Recent research has added to a growing body of evidence that in promiscuous animals, including humans, the mechanism for successful reproduction is far more subtle than merely hoping for the best. The female of the specie may be picky about their sexual partner but the male may have the last say as the quality and quantity of sperm correlates strongly with how attractive the female mate is perceived to be.
This research was conducted on red junglefowl - an ancestor of the chicken - because female attractiveness is easy to measure and directly related to her fertility. Researchers found that the quantity and speed of the sperm produced by the male were strongly correlated to the attractiveness of the female. The mechanism that triggers this remains a mystery but the method by which the amount of sperm can be altered is known: males have two ejaculatory ducts that can fire independently so that attractive females get a shot from both barrels.
Is intriguing to speculate whether this mechanism is unleashed out of pure excitement or fear that the male is not going to get another chance!