Abstract

GONZALEZ-JARAMILLO, Mónica  and  CUEVA, Horacio de la. Influence of the outer rectrices asymmetry in flight efficiency of the Magnificent Frigatebird (Fregata magnificens). Huitzil [online]. 2012, vol.13, n.1, pp.6-16. ISSN 1870-7459.

The asymmetry of the outer rectrices in Fregata magnificens (Magnificent Frigatebird) has an influence on flight efficiency, while the deeply forked tail of this sexually dimorphic species plays a crucial role in its aerodynamic performance. In order to assess natural selection pressure on tail asymmetry, we modelled gliding flight performance of symmetric and asymmetric adult frigatebirds at the breeding colony of Isla Isabel, Mexico, through lift:drag ratio and glide polars and superpolars. We found significant differences between symmetric and asymmetric male and female frigatebirds when we analyzed gliding flight performance and flight compensation costs. Our theoretical model pointed that outer rectrices asymmetry has a greater effect on males than on females during gliding flight, and that flight efficiency of symmetric individuals will be higher than asymmetric ones, which will correct asymmetry according to flight velocity by adding drag costs. Further research in survival rates of tail symmetric and asymmetric males, nest construction costs, and breeding success could reveal the advantages of having a symmetric tail in this species and elucidate if asymmetry has a fitness cost.

Keywords : tail asymmetry; seabird; flight performance; natural selection.

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