Katherine Louise Buchanan

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In a wide range of bird species, females have been shown to express active preferences for males that sing more complex songs. Current sexual selection theory predicts that for this signal to remain an honest indicator of male quality, it must be associated with an underlying cost of development or maintenance. There has been considerable debate questioning(More)
The immunocompetence handicap hypothesis was formulated 12 years ago in an attempt to offer a proximate mechanism by which female choice of males could be explained by endocrine control of honest signalling. The hypothesis suggested that testosterone has a dual effect in males of controlling the development of sexual signals while causing immunosuppression.(More)
Bird song is a sexually selected male trait where females select males on the basis of song quality. It has recently been suggested that the quality of the adult male song may be determined by nutritional stress during early development. Here, we test the 'nutritional-stress hypothesis' using the complex song of the European starling. Fledgling starlings(More)
Songbirds sing complex songs as a result of evolution through sexual selection. The evolution of such sexually selected traits requires genetic control, as well as selection on their expression. Song is controlled by a discrete neural pathway in the brain, and song complexity has been shown to correlate with the volume of specific song control nuclei. As(More)
Vertebrates respond to environmental stressors through the neuro-endocrine stress response, which involves the production of glucocorticoids. We have selected independent, duplicate divergent lines of zebra finches for high, low and control corticosterone responses to a mild stressor. This experiment has shown that over the first four generations, the high(More)
Sexually selected signals of individual dominance have profound effects on access to resources, mate choice and gene flow. However, why such signals should honestly reflect individual quality is poorly understood. Many such signals are known to develop under the influence of testosterone. We conducted an experiment in male house sparrows in which(More)
Life-threatening infections caused by the encapsulated fungal pathogen Cryptococcus neoformans have been increasing steadily over the past 10 years because of the onset of AIDS and the expanded use of immunosuppressive drugs. Intricate host-organism interactions make the full understanding of pathogenicity and virulence of C. neoformans difficult. We(More)
There is now considerable evidence that female choice drives the evolution of song complexity in many songbird species. However, the underlying basis for such choice remains controversial. The developmental stress hypothesis suggests that early developmental conditions can mediate adult song complexity by perturbing investment in the underlying brain nuclei(More)
Developmental stress has recently been shown to have adverse effects upon adult male song structure in birds, which may well act as an honest signal of male quality to discriminating females. However, it still remains to be shown if females can discriminate between the songs of stressed and non-stressed males. Here we use a novel experimental design using(More)
The immunocompetence handicap hypothesis (ICHH) suggests that dominance signals are costly because their development is controlled by testosterone, which is immunosuppressive. Signal control therefore links an increased disease risk with a high quality signal. The chest bib of the house sparrow, Passer domesticus, is a signal known to be related to(More)