I have shot many Grebes, I have noticed that these guys get a rust like color or substance as seen in the photo, around the front lower chest area, I have often wondered what this is and what causes it but never got around to asking anyone..
Thanks..
Rust is pretty close to the mark. There is an iron-fixing bacteria present in the sediment of wetlands in many areas. They produce a stain that adheres to the plumage of birds that frequent these areas. Look at the faces of snow geese and tundra swans in California or northern Alaska for example. BUT, I don't think I see this on the grebe at the start of this thread. At low-res this looks like bits of vegetation?
The most likely cause of of this 'staining' (IMO) is incubation duties of the bird. A grebe nest is, in essence, a pile of rotting vegetation & this will explain the pieces also noted by Declan. I've just been looking at some of my breeding auk images & some show similar discolouration.
Thanks for the replies!
I have to say though that I am still a bit stummped with this, as I have photos of just about every diving duck, grebes etc.. They all get this, but only in the local waterways inland.
I never see them in the ocean with this, The above photo is a mild patch, I do have many that have it much thicker, It does seem to start at water level (nothing above or out of the water) ..
Thanks again.