Ptilochronology and fluctuating asymmetry in tail and wing feathers of Coal Tits Parus ater

Full article

Published:

Volume 46(2), December 1999. Pages 195-204.

Language:

English

Keywords:

fluctuating asymmetry, individual quality, natural selection, nutritional status, ptilochronology, wing and tail feathers.

Abstract:

Fluctuating asymmetry (FA) has been suggested as a valid index of individual quality, reflecting the physiological and nutritional state during the growth of a trait. For feathers aerodynamically functional in flight, theory predicts that deviations from bilateral symmetry in wing feathers should affect the flight more intensely than FA in tail feathers. FA should be lower in primaries than in rectrix feathers as a consequence of a possible more intense natural selection acting upon deviations from bilateral symmetry in the length of feathers in the wing than in the tail. This paper tests the above predictions working with the absolute FA in the length of Coal Tit´s Parus ater primaries and tail feathers. The results support the hypothesis of the association between the functional meaning of morphological traits and their measurable levels of FA, since, on average, population FA of wing feathers was half that observed for tail feathers. There was no association between FA and character size. The variance in FA was also higher in tail feathers than in wing feathers. Nevertheless, tail and wing FA in feather length were not significantly correlated, and feather growth rate, a measure of individual nutritional status, and FA in feather length were not associated for tail nor for wing feathers. These results do not support the prediction that FA is a valuable measurement of body condition and/or individual quality. A small meta-analysis with available data on FA and growth rate in birds showed that the relationship between these two traits is not significant and explains a low amount of variance (0.43%), which implies that there is no evidence for a general pattern in birds.