Differential effects of endoparasitism on the expression of carotenoid- and melanin-based ornamental coloration

The striking diversity of sexual dimorphisms in nature begs the question: Why are there so many signal types? One possibility is that ornamental traits convey different sets of information about the quality of the sender to the receiver. The colourful, pigmented feathers of male birds seem to meet t...

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Bibliographic Details
Published in:Proceedings of the Royal Society. B, Biological sciences Biological sciences, 2000-08, Vol.267 (1452), p.1525-1531
Main Authors: McGraw, Kevin J., Hill, Geoffrey E.
Format: Article
Language:English
Subjects:
American Goldfinch
Animals
Body Mass Index
Carduelis Tristis
Carotenoids
Carotenoids - metabolism
Coccidia Honest Advertisement
Color
Colors
Eating
Host-Parasite Interactions
Infections
Isospora
Isospora - physiology
Isosporiasis - metabolism
Isosporiasis - physiopathology
Male
Male animals
Mating behavior
Melanin
Melanins - metabolism
Molting
Parasitism
Pigmentation
Plumage
Plumage Coloration
Songbirds - growth & development
Songbirds - metabolism
Songbirds - parasitology
Songbirds - physiology
USA
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Summary:The striking diversity of sexual dimorphisms in nature begs the question: Why are there so many signal types? One possibility is that ornamental traits convey different sets of information about the quality of the sender to the receiver. The colourful, pigmented feathers of male birds seem to meet the predictions of this hypothesis. Evidence suggests that carotenoid pigmentation reflects the nutritional condition of males during moult, whereas in many instances melanin pigmentation is a reliable indicator of social status. However, as of yet there have been no experimental tests to determine how these two ornament types respond to the same form of environmental stress. In this study, we tested the effect of endoparasitic infection by intestinal coccidians (Isospora sp.) on the expression of both carotenoid- and melanin-based ornamental coloration in captive male American goldfinches (Carduelis tristis). We found that the carotenoid-based plumage and bill coloration of parasitized males was less saturated than that developed by unparasitized males, but that the brightness and size of melanin-based black caps did not differ between the groups. These findings provide the most robust empirical support to date for the notion that carotenoid and melanin ornaments reveal different information to conspecifics.
ISSN:0962-8452
1471-2954
DOI:10.1098/rspb.2000.1174