AVIS-IBIS

Birds of Indian Subcontinent

Sexual size dimorphism and moult in the Plain Swift Apus unicolor

Publication Type:Journal Article
Year of Publication:2008
Authors:Garcia‐Del‐Rey, E, Gosler, AG, Gonzalez, J, Wink, M
Journal:Ringing & Migration
Volume:24
Issue:2
Date Published:2008
ISBN Number:0307-8698
Keywords:Apodidae, Apus, Apus apus, Apus unicolor
Abstract:The biometrics and moult of swifts are poorly known, yet represent important aspects of their breeding biology. In this study we investigated moult and used molecular sexing to characterise sexual size dimorphisms in the Plain Swift Apus unicolor. In contrast to previous work based on skin specimens, males were significantly larger than females with respect to wing length (2.0 mm difference) and tail length. The sexes did not differ in body mass. We derived a discriminant function by binary logistic regression to separate the sexes using wing, bill and tail length; the function was accurate in assigning 70% of the birds to their correct sex. Moult data obtained from 30 birds suggested that almost 25% of individuals overlapped breeding with the start of moult (estimate: 16 August ± 20 days) and that the progress of primary?feather moult was slow and initiated from at least two moult centres. Further studies are needed to investigate moult in relation to migratory strategy in this swift species.The biometrics and moult of swifts are poorly known, yet represent important aspects of their breeding biology. In this study we investigated moult and used molecular sexing to characterise sexual size dimorphisms in the Plain Swift Apus unicolor. In contrast to previous work based on skin specimens, males were significantly larger than females with respect to wing length (2.0 mm difference) and tail length. The sexes did not differ in body mass. We derived a discriminant function by binary logistic regression to separate the sexes using wing, bill and tail length; the function was accurate in assigning 70% of the birds to their correct sex. Moult data obtained from 30 birds suggested that almost 25% of individuals overlapped breeding with the start of moult (estimate: 16 August ± 20 days) and that the progress of primary?feather moult was slow and initiated from at least two moult centres. Further studies are needed to investigate moult in relation to migratory strategy in this swift species.
URL:http://dx.doi.org/10.1080/03078698.2008.9674379
Short Title:Ringing & Migration
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith