Testosterone and Avian Male Reproduction

在许多社会性一夫一妻制的鸟类中，雄性有时会进行额外的交配并产生可存活的后代。 传统观点认为，所有的雄性都一直在为这样的机会做好准备，但最近对生殖激素的实地研究表明，睾丸激素（T）在筑巢周期中波动很大，在求爱/交配期间早期达到峰值，然后伴随着戏剧性的行为转变而转向照顾活动（孵化和喂养雏鸟）。 有人提出，男性可能会经历减少的兴趣或能力的额外配对交配时，T是低的，他们可能会经历一个生理的“超时”阶段，他们的周期。 为了测试这一点，一个雄性家雀样本将被给予定时释放激素植入物（保持T水平高），而另一个样本作为正常（循环）对照。 由此产生的额外配对亲子关系模式，如DNA指纹所揭示的那样，将允许评估男性通过骑自行车所牺牲的东西。 相反，植入与对照雄性的雏鸟所接受的父母照顾的质量将显示从骑自行车中获得了什么。 平行实验将校准负责的机制。 这个项目将提高对促进和维持一夫一妻制的社会力量的理解，一夫一妻制是自然界中相对罕见的交配制度。 它集中注意力的成本和利益，男性投资大量在一个主要的育雏通过评估的因素，限制追求替代交配伙伴。

In many socially monogamous bird species, males sometimes engage in extra-pair copulations and sire viable offspring. Conventional wisdom has been that all males are continuously ready for such opportunities, but recent field studies of reproductive hormones have shown that testosterone (T) fluctuates greatly during the nesting cycle, peaking early during courtship/mating, then plummeting in tandem with a dramatic behavioral switch to care-giving activities (incubating and feeding nestlings). It has been proposed that males may experience reduced interest in or capacity for extra-pair matings when T is low, that they may then experience a physiological 'time-out' phase of their cycle. To test this, one sample of male house sparrows will be given time-release hormone implants (keeping T-levels high), while another sample serves as normal (cycling) controls. The resulting patterns of extra-pair paternity, as revealed by DNA fingerprinting, will allow assessment of what a male sacrifices by cycling. Conversely, the quality of parental care received by the nestlings of implanted vs. control males will show what is gained from cycling. Parallel experiments will calibrate the mechanism(s) responsible. This project will improve understanding of the social forces that promote and maintain monogamy, a relatively rare mating system in nature. It focuses attention on the costs and benefits available to males for investing heavily in one primary brood by evaluating the factors that constrain the pursuit of alternative mating partners.