Journal of Ornithology

, Volume 153, Issue 4, pp 1053–1065 | Cite as

Quantifying the effect of feather abrasion on wing and tail lengths measurements

Original Article


Wing and tail length measurements are important tools in ornithology. Amongst linear measurements, wing length has been considered to be the best indicator for body size for taxonomy and ecomorphology, as well as for studies about the impact of climate change on morphology. As feathers are dead tissue, abrasion will lead to a reduction in wing and tail length within a moult cycle. The aim of our study was to analyse the effect of feather abrasion on wing and tail length in the Stonechat Saxicola torquata. Generalized additive models revealed that wing lengths and tail lengths decrease significantly between the termination of feather growth and the next moult. The decrease in wing length was faster with increasing feather age. The decrease in tail length was nearly linear through time. Multiple measurements of recaptured individuals revealed a similar decrease in wing length to that observed in analyses based on single measurements of multiple individuals. An analysis of the length of the third outermost primary revealed the same pattern. Hence, the decrease in wing and tail length over time was caused by within-bird changes and not by mortality, emigration or immigration associated with wing and tail length. We found that feather abrasion was more pronounced in females compared to males at least during the breeding season, but there were no strong indications that feather abrasion was more pronounced in birds before their first complete moult compared to older individuals. A review of previous studies showed that a reduction in wing length of about 0.2–0.5 %/month is a common phenomenon. Our study shows that feather abrasion must be taken into account when analysing time-series of wing and tail length measurements to avoid spurious conclusions.


Stonechat (Saxicola torquataWing length Tail length Feather abrasion Moult Morphology 


Quantifizierung des Effekts der Federabnutzung auf Flügel- und Schwanzlängenmessungen

Flügel- und Steuerlänge sind wichtige Maße in der Ornithologie, wobei die Flügellänge oft als Indikator für die Körpergröße angesehen wird. Dies gilt sowohl für taxonomische und ökomorphologische Untersuchungen wie auch für Studien, die den Einfluss des Klimawandels auf die Morphologie von Vögeln zum Thema haben. Da Federn jedoch aus totem Gewebe bestehen, führen Umwelteinflüsse zur permanenten Abnutzung und damit zur Verkürzung der Flügel- und Steuerlängen zwischen zwei Mauserphasen. In dieser Arbeit analysierten wir die Auswirkungen der Federabnutzung auf die Flügel- und Steuerlängen beim Schwarzkehlchen Saxicola torquata. Generalisierte additive Modelle zeigten, dass die Flügel- und Steuerlängen signifikant mit zunehmendem Alter der Federn abnehmen. Die Abnahme der Flügellänge, wie auch die Länge der dritten äußeren Handschwinge, beschleunigte sich dabei mit fortschreitendem Federalter. Die Abnahme der Steuerlänge erfolgte dagegen nahezu linear. Die alleinige Berücksichtigung von Erstfängen mit unterschiedlichem Federalter ergab ein ähnliches Ergebnis wie die Analyse der individuellen Variation der Flügel- und Federlängen von Wiederfängen. Dies weist darauf hin, dass die Abnahme der durchschnittlichen Flügel- und Steuerlängen mit zunehmendem Abstand zur letzten Mauser innerhalb der Population nicht durch morphologieabhängige Sterblichkeit, Emigration oder Immigration bedingt war, sondern durch die individuelle Abnutzung der Federn. Bei den Weibchen nutzten sich die Federn zumindest während der Brutzeit stärker ab als bei den Männchen. Wir fanden aber keine eindeutigen Hinweise darauf, dass sich beim Schwarzkehlchen die Federn vor der ersten Vollmauser stärker abnutzten als die Federn nach der ersten Vollmauser. Ein Vergleich mit früheren Studien zeigte, dass eine Abnahme der Flügellängen um 0,2 % bis 0,5 %/Monat zwischen zwei Mauserzyklen ein verbreitetes Phänomen ist. Die Verkürzung der Flügel- und Steuerlänge mit zunehmendem Federalter sollte daher bei Untersuchungen, denen Daten aus einem längeren Zeitraum zugrunde liegen, berücksichtigt werden, um fehlerhafte Schlussfolgerungen zu vermeiden.



We thank W. Hochachka for statistical advice and for the discussion of the manuscript and J. Korb and P. Atkinson for their kind help with the literature search. We are grateful to an anonymous reviewer for valuable comments on earlier drafts of this manuscript. The Institute of Avian Research “Vogelwarte Helgoland” provided H.F. with “Helgoland”-rings. R. Schlenker and K.-H. Siebenrock, Max-Planck-Institute for Ornithology, Radolfzell, provided H.F. with some trapping equipment. The farmers of the Düffel and the Heubach-Lowland generously allowed working on their estates. The data analysis for this project was supported by a grant from the Deutsche Ornithologen-Gesellschaft (DO-G).


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Copyright information

© Dt. Ornithologen-Gesellschaft e.V. 2012

Authors and Affiliations

  1. 1.BorkenGermany
  2. 2.Behavioural BiologyUniversität OsnabrückOsnabrückGermany

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