Careless whispers cost chicks
Females stray when mates lose song
3 May 2002
|A male chickadee
|© D. Mennill
Female birds that overhear their partner lose a singing
more likely to mate sneakily with another male, researchers have found1.
Just two defeats send a female looking for alternative
are deciding who's going to father their children on the basis of a
interaction," says zoologist Tom Peake of the University of Copenhagen,
Denmark. "That's got to worry pretty much every male on the planet."
Female eavesdropping shows that there's more to fighting
the combatants know who's boss - everyone within earshot is also
Daniel Mennill of Queen's University in Kingston,
the woods to do battle with male black-capped chickadees (Poecile
He provoked the birds using a laptop loaded with song recordings.
Against half the males, Mennill was the aggressor,
the same time and pitch as the singing male. This stops them getting
message across, he says.
He showed subservience to the other males, waiting until
singing and then broadcasting at a higher pitch. This signifies low
in a real male.
being a chickadee.
Mates of the high-ranking males Mennill defeated were
more likely to breed with other males, DNA tests showed. "It's probably
quite a shocking thing for females to hear - they're accustomed to
males winning every fight," he says.
Chickadees form pairs to raise a family, but they are
In the wild, about one in three broods contain chicks sired by a male
than the female's mate. Chickadees live in flocks with a strict pecking
order; females paired with low-ranking males are more likely to seek
"There's growing evidence that males and females
He has found that male Siamese fighting fish are more aggressive
males they have seen win a fight.
Watching a fight gives fish a testosterone rush. The
football spectators: "Their hormone levels go all over the place
on which way the match is going," says Peake.
Being watched probably also changes behaviour. The
reputation might make witnessed fights more violent.
On the other hand, if neither contestant is sure of
want to conduct their battles in private. This could explain why, in
thrushes and robins, the longest song duels are the quietest, says