论文的标题是：Same-sex pair-bonds are equivalent to male-female bonds in a life-long socially monogamous songbird

Same-sex sexual behaviors are well documented in both captive and wild animals. In monogamous species, these behaviors areoften exclusive, each individual having only one same-sex partner. A bias in sex ratio has been proposed as a social contextyielding same-sex pair-bonding, but this hypothesis has rarely been tested. Focusing on a life-long pair-bonding songbird,the zebra finch Taeniopygia guttata, we tested whether same-sex pairing results from a shortage of individuals of the opposite sex. By experimentally skewingthe sex ratio towards members of one sex, we observed a greater proportion of same-sex pair-bonds of that sex. Moreover, weassessed whether the quality and stability of social interactions were equivalent in same-sex and malefemale pairs. Malemaleand femalefemale same-sex bonds display the same behavioral characteristics as malefemale ones: they are intense, highlyselective, and stable affinitive relationships involving the same behavioral displays already described in wild birds. Moreover,same-sex male bonds were sufficiently strong not to split up when individuals were given the opportunity to reproduce withfemales. Because the pair-bond in socially monogamous species represents a partnership that may give advantages for survival(e.g., resources defense, fighting against predators, etc.), we propose that same-sex pairing in the zebra finch may resultfrom the pressure to find a social partner.
作 者：Julie E. Elie, Nicolas Mathevon and Clmentine Vignal
期刊名称： Behavioral Ecology and Sociobiology
原文链接：http://www.springerlink.com/content/l211457604334146/ 
DOI： 10.1007/s00265-011-1228-9 
关键词： Animal homosexuality – Zebra finch – Same-sex sexual behavior – Sex ratio – Partnership – Pair-bond – Social network