Aggressive behavior of the male parent predicts brood sex ratio in a songbird
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Brood sex ratio is often affected by parental or environmental quality, presumably in an adaptive manner that is the sex that confers higher fitness benefits to the mother is overproduced. So far, studies on the role of parental quality have focused on parental morphology and attractiveness. However, another aspect, the partner’s behavioral characteristics, may also be expected to play a role in brood sex ratio adjustment. To test this hypothesis, we investigated whether the proportion of sons in the brood is predicted by the level of territorial aggression displayed by the father, in the collared flycatcher (Ficedula albicollis). The proportion of sons in the brood was higher in early broods and increased with paternal tarsus length. When controlling for breeding date and body size, we found a higher proportion of sons in the brood of less aggressive fathers. Male nestlings are more sensitive to the rearing environment, and the behavior of courting males may often be used by females to assess their future parental activity. Therefore, adjusting brood sex ratio to the level of male aggression could be adaptive. Our results indicate that the behavior of the partner could indeed be a significant determinant in brood sex ratio adjustment, which should not be overlooked in future studies.
KeywordsAttack latency Collared flycatcher Laying date Male quality Personality Sex allocation
We thank Rita Főző, Márton Herényi, Dorottya Kiss, Miklós Laczi, Gergely Nagy, and Sándor Zsebők for their help in the field and the lab and two anonymous referees for their valuable comments on the manuscript. We are also very grateful to the Pilis Park Forestry for its support.
The study was supported by grants from the Hungarian Scientific Research Found (grant no. F68295, PD75481, K75618, K101611), the Social Renewal Operational Programme of the Hungarian Government (TÁMOP 4.2.1./B-09/1-KMR-2010-0005 and 4.2.2./B-10/1-2010-0023), the Hungarian State PhD Scholarship to E. Szász, the Erdők a Közjóért Alapítvány, and the “Plan Nacional” program of the Spanish Government (ref. no. CGL2009-10652).
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