Blue Grosbeak (Passerina caerulea) Science Article 3
For species in which females mate outside of the pair bond, selection should favor male mate-guarding behaviors that minimize investment in genetically unrelated offspring. Mate guarding may impose costs by diverting time and energy from activities such as foraging and seeking extra-pair copulations, so males should adjust their mateguarding behavior according to the risk of cuckoldry.
Laura K. Estep et al, Can. J. Zool. 83: 1143-1148 (2005)