Do Some Birds Cheat to Avoid Inbreeding?

<< Back to Page 1   Page 2 of 2

That assumption fell by the wayside as DNA testing showed that female promiscuity is far more common than monogamy.

"Since [1988] there's been a gradual recognition that females must be getting some benefit from seeking multiple partners," said Judson. "In the last five years there's been a quite vigorous search to explain the reasons for cheating on part of either partner."

One explanation is the "good gene" theory; females might want to pair up with a guy who will be a good provider, but if she can also mate with the guy with the brightest feathers, the longest tail, the biggest horns—and get away with it—she'll go for the good genes, too.

The shorebirds study suggests that avoiding genetic incompatibility is another.

Extra Pairing in Shorebirds

Researchers from six countries studied three shorebird species—western sandpipers, Kentish plovers, and Common sandpipers—that are both socially and genetically monogamous. Partners in the three species share incubation duties, and males provide parental care after hatching.

"Social monogamy is about who's tending the nest; genetic monogamy is what's going on in the clutch," said Sandercock.

Chicks with mixed paternity—not the offspring of both partners tending the nest—were found in less than 8 percent of western sandpiper nests, 5 percent of Kentish plover nests, and 20 percent of Common sandpiper nests.

"This is quite different from some socially monogamous songbirds like tree swallows, where you might find up to 40 percent of the chicks in a nest are the result of extra pair matings," said Sandercock.

What would drive a normally monogamous bird to seek additional mating opportunities?

"Incestuous matings bring on infidelity," said Sandercock, in summing up the research. "What's amazing is that we found this to be consistent across all three species."

Figuring out the different reasons that mates cheat will no doubt occupy scientists for years to come.

"Of all of the different hypotheses to explain what benefits females are getting from cheating on their mates, I think avoiding genetic incompatibility will prove to be the most widespread," said Judson, whose book, Dr. Tatiana's Sex Advice To All Creation documents the numerous strategies different species have adapted to achieve reproductive success.

"Incest is one form of incompatibility," she said. "But I think that we'll find many instances in which neither partner in a couple is sterile, but the partners together are genetically incompatible."

The shorebird study suggests several avenues for future research, said Sandercock. Identifying the consequences of inbreeding, the social constraints that cause genetically similar individuals to become partners, and how the birds identify a closely related mate are all missing pieces to the puzzle, he said.

Judson has her own question.

"Why is it that these birds are usually monogamous? They're living in colonies, and have the chance to cheat; what are the possible disadvantages to cheating?"

Recent Bird Stories by National Geographic News:
Birder's Journal: A Morning With Migrants
Water-Diversion Plan Threatens California's Salton Sea
500 Most Important Bird Areas in U.S. Named
Birder's Journal: This Warbler Is a Master of Deception
Bald Eagles' Manhattan Return Turns Turbulent
Birders Journal: Attack of the Flying Goshawk
Saving the Edible-Nest Swiftlet
Birder's Journal: Seduced by Dueling Thrushes
Birds Can Be Picky About Their Neighborhood, Studies Find
Acid Rain May Have a Role in the Decline of the Wood Thrush
Icelandic Kids Save Befuddled Puffins
Crow Makes Wire Hook to Get Food
Rare Warbler Eluding Extinction in U.S.
In India, Nets Save Baby Storks From Falls
Bald Eagle Bounces Back After Decades of Persecution
Birder's Journal: It's Survey Season for Breeding Birds
Conservationists Fight to Save Harpy Eagles
Birder's Journal: Chasing Down Warblers
Africa's New Safari Trend Is for the Birds
Decline of Red-Tailed Hawks Has U.S. Scientists Puzzled
A Reason to Give Thanks: The Return of the Wild Turkey
State Bird of Hawaii Unmasked as Canadian
Harry Potter Owl Scenes Alarm Animal Advocates
Ultrarare Woodpecker Spurs Ultimate Birding Trip
"Extinct" Woodpecker Still Elusive, But Signs Are Good
Extinct Dodo Related to Pigeons, DNA Shows
Bird Extinctions May Hold Clues to Human Survival, Author Says
Tagging Hobbles Penguins, Some Researchers in Cape Town Contend
Patagonia Penguins Make a Comeback
Penguin Decline in Antarctica Linked With Climate Change
Ice Buildup Hampers Penguin Breeding in Antarctica
Evolutionary Oddities: Duck Sex Organ, Lizard Tongue
Some Ducks Let Young Be Raised by Relatives
Turkey Vultures Flourish in the U.S. Thanks to Road Kill
Forecasting the Journey South

National Geographic Bird Resources:
Bald Eagles: Come Back From the Brink
Experience the Sights and Sounds of Eagles Bird-Watching Sites:
Boston Area
Chicago Area
Florida Keys Area
Maine's Acadia National Park
Mount Rainier
New Orleans Area
New York City Area
North Carolina's Outer Banks
Philadelphia Area
Portland Area
Rocky Mountain National Park
Salt Lake City Area
San Francisco Area
Santa Fe Area
South Dakota's Black Hills
Washington's Olympic National Park
Wyoming's Grand Teton National Park
Yellowstone National Park
Yosemite National Park

From the National Geographic Store:
Guide to North American Birds
Portable Birdsong Identifier
Birder's Journal
Songbirds Puzzle

Additional Information from Related Web Sites:
American Bird Conservancy
Fish and Wildlife Service Bird Web Site
National Audubon Society
Environmental Protection Agency: Bird Conservation

<< Back to Page 1   Page 2 of 2




NEWS FEEDS     After installing a news reader, click on this icon to download National Geographic News's XML/RSS feed.   After installing a news reader, click on this icon to download National Geographic News's XML/RSS feed.

Get our news delivered directly to your desktop—free.
How to Use XML or RSS

National Geographic Daily News To-Go

Listen to your favorite National Geographic news daily, anytime, anywhere from your mobile phone. No wires or syncing. Download Stitcher free today.
Click here to get 12 months of National Geographic Magazine for $15.