This is a study (a bit long and a bit arid if you are not into reading this kind of thing) about the microbes that live on the skin and feathers of wild birds. The thing is that there have been many studies about birds intestinal bacteria and even feather bacteria (as well as myriad ones about the bacteria found in human skin) in the past but they were all about domesticated species (like chickens), never done on wild birds of different species until now. And what they found is that there is a relationship between the host species and the microbiota found. This tells us that there is a host/parasite link so, basically, the kind of bacteria that, say, a sparrow would have is not the same as what a starling would even though they live in exactly the same natural habitat. How cool is that?!
https://www.nature.com/articles/s41396-019-0438-4