Journal of Ornithology

, Volume 155, Issue 3, pp 701–706 | Cite as

Visual scoring of eggshell patterns has poor repeatability

  • Kaat BrulezEmail author
  • Pankaj K. Choudhary
  • Golo Maurer
  • Steven J. Portugal
  • Rebecca L. Boulton
  • Simone L. Webber
  • Phillip Cassey
Original Article


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.


Pigmentation Protoporphyrin Repeatability Spot scoring Tits 


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.



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.

Supplementary material

10336_2014_1053_MOESM1_ESM.docx (72 kb)
Supplementary material 1 (DOCX 67 kb)


  1. Baird T, Solomon SE, Tedstone DR (1975) Localisation and characterisation of egg shell porphyrins in several avian species. Br Poult Sci 16(2):201–208. doi: 10.1080/00071667508416177 PubMedCrossRefGoogle Scholar
  2. Bland JM, Altman DG (1999) Measuring agreement in method comparison studies. Stat Methods Med Res 8(2):135–160PubMedCrossRefGoogle Scholar
  3. Brulez K, Cassey P, Meeson A, Mikšík I, Webber SL, Gosler AG, Reynolds SJ (2014) Eggshell spot scoring methods cannot be used as a reliable proxy to determine pigment quantity? J Avian Biol 45(1): 94–102. doi: 10.1111/j.1600-048X.2013.00236.x CrossRefGoogle Scholar
  4. Bulla M, Šálek M, Gosler AG (2012) Eggshell spotting does not predict male incubation but marks thinner areas of a shorebird’s shells. Auk 129(1):26–35. doi: 10.1525/auk.2012.11090 CrossRefGoogle Scholar
  5. Cassey P, Portugal SJ, Maurer G, Ewen JG, Boulton RL, Hauber ME, Blackburn TM (2010) Variability in avian eggshell colour: a comparative study of museum eggshells. PLoS ONE 5(8):e12054. doi: 10.1371/journal.pone.0012054 PubMedCentralPubMedCrossRefGoogle Scholar
  6. Cassey P, Thomas GH, Portugal SJ, Maurer G, Hauber ME, Grim T, Lovell PG, Mikšík I (2012) Why are birds’ eggs colourful? Eggshell pigments co-vary with life-history and nesting ecology among British breeding non-passerine birds. Biol J Linn Soc 106(3):657–672. doi: 10.1111/j.1095-8312.2012.01877.x CrossRefGoogle Scholar
  7. Cherry MI, Gosler AG (2010) Avian eggshell coloration: new perspectives on adaptive explanations. Biol J Linn Soc 100(4):753–762. doi: 10.1111/j.1095-8312.2010.01457.x CrossRefGoogle Scholar
  8. Choudhary PK (2008) A tolerance interval approach for assessment of agreement in method comparison studies with repeated measurements. J Stat Plan Infer 138(4):1102–1115CrossRefGoogle Scholar
  9. De Coster G, De Neve L, Lens L (2012) Intraclutch variation in avian eggshell pigmentation: the anaemia hypothesis. Oecologia 170(2):297–304. doi: 10.1007/s00442-012-2304-1 PubMedCrossRefGoogle Scholar
  10. De Coster G, De Neve L, Lens L (2013) Intra-clutch variation in avian eggshell pigmentation covaries with female quality. J Ornithol. doi: 10.1007/s10336-013-0974-z Google Scholar
  11. de la Fuente de Val G, Atauri JA, de Lucio JV (2006) Relationship between landscape visual attributes and spatial pattern indices: a test study in Mediterranean-climate landscapes. Landsc Urban Plan 77(4):393–407CrossRefGoogle Scholar
  12. Demidenko E (2004) Mixed models: theory and applications. Wiley, New YorkCrossRefGoogle Scholar
  13. Gorchein A, Lim CK, Cassey P (2009) Extraction and analysis of colourful eggshell pigments using HPLC and HPLC/electrospray ionization tandem mass spectrometry. Biomed Chromatogr 23(6):602–606. doi: 10.1002/bmc.1158 PubMedCrossRefGoogle Scholar
  14. Gosler AG, Barnett PR, Reynolds SJ (2000) Inheritance and variation in eggshell patterning in the great tit Parus major. Proc R Soc Lond B 267(1461):2469–2473. doi: 10.1098/rspb.2000.1307 CrossRefGoogle Scholar
  15. Gosler AG, Higham JP, Reynolds SJ (2005) Why are birds’ eggs speckled? Ecol Lett 8(10):1105–1113. doi: 10.1111/j.1461-0248.2005.00816.x CrossRefGoogle Scholar
  16. Gosler AG, Connor OR, Bonser RHC (2011) Protoporphyrin and eggshell strength: preliminary findings from a passerine bird. Avian Biol Res 4(4):214–223. doi: 10.3184/175815511X13207833399666 CrossRefGoogle Scholar
  17. Herring W, Miller D, Bertrand J, Benyshek L (1994) Evaluation of machine, technician, and interpreter effects on ultrasonic measures of backfat and longissimus muscle area in beef cattle. J Anim Sci 72(9):2216–2226PubMedGoogle Scholar
