Many birds molt feathers twice a year, before the breeding season (and spring migration) to enhance their sex appeal and gain maximum aerodynamic efficiency, and again after the breeding season is concluded, to become more cryptic and less vulnerable to predation.
Sandhill Cranes have a different strategy; they take a mud bath by preening iron-rich mud into their breast and back feathers during the breeding season, in order to become the “little brown crane” of the early ornithology literature. At the end of the breeding season this coat of brown feathers is shed as new gray body and wing feathers are molted.
The difference in their coloration from fall to spring is striking.
Apparently cranes love mud, and will immediately start mud-preening when presented with a suitable substrate — even if it is from a bucket of mud placed in their zoo crane pen!
Is this an attempt by the cranes to become more cryptic at a vulnerable time in their life cycle — while they are incubating and molting flight feathers?
Or is the feather dyeing behavior an attempt to rid the bird of irritating feather parasites? Many birds take “dust baths” to suffocate those little pests in their feathers which they then preen out. And what is the significance of preening themselves with iron-rich mud; does iron retard ectoparasite activity?
Here’s what D.O. Hyde had to say about this in 1968: Adult cranes stain their plumage “as an intentional desire to change the color of the feathers associated with the act of pairing or connubial bliss”.
Nah….I’m not in favor of that explanation. What about you?