Sexual selection in the collared flycatcher (Ficedula albicollis) : A life-history perspective

Sammanfattning: This thesis integrates sexual selection theory with life history theory to elucidate the causes and consequences of variation in a male secondary sexual trait. The model organism, the collared flycatcher (Ficedula albicollis), was studied on Gotland, Sweden.Male collared flycatchers possess a conspicuous white forehead patch that was shown to function as an honest signal of fighting ability in contests over nest sites (a necessary resource to attract females), where males with relatively large patch size enjoyed a competitive advantage. Forehead patch size wasfound to be a heritable condition-dependent trait affected by a male's natal environment and by genotype-environment interactions, As revealed by experimental manipulations males traded their investment of resources in competition over mates (indicated by patch size) against their investment in parental care and vice versa.Although forehead patch size could not be used as a cue of male parental ability by mate-choosing females, there was a positive relationship between male patch size and female fecundity but only among late breeding birds. This probably was a result of quality differences between territories becoming moreimportant as general rearing conditions declined over the season.Average life span was highest among males with intermediate forehead patch size suggesting that large-patched males sacrificed not only their parental ability but also their own future survival chances for a current mating advantage.Consequently, my results suggest that both sexual selection theory and life history theory would benefit from an increased integration.