The idle ramblings of a Jack of some trades, Master of none

What attribute in a male attracts a female? Among humans, there are as many answers as you might hanker for. If you believe Marilyn Monroe2, a bit of a pot is a turn-on. Well, as long as the owner of the pot is nervous and shy and perspiring a little, and gentle, kind and worried. Among animals, there is usually one quality, a preponderance of which in a male ensures that he gets all the ladies he wants. This might be a gorgeous plumage3, a bigger build4, fancier DIY ability5, or particularly proficient skills of musical composition6.

Evolutionary biologists have listed variations in female preference for male traits as a powerful driver for speciation. In other words, if in a species, some females prefer a large beak in a male, and others prefer a brilliant plumage, then it is likely that over time, the population will split into two groups. Eventually, these subspecies will be unable to interbreed and they will become new species.

A similar dynamic seems to be happening among two populations of yellowthroat warblers. The distinctive characteristic of these birds is a bright yellow chest (a bib) and dark black facial pigmentation (a mask). In New York, female yellowthroats appear to favour males with brighter bibs. This makes sense: the pigmentation is caused by carotenoids, an antioxidant group of molecules, indicating robust health. In Wisconsin, though, the females prefer darker masks. Since Zorro has not been known to have been a bird, and because melanin, the molecule causing black colouring is not correlated with good health, this finding is somewhat puzzling.

Indeed, when populations of the birds are mixed and the females are monitored to see how long they gawk at particular males, the denizens of the Empire State continue to prefer the yellower males, and the Wisconsinites are turned on by the blacker masks. Perhaps, in Wisconsin, masks are better indicators of health than the bibs.

There have been several periods in human history where vivid colours worn by men tended to attract women. Of course, it also helped if the guy didn't have bad breath and looked like he could carry his gal off into a cave and ravish her politely. According to Plum, all the diffident guy needed to do was to grab the girl, look deeply into her eyes and breathe, "My woman." Birds, it appears, are far more sophisticated.


1. Matt Kaplan: Female Fickleness May Split A Species, ScienceNow Daily News, 30 Nov 2007

2. Billy Wilder: The Seven Year Itch, starring Marilyn Monroe. 1955

3. Geoffrey Hill: A Red Bird in a Brown Bag - The Function and Evolution of Colourful Plumage in House Finch, Oxford University Press, 2002.

4. MacLaren, R. D., et al: Female Preferences for Sailfin and Body Size in the Sailfin Molly, Poecilia latipinna. Ethology 110 (5), 363-379. (2004)

5. Solera J. J., et al: Intra- and interspecific relationships between nest size and immunity. Behavioral Ecology, 18: 781-791. (2007)

6. Vaneechoutte, M.; Bird song as a possible cultural mechanism for speciation. Journal of Memetics - Evolutionary Models of Information Transmission, 1. (1997)


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