Blue Tit song repertoire size, male quality and interspecific competition

Abstract

A recent hypothesis suggested that bird song repertoire size is a reliable indication of male quality because the number of songs emitted by an individual and the expression of many traits important for fitness are highly dependent on developmental conditions. To test this hypothesis, we studied the relationship between song repertoire size and a trait known to be strongly affected by developmental conditions: tarsus length of Blue Tits Parus caeruleus. We studied this relationship in three populations presenting differences in density, quantity of food available and relative and absolute densities of Great Tits Parus major. Great Tit density may be an important factor because this species is supposed to be in competition for acoustic space with the Blue Tit. We found a positive correlation between Blue Tit dawn repertoire size and tarsus length in the three study populations which is consistent with the tested hypothesis. However, this correlation was only significant in the population with the lower Great Tit density. We discuss the significance of this variation and propose that interspecific competition may limit the action of sexual selection on song repertoire size.

Food-supplementing parents reduces their sons' song repertoire size

“…Song complexity is often positively correlated with survival and reproduction (e.g. Buchanan et al 1999;Doutrelant et al 2000), and thus generally reflects an adult male's quality. Being indelibly affected by early rearing conditions, song complexity ought to reflect intergenerational effects.…”

Song repertoire size correlates with measures of body size in Eurasian blackbirds

“…If larger body size is advantageous for male blackbirds on Helgoland, larger repertoires may signal higher male quality. In blue tits, Doutrelant et al (2000) found stronger positive correlations between tarsus length and repertoire size in two island populations than in one mainland population. The authors suggest that this was due to different levels of interspecific competition for acoustic space, as the relative great tit densities were lower on the island and blue tit repertoire sizes increased with decreasing great tit densities.…”

Effect of habitat quality on communication and signalling in the black-capped chickadee.

“…This in turn may lead to either inability to accurately produce speciesspecific songs or high variability in renditions of songs. This has already been demonstrated in other species in the Paridae such as in the great tits (Doutrelant et al 2000;Gorissen et al 2005), and also in other species outside of the Paridae (swamp sparrow Melospiza georgiana fNowicki et al 2002), zebra finch (Zann and Cash 2008) and European starling Sturn us vulgaris Spencer et al 2004)). Thus, in the black-capped chickadee, song consistency could provide reliable information about the ability of the signaller to effectively find and secure resources during the post-fledging period.…”