 | Biologist Wiebe discovers woodpecker hanky-panky
By Kristina Bergen
Appeared in On Campus News, January 10, 2003
During field studies in northern B.C., U of S Biologist Karen Wiebe found the first recorded case of a female woodpecker taking a second mate while still with her initial mate.
Ninety per cent of bird species are socially monogamous but with woodpeckers, tracking their sex lives is a bit like watching a soap opera.
As part of the largest and most intensive population study of woodpeckers in Canada, University of Saskatchewan biologist Karen Wiebe has discovered the first recorded case of a female with more than one male mate (polyandry) in a North American woodpecker, the Northern Flicker.
The discovery will be published in the spring issue of Wilson Bulletin, a quarterly publication by the Ornithological Societies of North America.
Early last spring, a male lost his female and started calling, advertising for a new mate. The couple next door lived only 300 metres away and the enterprising female responded to the call, mating with both her resident male and the lonely widower.
She helped with the incubation and brooding of each clutch, laying seven eggs in each of the male's nests at staggered intervals. The result was 14 healthy chicks in one season, double the reproductive output of a normal monogamous female.
Color-banding the birds allowed Wiebe to track each member of the love triangle and study the unusual sex differences in gender roles. For example, male flickers build the nesting cavities and do most of the work incubating eggs. This leaves the females more time to search out the best mating partner, which isn't always the resident male.
"Females want the best genes for their offspring, but probably have to sneak around so resident males will maintain an investment in the clutch and incubate all of the eggs," said Wiebe.
Female flickers may prefer older males because they have proven their ability to survive, a necessary quality for a species in which the males are the dominant care-giver.
But DNA tests prove that males are not exempt from dabbling in a little woodpecker hanky-panky.
"Blood samples from parents and their supposed offspring tell us that some chicks are related to the female but not the male, which means the female has run off to copulate with a strange male," said Wiebe.
"Other chicks are related to the male but not the female, which means the male has run off to copulate with a strange female, who then returns to dump the egg in the male's nest without the resident female knowing about it."
The ongoing flicker study, funded by NSERC (the Natural Sciences and Engineering Research Council), takes place on an abandoned military base near Williams Lake, B.C., which has been turned into a grassland grazing area.
The attraction of this particular area is aspen groves, the tree of choice for the Northern Flicker.
"Flickers like to live in grassland areas with many clumps of aspens," said Wiebe. "They prefer to excavate cavities in these trees, which rot from the inside out, so all they have to do is break through the tough outer layers of the tree and carve a nest cavity in the soft interior wood."
Northern flickers are recognized as a "keystone" species in boreal forest ecosystems because they often abandon their tree cavities after one season, providing homes for other birds and animals such as bluebirds, owls and squirrels.
In the next few years, Wiebe plans to attach small weights to one mate in a pair in order to track how much one partner is willing to compensate for the energetically stressed mate while foraging for food to feed nestlings. She expects some, but not total, compensation.
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