In the column Since You Asked in every issue of BirdWatching, Contributing Editor Julie Craves answers readers’ questions about birds and bird behavior. Here’s a question from our February 2018 issue.
Why do male Ruffs have so many different plumages? — Edward Peters, Springfield, Massachusetts
Calidris pugnax is a medium-size shorebird that breeds across northern Eurasia and winters in Africa and coastal areas across the Old World. Every year, some stray to North America, usually on the coasts and typically during spring and fall migration. Females Ruffs are sometimes called “Reeves.”
Reeves are unassuming, with what could be considered the standard brownish, scaly-patterned sandpiper plumage. Males outside the nesting season have a similar appearance. But breeding males can be spectacular, with bouffant head plumes and elaborate fluffy feathers around the neck (in a ruff, hence the name). Many males have primarily dark plumage featuring black, brown, and rust colors, while about 20 percent of males are mostly light-plumaged with white, straw, or gold feathers. Different patterns and combinations of solid colors and patches, barring, or flecking can occur, earning Ruffs the distinction of having the most extreme variation in individual plumage of any bird species. A handful of males never develop fanciful plumage, and look very much like females.
Dark versus light plumage appears to be under genetic control and is linked to breeding behavior. Ruffs utilize leks — places where males gather to display and attract females. Dark males establish and defend small courting spaces in leks. Light males share the leks, engaging in displays but not defending territories. The rare female-plumaged males visit leks but do not display, waiting for surreptitious mating opportunities. Each male has the same role throughout its life.
Females visit leks and choose male partners. Most females mate with more than one male. Usually the matings occur with males of both color forms, so the exact evolutionary driver for the variability between and among dark and light males remains unclear. Individual recognition may help females choose particular males or help neighboring males avoid other territorial males.
About Julie Craves
Julie is supervisor of avian research at the Rouge River Bird Observatory at the University of Michigan Dearborn and a research associate at the university’s Environmental Interpretive Center. She writes about her research on the blog Net Results, and she maintains the website Coffee & Conservation, a thorough resource on where coffee comes from and its impact on wild birds.
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