Behavioral Aspects of Sperm Competition in Birds

The chapter discusses a review of sperm competition and behavioral adaptations to sperm competition in birds. Sperm competition is the competition between spermatozoa of different males to fertilize the eggs of a single female. The main emphasis in this chapter is on monogamy, extrapair copulations (EPCs), and associated behaviors, although sperm competition within other avian mating systems is also discussed. Four factors are known to influence the probability of extrapair paternity: (1) the timing and success of copulation— that is, sperm transfer by different males, (2) the relative numbers of copulations by different males, (3) the duration of sperm storage, and (4) sperm precedence. Extrapair paternity can be detected using genetic markers of two main types: those that are continuous variables (e.g., morphological characters) and those that are discontinuous variables (e.g., plumage color, enzyme polymorphisms). The chapter also discusses case studies on magpie (pica pica), common guillemot (utria aalge), swallow (Hirundo rustica), ringdove (Barbary dove, Streptopelia risoria), and indigo bunting (Passerina cyanea).