King Parrots with Unusual Markings

King Parrots are easy to spot and we see them daily. The brightly coloured males and more pastel females (and juveniles, which resemble the females) all have the same markings of red/orange, green, and blue. Here's a photo showing the side and back of an adult male - notice that other than the little turquiose "racing stripe" on his wing, his wings and back are solid green:

In the last couple of years, though, I've been seeing individuals which have splashes of yellow on their backs, like this one (below):

And here's another picture of the same bird, with it's companion. I had a tough time getting these photos, as this little guy kept running up to me (looking for a treat, no doubt) and every time I tried to maneuver behind him to get a photo of his back, he turned toward me again.

Here's another bird with even more yellow:

The dark beaks on these birds show that they are youngsters. I've not seen yellow markings like this on adults, at least not yet, so I'm wondering if the yellow feathers molt out - or if what I'm seeing is simply a mutation in the wild.

I did a little research online and found some discussions about these markings. One person posted that the markings were caused by Pittascine Beak and Feather Disease (PBFD) - a virus which causes deformity in feathers and beaks, ultimately fatal. I know that PBFD is found in the wild parrot population in our area, so I searched for PBFD and King Parrot information and found another discussion forum with a posting from a person who claims to be an avian vet - and who said the same thing. Finally, I came across a reliable source - a PDF from Australia's Department of the Environment and Heritage) which confirms that yellow feathers on a normally green bird are the first "clinical sign" of PBFD.