are not sure.... you can do this on the roost at night if they are not good at being handled. Assess her body condition.... how pronounced is her breast bone.... again compare to other chickens.
If she has lost weight there are a few common things that come to mind.....
1. Coccidiosis..... unusual in a bird of that age unless she has recently been rehomed and exposed to a different strain of cocci than her body has previously developed resistance to. Coccidiosis will cause diarrhoea, usually mucous like in consistency or bloody.
2. Worm burden..... worms will obviously take the nutrients out of her gut and therefore prevent her from gaining any benefit from what she is eating and hence lose weight.... they can also cause an impaction in the digestive tract resulting in the bird being unable to eat much. Fluids can however pass through the system causing diarrhoea.
3. A partial crop or gizzard impaction can also result in mostly fluids going through the system and the bird losing weight.
4. Internal laying, Egg Yolk peritonitis, salpingitis, or a tumour can put pressure on the digestive tract causing a partial blockage, leading to diarrhoea and the bird feeling sick. Usually with these there will be some abdominal swelling often quite significant and the bird is unlikely to have laid an egg for quite a while before it becomes noticeable.
If you can find a local vet or laboratory ( some do mail order) that will test a faecal sample for worms and coccidiosis, that will help to rule out 1 and 2 above. The bird does not have to be examined to have these tests done on a sample and the cost should be about £10-15. It is not a good idea to medicate a sick bird with something they don't need, so better to rule these out with a test than use a wormer or Corid, just in case.
For No.3 feel her crop in the evening and remove access to food at roosting time, then again check again first thing in the morning. It should be full at night and empty in the morning. If it is still full in the morning she may have an impaction...sometimes it will feel hard but most of the impactions I have dealt with were squishy. If she has sour crop her breath will smell bad, but you can have an impaction without it turning sour. Liquid feeds and regular crop massage may help
Unfortunately there is not a lot that can be done for the problems listed in No. 4. Sometimes antibiotics will help short term, but the prognosis is not good.
Let us know what you find and we will try to help you further.
