Song characteristics are age dependent in the willow warbler, Phylloscopustrochilus

Citation
D. Gil et al., Song characteristics are age dependent in the willow warbler, Phylloscopustrochilus, ANIM BEHAV, 62, 2001, pp. 689-694
Citations number
54
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Animal Sciences","Neurosciences & Behavoir
Journal title
ANIMAL BEHAVIOUR
ISSN journal
0003-3472 → ACNP
Volume
62
Year of publication
2001
Part
4
Pages
689 - 694
Database
ISI
SICI code
0003-3472(200110)62:<689:SCAADI>2.0.ZU;2-O
Abstract
Theory predicts that sexually selected characters should be condition depen dent if they are to be used as honest signals of male quality. One conseque nce of this dependence is that young and older males will differ in the exp ression of these characters. Many bird song characteristics, such as repert oire size or song length, are considered to have evolved through sexual sel ection. Consistent with this, several studies have shown that repertoire si ze increases with age. However, many of these studies used cross-sectional methods, comparing song characteristics in different age classes. This appr oach has the disadvantage that differential survival related to song can co nfound the data, emphasizing or hiding individual changes. To avoid this we combined a cross-sectional with a longitudinal analysis, where the same co hort is compared at different ages, to study how song characteristics chang e with age in the willow warbler. The longitudinal analysis showed that son g repertoire size (the set of different song elements) and element rate (nu mber of elements produced divided by song duration) increased between the f irst and second year. The cross-sectional analysis gave similar results, bu t there were no changes in element rate. From these results we can infer th at the development of several song characteristics is costly in this specie s. The different results provided by the two methods for element rate sugge st a negative correlation between element rate and the probability of survi val. The discrepancy between the methods implies that cross-sectional metho ds can provide erroneous conclusions in the study of changes with age in bi rd song. (C) 2001 The Association for the Study of Animal Behaviour.