Song and immunological condition in male barn swallows {Hirundo rustica)

Behavioral Ecology (Impact Factor: 3.16). 01/1997; 8(4):364-371. DOI: 10.1093/beheco/8.4.364

ABSTRACT Male secondary sexual characters may have evolved as intra-or intersexual signals of male phenotypic or genetic quality. In birds, singing performance may have the function to honestly reveal .health and vigor of individual males. Infectious diseases and poor body conditions would therefore be expected to negatively influence singing performance. Since bird pathogens are known to elicit both a humoral and a cell-mediated immune response, it can be predicted that a negative relationship exists between singing performance and activity of the immune system. This prediction was tested for the first time in this correlational study. The relationships between song rate and features and hematological variables (concentration of leukocytes in peripheral blood, ratio of gamma-globulins to total plasma proteins, Mood cell sedimentation ratej • hematocrit) and body condition were analyzed in a population of barn swallows (Hirundo rustica). Song rate was negatively correlated with lymphocyte concentration and with the ratio of gamma-globulins to plasma proteins. Spectrographic analysis showed that features of song were not significantly correlated with hematological variables or body condition. The level of circulating testosterone was not correlated with song rate nor hematological variables. Thii study is the first to show a correlation between a bird's singing performance and hematological profile and suggests that song rate of male barn swallows may reflect their health status. Song in this species might thus have evolved because it allows prospecting females to assess aspects of phenotypic and/or genetic quality of potential mates. Ecol 8:364-371 (1997)]

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Available from: Anders Pape Moller, Feb 07, 2014
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    • "In their study, the immune challenge also led to a reduction of the body mass, forming a potential alternative pathway for the reduced duration of the rattle (Dreiss et al. 2008). Intriguingly, the song rate but not the rattle duration had previously been associated with parasitism (Møller 1991; Saino et al. 1997). Our pathway analysis provides support for a testosterone-regulated pathway , showing that it is the tick-mediated suppression of testosterone that causes a reduction in song consistency. "
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    ABSTRACT: Bird song is considered to have evolved via sexual selection and should as such honestly signal aspects of the quality of its bearer. To ensure honesty, the immunocompetence handicap hypothesis proposed a dual role of testosterone, having positive effects on sexual signalling but suppressive effects on immune function. However, recent studies showed that it is rather an immune activation that suppresses the androgen production. This reversed chain of causation may significantly alter the pathways, which translate the effects of parasites and pathogens into changes in the expression of male sexual traits. We infested male canaries with Ixodes ricinus tick nymphs to investigate the causal relationships between (ecto-)parasites, testosterone and sexual signalling, here singing behaviour. We focused on flexible song traits, which may quickly reflect changes in the infestation status, and tested whether these effects relate to changes in the plasma testosterone levels or health state. The experimental tick infestation altered the males’ song performance by reducing song consistency, a trait that had previously been identified to reflect male quality. The tick infestation lowered the plasma testosterone levels and had a negative effect on the health status in terms of a reduced hematocrit. Our pathway analysis then revealed that it is the parasite-induced reduction of the plasma testosterone levels but not of the health state that caused the changes in song consistency. Thus, our study supports the view that it is the effect of parasites and immune activation on plasma testosterone levels that generates the trade-off between immunocompetence and sexual signalling.
    Behavioral Ecology and Sociobiology 11/2013; 67(11):1-8. DOI:10.1007/s00265-013-1586-6 · 3.05 Impact Factor
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    • "Distinguishing between these aspects of individual condition is a crucial task for all studies testing hypotheses relating interindividual variation in life-history or ornamental traits to individual phenotypic quality. The latter holds especially for studies aiming to establish relationships between immune function and sexually selected traits (e.g., Dufva and Allander 1995; Saino et al. 1997; Møller 1998; Møller et al. 1998; Figuerola et al. 1999; Nunn et al. 2000) on the basis of simple hematological measures. The crucial point for interpreting such studies is the question of whether measured condition indices are reliable measures of individual performance. "
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    Canadian Journal of Zoology 02/2011; 80(4):636-643. DOI:10.1139/z02-038 · 1.35 Impact Factor
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    • "In birds, male song serves the dual function of mate attraction and territory defense (Catchpole and Slater 1995). Both song and singing interactions (Todt and Naguib 2000) may convey information about male quality (e.g., Otter et al. 1997), motivation (e.g., Vehrencamp et al. 2007), and condition (e.g., Saino et al. 1997) to both male and female receivers . Evidence that males sing at dawn for intrasexual communication comes not from observations of interactions between individuals but from observations of individual behaviors . "
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