Abstract
Eggshell pattern scoring, a method to quantify the degree of surface maculation, can potentially be a quick, inexpensive and reliable method to obtain information on eggshell appearance and spot patterns. The key pigment responsible for red-brownish hues, protoporphyrin IX, is often localized as spots, either on the surface or in distinct layers within the eggshell. Heritable pigment spotting has been linked to factors such as breeding performance and eggshell strength. In this study, we investigated whether pigment scoring of eggshell patterns is repeatable within and between observers, by testing observers under standardised conditions, using the eggshells of two commonly studied passerines, Great Tits (Parus major) and Blue Tits (Cyanistes caeruleus). We found that repeatability of eggshell scores was poor, both within and between observers for both the species. We, therefore, encourage future studies to use alternative methods for quantifying spot patterns, such as digital image analysis, a technique which has already been used extensively.
Zusammenfassung
Optische Kategorisierung von Eierschalenmustern besitzt nur geringe Wiederholpräzision
Die Kategorisierung von Eierschalenmustern, eine Methode zur Quantifizierung der Intensität der Oberflächenfleckung, kann eine schnelle, kostengünstige und zuverlässige Methode darstellen, um Informationen über Eierschalenerscheinung und Fleckenverteilung zu erlangen. Das Pigment, das hauptsächlich für die rot-braunen Farbtöne verantwortlich ist, das Protoporphyrin IX, kommt oft lokalisiert in Flecken entweder direkt an der Oberfläche oder in eng-begrenzten Schichten innerhalb der Eierschale vor. Erbliche, pigmentbedingte Fleckung ist mit Faktoren wie Bruterfolg und Schalenstärke in Verbindung gebracht worden. In der vorliegenden Studie untersuchen wir unter standardisierten Bedingungen am Beispiel der Eierschalen zweier beliebter Studienobjekte unter den Singvögeln, der Kohlmeise (Parus major) und der Blaumeise (Cyanistes caeruleus), inwiefern die optische Kategorisierung von Eierschalenmustern wiederholbar ist, sowohl durch ein und denselben Beobachter, als auch zwischen verschiedenen Beobachtern. Unsere Untersuchung zeigt für beide Meisenarten, dass die Wiederholbarkeit der Kategorisierung von Eierschalen beschränkt ist, sowohl im Vergleich wiederholter Kategorisierungen durch denselben Beobachter, als auch im Vergleich zwischen Beobachtern. Wir empfehlen daher in zukünftigen Untersuchungen alternative Methoden zur Quantifizierung von Fleckenmustern zu verwenden, zum Beispiel die digitale Bildanalyse, eine schon heute weit verbreitete Technik.
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Acknowledgments
This research was funded by the Natural Environment Research Council (NERC) through a studentship to K.B. The Worcestershire Wildlife Trust generously allowed the use of Chaddesley Woods National Nature Reserve. P.C. is an ARC Future Fellow (FT0991420). We are grateful to Franz Bairlein and two anonymous reviewers for comments that greatly improved the previous version.
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Communicated by F. Bairlein.
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Brulez, K., Choudhary, P.K., Maurer, G. et al. Visual scoring of eggshell patterns has poor repeatability. J Ornithol 155, 701–706 (2014). https://doi.org/10.1007/s10336-014-1053-9
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DOI: https://doi.org/10.1007/s10336-014-1053-9