I need a way to objectively compare corvid nestling and fledgling gape coloration in the field as a potential measure of health. Are there examples of fields studies where flesh-tone color cards are matched or where a standard color card is used to calibrate lighting and color balance in a photograph? Or any other ways of objectively measuring color of a bird in hand in the field?
soil scientists use their Munsell color chart in the field, cartographers may consider the ITC color chart at their desk
hope it helps
This paper may have some useful guidance:
http://jesusmartinezpadilla.com/assets/2013.-jraptres.pdf
Thank you Hein, Daniel and John. These tips and references are very helpful!
Andria, If you can photograph the gapes in a controlled and standardized setting in the field, methods using photo-editing software (e.g., Adobe PhotoShop) seem promising. For example, see Kilner and Davies (1998, Nestling mouth colour: ecological correlates of a begging signal, Animal Behaviour, 56:705-712), Saino et al. (2003, Gape coloration reliably reflects immunocompetence of barn swallow (Hirundo rustica) nestlings. Behavioral Ecology 14:16-22), or Dugas and Dillow (2013, Rictal flanges of nestling birds are most colorful near the gape, Wilson Journal of Ornithology 125:430-433).
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