It is not unusual to see chickens moulting in winter despite the fact that it appears to defy all logic. Why would chickens want to lose their feathers just when they need them most? Moulting in winter seems to be quite common, however as it does appear to go against the usual efficiency of mother nature, it is worth considering what factors might be causing the moult.
The obvious culprit responsible for this apparent winter moult might be lice or mites and you should check carefully for these and take action to remove them immediately, paying particular attention to the area below the vent, under the wings and at the base of the tail.
If you are happy that your chicken does not have lice or mites then check that she is not displaying any other signs of illness such as breathing problems. If she appears to be her normal healthy self then consider whether the feathers may have been lost as a result of fighting with her peers or from an encounter with an over enthusiastic rooster.
Another point worth considering is whether you have changed your chicken’s diet recently and the feather loss has happened subsequently.
In the majority of instances chickens will only experience a partial moult when they lose feathers in winter. Very often the birds will only be in their first year of life and many growers may have up to three partial moults in the first year. In addition when the birds have a partial moult, their owners will notice no or very little reduction in egg production.
Some other points regarding winter moulting that we have noticed over the years is that birds who are bred for high egg production often do not actually have a full moult in their first year, but instead have a partial moult when they are a year old, no matter what time of year it is. Of course in the natural state birds would only be born in late spring and summer and therefore their annual moult would also be at that time of year. But chicks of course can be artificially reared at any time now.
In addition if the birds have been bred for high egg production the chances are that those who do not have a full moult and stop egg production for a period of time, will be favoured when it comes to breeding stock, thereby passing on the tendency.