  18. Holveck M-J, Grégoire A, Staszewski V, Guerreiro R, Perret P, Boulinier T, Doutrelant C (2012) Eggshell spottiness reflects maternally transferred antibodies in blue tits. PLoS ONE 7(11):e50389PubMedCentralPubMedCrossRefGoogle Scholar
  19. Igic B, Hauber ME, Galbraith JA, Grim T, Dearborn DC, Brennan PL, Moskát C, Choudhary PK, Cassey P (2010) Comparison of micrometer-and scanning electron microscope-based measurements of avian eggshell thickness. J Field Ornithol 81(4):402–410CrossRefGoogle Scholar
  20. Kennedy GY, Vevers HG (1973) Eggshell pigments of the araucano fowl. Comp Biochem Physiol B 44(1):11–25PubMedGoogle Scholar
  21. Kennedy GY, Vevers HG (1976) Survey of avian eggshell pigments. Comp Biochem Physiol B 55(1):117–123. doi: 10.1016/0305-0491(76)90183-8 PubMedGoogle Scholar
  22. Kersten D, Yuille A (2003) Bayesian models of object perception. Curr Opin Neurobiol 13(2):150–158PubMedCrossRefGoogle Scholar
  23. Kersten D, Mamassian P, Yuille A (2004) Object perception as Bayesian inference. Annu Rev Psychol 55:271–304PubMedCrossRefGoogle Scholar
  24. Kilner RM (2006) The evolution of egg colour and patterning in birds. Biol Rev 81(3):383–406. doi: 10.1017/S1464793106007044 PubMedCrossRefGoogle Scholar
  25. Lin LI (2000) Total deviation index for measuring individual agreement with applications in laboratory performance and bioequivalence. Stat Med 19(2):255–270PubMedCrossRefGoogle Scholar
  26. López de Hierro M, De Neve L (2010) Pigment limitation and female reproductive characteristics influence egg shell spottiness and ground colour variation in the house sparrow (Passer domesticus). J Ornithol 151(4):833–840CrossRefGoogle Scholar
  27. Mägi M, Mänd R, Konovalov A, Tilgar V, Reynolds S (2012) Testing the structural-function hypothesis of eggshell maculation in the Great Tit: an experimental approach. J Ornithol 153:645–652. doi: 10.1007/s10336-011-0782-2 CrossRefGoogle Scholar
  28. Maurer G, Portugal SJ, Cassey P (2011) Review: an embryo’s eye view of avian eggshell pigmentation. J Avian Biol 42(6):494–504. doi: 10.1111/j.1600-048X.2011.05368.x CrossRefGoogle Scholar
  29. Reynolds SJ, Martin GR, Cassey P (2009) Is sexual selection blurring the functional significance of eggshell coloration hypotheses? Anim Behav 78(1):209–215. doi: 10.1016/j.anbehav.2009.03.003 CrossRefGoogle Scholar
  30. Sanz JJ, García-Navas V (2009) Eggshell pigmentation pattern in relation to breeding performance of Blue tits Cyanistes caeruleus. J Anim Ecol 78(1):31–41. doi: 10.1111/j.1365-2656.2008.01465.x PubMedCrossRefGoogle Scholar
  31. Stoddard MC, Stevens M (2010) Pattern mimicry of host eggs by the common cuckoo, as seen through a bird’s eye. Proc R Soc Lond B 277(1686):1387–1393. doi: 10.1098/rspb.2009.2018 CrossRefGoogle Scholar
  32. Underwood TJ, Sealy SG (2002) Adaptive significance of egg colouration. Avian incubation, behaviour, environment and evolution. Oxford University Press, OxfordGoogle Scholar
  33. Wells RG (1968) The measurement of certain egg quality characteristics: a review. In: Carter TC (ed) Egg quality: a study of the hen’s egg. Oliver & Boyd, EdinburghGoogle Scholar
  34. Yezerinac SM, Lougheed SC, Handford P (1992) Measurement error and morphometric studies: statistical power and observer experience. Syst Biol 41(4):471–482. doi: 10.2307/2992588 CrossRefGoogle Scholar

Copyright information

© Dt. Ornithologen-Gesellschaft e.V. 2014

Authors and Affiliations

  • Kaat Brulez
    • 1
    Email author
  • Pankaj K. Choudhary
    • 2
  • Golo Maurer
    • 1
    • 3
  • Steven J. Portugal
    • 1
    • 4
  • Rebecca L. Boulton
    • 1
    • 3
  • Simone L. Webber
    • 1
    • 5
  • Phillip Cassey
    • 1
    • 3
  1. 1.Centre for Ornithology, School of BiosciencesUniversity of BirminghamBirminghamUK
  2. 2.Department of Mathematical SciencesUniversity of Texas at DallasRichardsonUSA
  3. 3.School of Earth and Environmental SciencesUniversity of AdelaideAdelaideAustralia
  4. 4.Structure and Motion Lab, Royal Veterinary CollegeUniversity of LondonHatfieldUK
  5. 5.NHBS Ltd.DevonUK

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