Mites problem?

Hi Brownwing, it can be a common problem amongst garden birds ranging in minor balding to more severe cases and is most often due to mites in their nesting location, however, hopefully in a couple of months this bird will go into its annual moult and start to grow new feathers replacing the old ones that are left and will cover all the bald patches. At this time of year birds are not looking at their best after a busy breeding season and some nests, both naturally made and provided nest-boxes can get mite infestations. All bird boxes (if you have any) should be taken down in the autumn, September onwards, scrubbed out with soapy hot water, thoroughly rinsed, air dried and then replaced back in situ before the colder winter months so birds can use them to roost in.