Genes explain why some female zebra finches cheat

Promiscuous male zebra finches tend to sire promiscuous females

source: New Scientist vol 210 no 2817, June 18 2011 p21

Zebra finches are monogamous, and may have extra-marital affairs. Males with this tendency tend to sire promiscuous females, according to research by Wolfgang Forstmeier from Seewiesen's Max Planck Institute for Ornithology, Germany. He studied over 1,500 females over five generations. Promiscuous males were found to have more offspring. Their daughters inherited their promiscuous traits, despite this bringing no discernible advantages for females.