Table 2 Commonly used proxies for quality to evaluate the relationship between carotenoid-based feather coloration and individual quality

From: Carotenoid metabolism strengthens the link between feather coloration and individual quality

Category Metric Relationship with quality
Condition Body mass +
  Size-adjusted body mass +
  Ptilochronology +
Immune and oxidative physiology Anti-oxidant capacity +
  Antibody count +
  Disease survival +
  Environmental pollutant
  HL ratio
  Pathogen challenge
  Oxidative damage
  PHA response +
  WBC count +
Parasite Load
  Resistance +
Parental and reproductive quality Clutch size +
  Feeding rate +
  Fledgling number +
  Fledgling success +
  Lay date
  Nest attentiveness +
  1. + indicates that this measure has a positive correlation with individual quality.− indicates that this measure has a negative correlation with individual quality