Journal of Ornithology

, Volume 153, Issue 1, pp 1–22

Morphometric indices of body condition in birds: a review

Review

Abstract

Morphometric estimates of body condition are widely used by ornithologists, but which estimates work best is a matter of debate. We review morphometric approaches (body mass, ratio and residual condition indices, predictive regression models, fat scoring, and abdominal profiles) for estimating body condition (defined as fat mass) in birds. We describe the strengths and weaknesses of each approach. Across diverse indices and species (~200 estimates total), the mean r2 relating condition indices to mass of body fat was 0.55, and 64% of the r2 values were greater than 0.50. But despite their generally good performance, condition indices sometimes perform poorly (i.e., r2 is low). The data indicate that: (1) no single index was clearly best, (2) on average body mass alone, fat scores, and predictive multiple regression equations explained slightly more than 50% of the variation in fat content, (3) on average, ratio and residual indices explained slightly less than 50% of the variation in fat content, and (4) body mass alone, a variable that can be easily and reliably measured, is as good or nearly as good an indicator of fat content as any other condition index. We recommend that: (1) morphometric indicators of condition be empirically validated, (2) researchers publish their body composition data in sufficient detail that they can be used in future analyses exploring the relative merits of different condition indices, and (3) multiple regression directly on measured traits be used instead of condition indices whenever the condition index is not empirically validated.

Keywords

Body size Body composition Condition index Energy reserves Birds 

Zusammenfassung

Morphometrische Parameter zur Indikation der Körperkondition sind unter Ornithologen weit verbreitet, doch welche Parameter am Besten geeignet sind, wird lebhaft diskutiert. Wir stellen hier morphometrische Ansätze zur Indikation der Körperkondition, definiert als Fettmasse, bei Vögeln zusammen (Körpermasse, residuale Konditionsindices, Regressionsmodelle, Fettwert-Schätzungen und abdominales Pofil). Wir beschreiben die Stärken und Schwächen jedes dieser Ansätze. Über die verschiedenen Indices und Arten (insgesamt ~200 Ansätze) hinweg betrug das mittlere Bestimmtheitsmaß R2 zwischen Konditionsindices und Körpermasse 0,55, und 64% der R2-Werte waren größer als 0,50. Aber ungeachtet ihrer grundsätzlich ganz guten Bedeutung sind Konditionsindices manchmal sehr schwach (R2 ist gering). Die Daten deuten an, dass (1) kein Index für sich allein am besten war, (2) insgesamt Körpermasse, Fettwert und Regressionsmodelle etwas mehr als 50% der Variation im Fettgehalt erklärten, (3) im allgemeinen Verhältnisse und residuale Indices weniger als 50% der Variation im Fettgehalt erklärten, und (4) Körpermasse allein, eine leicht und zuverlässig zu bestimmende Größe, nahezu so gut ist als Indikator für den Fettgehalt wie jeder andere Konditionsindex. Wir empfehlen, dass (1) morphometrische Indikatoren der Körperkondition empirisch validiert werden, (2) Forscher ihre Daten zur Körperzusammensetzung so detailliert veröffentlichen, dass sie in zukünftigen Analysen verwendet werden können, um die relative Bedeutung der verschiedenen Konditionsindices überprüfen zu können, und (3) multiple Regressionsanalysen basierend auf den gemessenen Eigenschaften verwendet werden und nicht Konditionsindices, sofern diese nicht empirisch validiert sind.

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Copyright information

© Dt. Ornithologen-Gesellschaft e.V. 2011

Authors and Affiliations

  1. 1.Department of BiologyUniversity of NevadaRenoUSA
  2. 2.Department of Biochemistry and Cell BiologyRice UniversityHoustonUSA

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