canberrabirds

Bush-league male mates stress out female finches

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Subject: Bush-league male mates stress out female finches
From: "Tony Lawson" <>
Date: Tue, 8 Feb 2011 08:16:58 +1100
By Katherine Harmon | Feb 1, 2011 08:01 PM | 0

Whether they are finding love in a flock or a lab, female Gouldian finches (Erythrura gouldiae) know what they're looking for: a fit male with head feathers that match their own. And the females that don't end up with a desirable mate are slower to lay eggs and wind up more physiologically stressed, according to new research.
Animal species that bond in monogamous pairs-whether for life or just for a 
season-are often assumed to have found a perfectly satisfactory mate for 
their tastes. But, such a presumption is likely "naive," contend researchers 
behind the new finch work. "This logic would be akin to assuming that only 
women as attractive as Angelina Jolie find a man such as Brad Pitt 
attractive," they noted in their paper published online February 1 in 
Proceedings of the Royal Society B: Biological Sciences. So just as it is in 
the human world that "only one high-quality woman is able to socially pair 
with Brad Pitt" (at least as of late), pair-bonded animals also likely often 
have to settle for a less-than-ideal mate, the researchers point out in the 
study.
As a species that usually lives for less than three years and-breeds only 
once or twice a year-female Gouldian finches have a keen interest in picking 
the best mate each season. To do this, they rely in large part on the 
shorthand signal of a colorful male's head feathers (which are either red or 
black) to indicate the likely fitness of their prospective offspring. 
Offspring from mixed pairs have a 40 to 80 percent higher mortality rate, so 
males with a matching head color are most attractive. In the wild, these two 
color types often coexist in uneven numbers, leaving some females to "face 
the choice of breeding with an incompatible partner or not breeding at all," 
the researchers, led by Simon Griffith, of Macquarie University's biology 
department, noted in their study.
To assess the impact of this decision, Griffith and his team set out to try 
to measure "the extent of female 'satisfaction' with her social partner." To 
do this, they monitored several waves of pairing couples in a large aviary 
(with 20 to 28 birds per group) and in 100 more pairings in controlled 
single-pair lab cages. In both situations, females who ended up with a mate 
with a different head color were slower to lay eggs (by 20 days to a month) 
and had three- to four-times higher levels of the animal stress hormone 
corticosterone. And especially for females in the forced-pair cage 
experiments, the stress of being faced with an unattractive mate set in 
quickly, leading to "significantly higher conticosterone" within 12 hours of 
pairing. The speed of this stress response, the researchers suggest, "was 
not driven by indirect effects of male behavior on the female, but rather by 
her initial perception of him."
The similarity of response in an open-selection aviary versus a pre-selected 
single-pair cage (where females were each paired once with a compatible and 
incompatible male) suggests that the female's reaction has less to do with 
her option to choose than with the mate she ends up with.
So although the birds might not be consciously weighing their options and 
rationalizing their decision (or lot), the researchers suggest the finches 
were revealing some level of "internal conflict," they note. "These females 
are making the best of a bad situation and are dissatisfied with their 
partner although he does represent a better option than not breeding at 
all."
But these vexed female finches are not given entirely to avifaunal despair. 
In fact, the authors posit, the physiological stress response might be a way 
of prompting them to other adaptive behaviors, such as investing less in 
that season's offspring or looking for love outside of the nest.
http://www.scientificamerican.com/blog/post.cfm?id=bush-league-male-mates-stress-out-f-2011-02-01&WT.mc_id=SA_CAT_EVO_20110207


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