Much attention has recently been focused on the factors determining mating success in animals. Most emphasis has been on variation in male characteristics, as females are often assumed to be the choosier sex. However, in monogamous species, securing a mate with high reproductive potential is important to both sexes. Here we show by means of manipulation experiments that male zebra finches selectively pair with females that, because of previous exposure to a high quality diet, will lay large clutches. This is the first demonstration that a female's probability of obtaining a mate is directly linked to her egg production capacity independent of her age, experience or body size.