据澳大利亚纽卡斯尔大学的生物学家在2007年时研究表示,在“一夫多妻“的鸟种中雄性鸟的居多,在“一夫一妻”的鸟种中雌性鸟“”居多。

生物科学家研究称地球上有130多种鸟类为,并且出现很多对长相厮守的同性鸟“夫妻”。

鸟类同性恋

Nearly one-fifth of all long-term greylag geese couples are gay, composed of two males. Credit: Dreamstime. 将近1/5的“夫妻”是女同性恋,图为两只mm。

(关于这种神奇鸟类的猛料,请看鸟类网magggot的文章:《灰雁的早孕/SM/同性恋/3P/NP行为》)

一些动物并非如人们料想的那样只有异性之间才能成功繁殖。最新研究显示,有一些特殊的鸟类可以在固定的周期内与同性和异性。通常,“同性恋”鸟类会向爱慕者发出精心准备的求爱“招术’,如果它们都互相爱慕就会相互碰触生殖器官,这也就表示新的一个同性家庭成立了。一些“同性恋”鸟类甚至会生幼崽,而且会相亲相爱的相守几年的幸福时光。

据科学家最近对93种野外鸟类研究发现,同性鸟通常会在外,它们的异性“伴侣”会负责抚养幼崽。据估计,在这93种鸟类中至少有5%的鸟类有着同性行为。科学家表示,这些鸟类的同性恋行为多和系统有着很大的关系。

科学家估计,在“一妻多夫”的鸟族中也许同样会存在雌性同性恋鸟,他们对此也会进行调查研究。

英文原文:从进化角度解释鸟类同性恋存在的合理性

Why It's OK for Birds to Be Gay

In greylag geese, nearly a fifth of all long-term couples are composed of two males. They're not alone: More than 130 bird species are known to engage in homosexual behavior at least occasionally, a fact that has puzzled scientists.

After all, in evolutionary terms same-sex mating seems to reduce the birds' chances of reproductive success. But that's not necessarily so, according to a new study. In a given species, the sex with lighter parental duties tends to mate more, period — whether with the same or the opposite sex.

Birds engage in all kinds of same-sex hanky panky, from elaborate courtship displays to mounting and genital contact to setting up house together. In some species the same-sex pairs even raise young (conceived with outside partners, obviously) and stay together for several years.

In 2007, a team led by Geoff MacFarlane, a biologist at the University of Newcastle in Australia, reported that male homosexual behavior was more common in polygynous bird species, where males mate with numerous females, and that female homosexual behavior was more common in monogamous species.

Intrigued, MacFarlane looked for help explaining the pattern in a theory predicting that whichever gender spends less time caring for young tends to have sex with more partners.

Scoring sex

To find out whether the theory might extend to homosexual behavior, MacFarlane and his team exhaustively combed the literature for accounts of same-sex courtship, mounting, or pair bonding. They focused on the 93 bird species whose homosexual interactions scientists had seen in the wild. For each species, the team calculated the frequency of homosexual behavior as well as both sexes' contributions to parenting.

Overall, homosexual behavior amounted to less than 5 percent of all sexual activity in the 93 species, though in some cases it was much higher. And sure enough, there was a strong correlation between a species' mating system and its homosexual behavior. Whichever sex did less parenting also typically did more same-sex canoodling – basically because they could. This tended to be true for the promiscuous males in polygynous species. The balance shifted to females in socially monogamous species, where the sexes split the work more equitably.

So far, female homosexuality hasn't turned up in the handful of birds where each female mates with many males, but MacFarlane's team predicts it may.

Evolutionary outcomes

The unburdened sex is free to take advantage of whatever mating opportunities come their way, MacFarlane explained. "Homosexual behavior is more likely to be maintained and not be selected against than if you are a sex that cares a lot for offspring and only has one or few reproductive partners," he said.

And with plenty of reproductive prospects, a little homosexual behavior won't have much effect on long-term reproductive success, MacFarlane said. "That's quite different to what the traditional argument is in the literature, where homosexual behavior is seen as a cost."

In some cases, homosexual alliances may even be adaptive, helping individuals defend territories, advance their social status, or get help with parental care.

MacFarlane's team is now investigating whether primates exhibit patterns like the one they've found in birds.

Their paper is being published in a forthcoming issue of the journal Animal Behavior.