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Bright beaks equals delight for ducks

By Ruth Hendry - 14 Apr 2011 7:58:1 GMT
Bright beaks equals delight for ducks

How do you know how to pick a mate? Best body? Big car? Lots of money? Female mallards have their own unique way of determining which mate they should choose.

Females of all species want to pick the best father for their offspring. This is the male with the best genes, who will produce successful, healthy children. But what if the male carries an STD? How does the female of the species know? In mallard ducks, there's an easy way to distinguish between males' resistance to sexually transmitted bacteria. The brighter the male's beak, the more effective their sperm's antibacterial properties.

A study released today shows that mallard duck sperm has antibacterial activity - it can kill E. coli! That's good news for female mallards. E. coli can damage a male's sperm and decrease its reproductive success. If E.coli is passed to the female, it could weaken her and affect her ability to care for her offspring.

This means that it's advantageous for female mallards to identify males with ''superior'' sperm. Mallard beaks range in colour from a dull green to a sunny yellow. Females tend to prefer males with bright yellow beaks. Scientists think that females prefer brighter beaks because it signals that the male mallard is fit and able to produce healthy offspring. Beaks are coloured due to carotenoids - the same pigments that make vegetables brightly coloured. More carotenoids leads to a brighter bird beak.

Scientists experimented to see if carotenoids levels, and therefore beak colour, are correlated with antibacterial properties in male mallard's sperm. They found that the brighter the beak colour, the higher the antibacterial properties of the mallard's semen. This means that female mallards have an easy way to tell which male's sperm is healthiest.

What next for scientists now they’ve found out the bacteria killing abilities of duck sperm? They still haven't found out what part of the mallard semen gives it antibacterial properties, so identifying this is the scientists' next project. Next time you buy some bleach from the supermarket, watch out for that hidden ingredient...