During the past few years I have taken photographs of water birds in northwest Arkansas with suspicious reddish stain where we typically expect white. For example, I photographed two or more female Greater Scaups in which the white feathers at the base of the bill were apparently stained reddish in some way. Some females had the red, others didn't. What's going on?
I first noted a couple of these at the big water retention pond at Bentonville off Moberly Lane in March 2008. Both intrigued and alarmed, I assumed this staining was a result of getting into some kind of an oily mess.
Then I photographed a stained Trumpeter Swan at Holla Bend NWR (March 2010). In 2011, I photographed a Trumpeter Swan sitting on a nest at Boxley, in the Buffalo Valley (June 2011), long neck heavily stained reddish. Swans that spent a few days at Har Ber Meadows in Springdale (Feb 2011) were stained, as was a female Lesser Scaup this fall at the state fish hatchery in Centerton.
None of us expect to see such oddities. With the big BP oil spill, and with environmental problems associated with increased oil drilling elsewhere, I have felt quite a bit of alarm about seeing these birds.
I ran some of these photographs by David Krementz, leader of the Arkansas Cooperative Fish & Wildlife Research Unit (UA-Fayetteville). He followed up by contact with a noted waterfowl research expert, who forwarded a technical paper dealing with what is termed "marsh stain."
Folks who have looked at this phenomenon term these "adventitious stains." Many are caused by contact with naturally occurring chemicals or other matter in the environment. They have been noted in 120 species. Apparently the birds often acquire this rust color while excavating foods encrusted with oxides of iron. It doesn't take long to stain white feathers.
The fact that marsh stain is common doesn't mean that all the birds seen with stained feathers could only have acquired it by contact with iron oxides while foraging. For example, it doesn't rule out unplanned contact with oil. But, that said, marsh stain seems a reasonable explanation, and best of all, well- supported by evidence.
Finally: It is worthwhile to keep watching and to keep checking out what we see that doesn't add up.