BIRDS have more sophisticated sex lives than we thought. For the first time, some birds have been shown to use smell to identify their partners. And others are likely to dump their mates for being bad parents.
Birds are thought to identify each other by sight and sound. But Francesco Bonadonna at the National Centre for Scientific Research in Montpellier, France, and his colleagues have found that a small Antarctic seabird called a prion (Pachyptila desolata), locates its partner using smell. The researchers presented 20 birds with a choice of scent-laced cotton bags giving off the strong musky odour of either their mate or a stranger, and found that 17 approached the bags smelling of their partner (Science, vol 306, p 29).
The nocturnal prions, which mate for life and live in burrows, are thought to use smell to identify their partners in the gloom without having to make noises that may attract predators. 鈥淢ammals can identify individuals by smell, but this is the first instance where birds can do it, too,鈥� says Bonadonna.
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Another monogamous seabird, the common murre (Uria aalge), will 鈥渄ivorce鈥� a partner for being a bad parent. Biologists have struggled to explain why some birds change partners after a poor reproductive season, but Allison Moody at Memorial University of Newfoundland in St John鈥檚, Canada, and her colleagues have found that murres tend to dump partners that either fed chicks poorly or killed them by being inept parents. For instance, one male murre in a colony in Newfoundland accidentally kicked his chick off a cliff during a skirmish with a neighbour, while another had a tendency to stand beside its egg rather than incubate it. Both got the boot.
But partners will only initiate a divorce when a better mate becomes available (Behavioral Ecology and Sociobiology, DOI: 10.1007/s00265-004-0856-8). 鈥淭hese birds are sitting shoulder to shoulder all day and watching who brings the fish in. They always re-pair with a better partner,鈥� says team member Anne Storey.
Ornithologist Andre Dhondt at Cornell University in New York says both studies highlight the importance of individual recognition in birds that mate monogamously. 鈥淵ou need to know your mate, but also which others are available and how good they are. And if you can鈥檛 do it by sight or sound, it must be smell.鈥�
鈥淢urres tend to dump partners that either fed chicks poorly or killed them by being inept鈥