Sperm competition in birds and causes for its intra- and iterspecific variation

This bachelor thesis focuses on describing the occurrence and within- and between species variation of extra-pair paternity (EPP) in socially monogamous birds. In the first part of thesis I discribe variation in EPP levels among birds - I identify species with no EPP ever recorded, and species with extreme values of EPP. Extra-pair paternity seems to be more common in passerines than non-passerines. In the second part of my thesis, the most influential correlates of EPP levels in passerine birds are discussed. I summarize contemporary knowledge of the effect of these (mostly ecological) factors on EPP. These include breeding density and synchrony, population genetic diversity, adult mortality and longevity and male contribution to parental care. Key words: promiscuity, extar-pair paternity, extra-pair copulations, sperm competitio