Song Sparrow with scaly mite infection

At first this seems like a decent photograph of Song Sparrow. It comes from Dixon Lake in Escondido. Upon closer inspection, though, the legs of this birds are hideous, causing revulsive chills to run through me. I believe this is a scaly mite infection.

Song Sparrow with apparent scaly mite infection. Escondido, California. July 20, 2018.

In the past I have photographed American Robins here at Dixon Lake with this same malady.

American Robin with scaly mite leg infection

Yuck!

I thought I was getting good photos of an American Robin collecting nesting material. Then I looked and the legs were grotesque--like they were made of cottage cheese. Disgusting!

I believe that this is a scaly leg mite infection. It is cause by small mites--spider-like insects barely visible to the naked eye. They burrow under the scales on the leg. Mite infections are frequent among poultry and parrots and spread bird-to-bird or infest cages where birds are kept together.

American Robin with scaly mite leg infection. Click for larger view. Escondido, California. April 15, 2016. Greg Gillson.

The progression of the disease is rather slow. In poultry the infection is fatal if untreated. I imagine it is also fatal in wild birds. As it is building a nest, it will likely spread to its mate and future chicks.

Sad.