Saks, L., McGraw, K. J. & Hõrak, P. (2003) How feather colour reflects its carotenoid content. Functional Ecology 17, 555–561.

Equation 2 (p. 557) in Saks et al. (2003) describing the calculation of chroma was erroneously presented. The value of chroma was calculated according to Endler (1990) and the correct presentation of this calculation should be as follows:

  • image(eqn 2)

where B = (Qb/Qt), G = (Qg/Qt), Y = (Qy/Qt), R = (Qr/Qt).

Unfortunately, the erroneous version of this equation has also been reprinted in Montgomerie (2006).


  1. Top of page
  2. References
  • Endler, J.A. (1990) On the measurement and classification of colour in studies of animal colour patterns. Biological Journal of the Linnean Society 41, 315352.
  • Montgomerie, R. (2006) Analyzing colors. Bird Coloration. Vol. I. Mechanisms and Measurements (eds G.E.Hill & K.J. McGraw), Table 3.2, p. 108. Harvard University Press, Cambridge, MA.