08-19-2004, 03:11 AM #1Registered User
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Sexy males make bird mothers better
Sexy males make bird mothers better
00:01 18 August 04 NewScientist.com news service Female blue tits put in more parental effort if the father of their chicks is attractive, shows a new study.
Bringing up chicks is a risky business for many birds – the more effort the mother puts into feeding the youngsters, the less likely she is to survive to the next season. It is a risk that blue tit mothers would rather not take, unless, that is, they have a sexy dad.
The study by researchers at the Netherlands Institute of Ecology at the Centre for Terrestrial Ecology reveals that blue tit mothers not only put in less parenting effort when paired to a less attractive male, but their offspring grow up weaker. The results may shed light on how the sexes adjust their behaviour to attractiveness in many species.
“It’s the first time such behaviour adjustment has been shown,” says Tobias Limbourg, who led the research. “If a similar study was carried out on humans, I would assume that human mothers would show the same preferential treatment.”
Male blue tits deemed most attractive by females – and hence the ones with the most success at mating – are those with the brightest UV colouration on their crown feathers. However, this type of beauty is easily dulled, the Dutch researchers discovered.
Shortly before the paired birds’ chicks hatched, the team applied a sunscreen to the crown feathers of formerly attractive males, which blocked their UV colouration. The researchers then videotaped the birds’ behaviour when the chicks hatched, 10 days after and 14 days after their birth.
They found that the female blue tits paired to attractive males put much more effort into feeding and rearing their offspring. For example, they visited the nest more frequently with food for the chicks and brought more food to each chick in the nest, than those females paired to a male whose UV attractiveness had been reduced. The fathers’ feeding habits towards their offspring were unaffected.
By day 14, those chicks raised by the lazy mothers had stunted skeletons, correlating to reduced mating in the future and life expectancy compared to the chicks raised by hard working mothers.
“Our experiment shows that attractive individuals gain double benefit: first, through mate choice advantages; and second, because their mates show increased investment in their offspring,” Limbourg told New Scientist.
The mate choice advantage the mothers gain is that if they pair with a sexy male – this desirability is also likely to be inherited by his offspring.
Matthew Gage, a reproductive expert at the University of East Anglia, UK, says that the results are very interesting. “It goes to show what sort of sophisticated mechanisms have evolved for animals, even blue tits, to ensure that optimal parenting effort is saved for better mating in a future season.
“High UV colouration makes the birds more obvious to predators such as sparrow hawks and is therefore an ‘honest indicator’ of viability – if a feature makes a bird more likely to be predated, the fact that the animal has survived shows he is stronger, healthier and more resourceful,” explains Gage.
“It might also be a measure of the male’s foraging abilities, if he is able to find and eat the compounds necessary to produce his UV colouration.”
Journal reference: Proceedings of the Royal Society of London B (DOI: 10.1098/rspb.2004.2825)
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