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The use of tongue spots for aging and wing length for sexing Skylarks Alauda arvensis - A critical evaluation

Author:
  • Arne Hegemann
  • Rob Voesten
  • Kees van Eerde
  • Marco van der Velde
  • B Irene Tieleman
Publishing year: 2012
Language: English
Pages: 7-12
Publication/Series: Ringing & Migration
Volume: 27
Issue: 1
Document type: Journal article
Publisher: British Trust for Ornithology

Abstract english

The Skylark Alauda arvensis is a European passerine species lacking plumage dimorphism and having a complete post-nuptial moult in adults, and a complete post-juvenile moult in young birds. Tongue spots were thought to allow age discrimination after moult. Based on data from a study population in the Netherlands, where the age of many birds was known, we show that tongue spots are not useful for ageing Skylarks. Some nestlings lack tongue spots and half of all birds had tongue spots when three years or older. Regarding sex discrimination, males and females can usually be distinguished from a bimodal wing length distribution, but the threshold and amount of overlap in wing length between sexes vary greatly between studies. Here, we show that 98% of all individuals from our Dutch breeding population could be sexed correctly by wing length. However, during migration and winter, when populations from other regions co-occur in the same area, molecular analyses revealed that the overlap in wing length between sexes increased. Therefore, ringers need to be cautious when assigning sex, and small males especially are often misclassified. For example, based on criteria used in France, 14% of Dutch male Skylarks, which are partial migrants, would be misclassified as females.

Keywords

  • Biological Sciences

Other

Published
  • ISSN: 0307-8698