Nothing says romance like covering your face in white fluff and running like crazy through shrubbery.
That’s the courtship display North African birds called houbara bustards (Chlamydotis undulata) perform repeatedly. At the peak of the breeding season, males start at dusk, around 4 or 5 p.m., and keep going until about 9 the next morning, says Yves Hingrat of RENECO for Wildlife Preservation in Abu Dhabi, United Arab Emirates. When it’s showtime, feathers on their necks and heads rear up in a white froth. Whether or not a female is in sight, males run, sometimes round and round a bush. During befluffed sprinting, males breathe so loudly that a person 10 meters away can hear gasps.
The finale of the shrubbery rush can include calls pitched unusually low for a bird. When Hingrat worked at a captive breeding facility, staying late at his office meant “a concert of booms.”
“Sexually extravagant” is what Brian Preston of Liverpool John Moores University in England has called the species’ investment in courtship display. Males can live 23 years in captivity, so Preston and Hingrat wondered what toll such strenuous advertisement takes over time.
Male sperm quality peaks at about 4 years, with the next decade a slide downhill in sperm number and risk of malformation. And it turns out that sperm from older males retards chick growth, the researchers say February 3 in Nature Communications. The laggardly chicks may be poorer competitors and easier snacks for predators.
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The sperm decline is so steep that it may undermine display as an indication of quality. In animals, some theories suggest that a good show in courtship indicates a good dad (in the narrowest meaning of dad). Male bustards vary in how much of the year they devote to all-night fluffing, sprinting and booming. The more dedicated flirts as youngsters are still extreme in old age, sometimes extending their display season to more than five months. Despite heroic efforts at self-salesmanship, old birds’ sperm DNA has built up mutations. For female bustards, younger but less dedicated show-offs may be the better bets.
IT’S SHOWTIME During breeding season, a male bustard gives a seductive display of feather fluffing and dashing around, often ending with some quiet low-frequency sonic booms.
Credits: Video by C. Landsmann & M. Guillemin, Photo by Yves Hingrat