March 20, 2009 -- Female finches from Northern Australia are controlling the sex of their offspring, according to the hair color of their male counterpart. The finding, published today in the journal Science, is one of the first to clearly show that birds are capable of biasing the sex of their offspring to overcome genetic weaknesses. Lead author Sarah Pryke, of the Department of Brain Behavior and Evolution at Macquarie University in Sydney, admits the mechanism by which the birds do this is not yet known. The endangered Gouldian finch (Erythrura gouldiae), which is found in the northern savanna's of Australia, can have either black or red heads. Pryke said some genetic incompatibility between the black and red-headed birds results in high mortality in the offspring when birds of different head colors mate. Related Content: With female offspring this mortality rate can be as much as 80 percent higher than in a same-head color pairing. Sons in a mixed pairing have a 40 percent mortality rate. Pryke found that if the female mates with a finch of different head color, she attempts to overcome this genetic incompatability by over-producing sons -- as many as four males to one female. "This is the first time such a large effect has been shown," said Pryke. "It is actually the female that is controlling the gender." To reach this conclusion Pryke and colleague Simon Griffith took 100 red-headed and 100 black-headed female birds and mated them with a male of the same head color and a male with the different head color. They found females in mixed pairs produced broods that were 82.1 percent male, whereas females in matched pairs produced an unbiased sex ratio with 45.9 percent males. They then tested whether the females in mixed pairs were deliberately over-producing sons. Female birds were tricked into thinking they were mating with an incompatible male. The researchers did this by temporarily blackening the head color of red males and mating them with red and black-headed females. Get More NewsSpiders, Scorpions Among World's Oldest CreaturesMany creepy crawlies have been on Earth much longer than previously believed.Blood-Sucking Vampire Bats Sing DuetsWhite-winged vampire bats "harmonize" with separated roost mates.Oldest Hebrew Writing Possibly FoundAncient inscriptions on a 3,000-year-old pottery shard could make history.Rare, Prehistoric-Age Reptile Found in N.Z.A tuatara has been spotted on the New Zealand mainland for the first time in 200 years.Iceman Has No Living RelativesOetzi, the 5,300 year-old frozen mummy, left no living genetic legacy.SLIDE SHOW: Landscapes of TerrorWhat makes a place feel scary? There are scientific explanations.It's Official: People Are Warming the PolesHumans are conclusively to blame for polar warming, say scientists.Eight-Armed Animal Preceded DinosaursWhat may be one of Earth's first animals was no bigger than a coaster and had eight arms.Phoenicians Live on in People's GenesOne in 17 Mediterranean men may be descended from ancient Phoenicians.Pesticides, Fertilizers Linked to Frog DeclineA pesticide is found to promote parasites among amphibians.Hubble Telescope Taking Photos AgainThe Hubble Space Telescope is once again snapping stunning photos of the universe.Andean Mummy Hairs Show Hallucinogen UseScientists find direct evidence of hallucinogenic drug use among ancient Andeans.Opals on Mars Reveal Planet's Long Wet PastOpals found on Mars suggest the planet has been wet for much longer. |
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