Carotenoid-based bill and eye ring coloration as honest signals of condition: an experimental test in the red-legged partridge (<Emphasis Type="Italic">Alectoris rufa</Emphasis>) |
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Authors: | Lorenzo Pérez-Rodríguez Javier Viñuela |
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Institution: | (1) Instituto de Investigación en Recursos Cinegéticos, IREC (CSIC, UCLM, JCCM), Ronda de Toledo, s/n, E-13005, Ciudad Real, Spain;(2) School of Biological Sciences, University of Aberdeen, Zoology Building, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK |
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Abstract: | Carotenoid pigments cannot be synthesized by vertebrates but must be ingested through the diet. As they seem to be a limited
resource, carotenoid-based ornaments are particularly interesting as possible honest signals of individual quality, in particular
of foraging efficiency and nutritional status. Some studies have demonstrated the condition dependence of carotenoid-based
plumage in birds. However, many other carotenoid-pigmented bare parts (i.e. skin, caruncles, bills, cere, and tarsi) are present
in birds but, in comparison with plumage, little is known about these traits as indicators of individual quality. Here, we
show that the eye ring pigmentation and bill redness of the red-legged partridge (Alectoris rufa) are positively associated to body condition and recent changes in body mass. Also, we found a negative relationship between
these two traits and heterophil-to-lymphocyte ratio, an indicator of physiological stress (the relationship with bill redness
being significant only for males). In an experiment, we found that after a period of reduction in food intake (with the consequent
loss of body mass), food-restricted birds showed lower eye ring pigmentation than ad-libitum-fed birds. Therefore, different
ornaments seem to reflect changes in body condition but at different speeds or intensities (eye ring, a fleshy ornament, appears
to respond more rapidly to changes in the nutritional status than a keratinized structure as the bill). These results indicate
that carotenoid-based ornaments are condition-dependent traits in the red-legged partridge, being therefore susceptible to
be employed as honest signals of quality in sexual selection. |
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Keywords: | Body condition Carotenoids Galliforms Honest signaling Ornaments Sexual selection |
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