Health, parasitism, plumage color and song in Cherrie's tanager, Ramphocelus costaricensis

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)

First Committee Member

William Searcy - Committee Chair


Display traits such as avian song and plumage color have been predicted to reveal to potential mates the quality of the signaler in terms of health and resistance to parasites. Furthermore, it has been proposed that display traits and parasite resistance are especially closely related in tropical regions where parasitism may be more prevalent and its effects on host health more intense. In this study, parasitism, health, and their relationship to each other and to song and plumage color were investigated in a natural population of Cherrie's tanager (Ramphocelus costaricensis ), a tropical resident songbird. Mean hematological values did not differ greatly from those in Nearctic resident and Neotropical migrant passerines, and differences between developmental stages, sexes, years and seasons were similar to those observed in temperate passerines. At least nineteen species of parasites were found in the study population. Parasite load tended to be higher in adults than in younger birds and higher in males than in females. A cestode (Raillietina sp.) and a hematozoan (Haemoproteus thraupi) had a large negative interactive effect on hemoglobin concentration, and there was evidence for negative interactive effects on total plasma protein concentration and total body mass as well. The results of this study suggest that, although the pathological effects of a single parasite taxon may be small or difficult to detect, the combined effects of multiple parasites may have important health consequences in free-living host populations. Cestode infestation during molt showed a strong negative relationship to the brightness and chroma of the male scarlet plumage patch measured after molt was completed. Condition was positively related to song performance time, plumage brightness, and plumage chroma, and negatively related to intestinal parasitism and chewing lice intensity. The effects of intestinal parasitism on condition appeared to persist over seasons. Plumage color tended to signal parasitism over a longer time period than song performance time, which was more sensitive to immediate condition. Song performance time was negatively related to chewing lice intensity and positively related to intestinal parasitism. Both types of signals could provide useful information about male parasitism and condition to females.**This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Windows 95 or higher.


Biology, Ecology

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