Female attractiveness affects paternal investment: experimental evidence for male differential allocation in blue tits

Katharina Mahr,Matteo Griggio,Herbert Hoi,Michela Granatiero

doi:10.1186/1742-9994-9-14

Katharina Mahr, Matteo Griggio + Show 2 more

Open Access

https://doi.org/10.1186/1742-9994-9-14

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Abstract

IntroductionThe differential allocation hypothesis (DAH) predicts that individuals should adjust their parental investment to their current mate’s quality. Although in principle the DAH holds for both sexes, male adjustment of parental investment has only been tested in a few experimental studies, revealing contradictory results. We conducted a field experiment to test whether male blue tits (Cyanistes caeruleus) allocate their parental effort in relation to female ornamentation (ultraviolet colouration of the crown), as predicted by the DAH.ResultsWe reduced the UV reflectance in a sample of females and compared parental care by their mates with that of males paired to sham-manipulated control females. As predicted by the DAH our results demonstrate that males paired with UV-reduced females invested less in feeding effort but did not defend the chicks less than males paired with control females.ConclusionsTo our knowledge, this is one of the first studies providing support for male differential allocation in response to female ornamentation.

Highlights

The differential allocation hypothesis (DAH) predicts that individuals should adjust their parental investment to their current mate’s quality
This corresponded to a slight enhancement of UV chroma of 1.76% in the control group, or an average reduction of 13.36% in the treatment group
Further analyses of this effect show a trend towards a negative correlation between laying-date and average prey item size in males paired to UV-reduced females (r = −0.42, n = 19, P = 0.07), which does not occur in the control group (r = 0.46, n = 10, P = 0.18)

Summary

Introduction

The differential allocation hypothesis (DAH) predicts that individuals should adjust their parental investment to their current mate’s quality. We conducted a field experiment to test whether male blue tits (Cyanistes caeruleus) allocate their parental effort in relation to female ornamentation (ultraviolet colouration of the crown), as predicted by the DAH. Females frequently choose males on the basis of traits [1] that may signal individual quality [2]. As a consequence they gain direct benefits, e.g. through highquality territories and paternal investment, or indirect benefits, because attractive mates may provide genes for passing viability and attractiveness to the offspring [2]. In species with biparental care males may gain benefits from choosing “high quality females” and adjust and as possible signals of female quality but very few have considered how they influence male parental investment [9,21,24,25]

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