Careless whispers cost chicks
Females stray when mates lose song
battles.
3 May 2002
JOHN
WHITFIELD
 |
| A male chickadee
risks
his reputation. |
| © D. Mennill |
|
|
Female birds that overhear their partner lose a singing
contest are
more likely to mate sneakily with another male, researchers have found1.
Just two defeats send a female looking for alternative
mates.
"Females
are deciding who's going to father their children on the basis of a
six-minute
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
than
letting
the combatants know who's boss - everyone within earshot is also
picking
up information.
Daniel Mennill of Queen's University in Kingston,
Ontario,
went into
the woods to do battle with male black-capped chickadees (Poecile
atricapilla).
He provoked the birds using a laptop loaded with song recordings.
Against half the males, Mennill was the aggressor,
playing
songs at
the same time and pitch as the singing male. This stops them getting
their
message across, he says.
He showed subservience to the other males, waiting until
they
finished
singing and then broadcasting at a higher pitch. This signifies low
status
in a real male.
 |
| Daniel Mennill
plays at
being a chickadee. |
| © Stephanie
Doucet |
|
|
Mates of the high-ranking males Mennill defeated were
significantly
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
their
males winning every fight," he says.
Chickadees form pairs to raise a family, but they are
not
always monogamous.
In the wild, about one in three broods contain chicks sired by a male
other
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
out
other mates.
Spectator sport
"There's growing evidence that males and females
eavesdrop,"
says Peake.
He has found that male Siamese fighting fish are more aggressive
towards
males they have seen win a fight.
Watching a fight gives fish a testosterone rush. The
same
happens to
football spectators: "Their hormone levels go all over the place
depending
on which way the match is going," says Peake.
Being watched probably also changes behaviour. The
benefits of
a hard-man
reputation might make witnessed fights more violent.
On the other hand, if neither contestant is sure of
winning,
they might
want to conduct their battles in private. This could explain why, in
song
thrushes and robins, the longest song duels are the quietest, says
Peake.
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