Investigating the differences in health, pathogen prevalence and diversity of wild birds inhabiting shade-grown coffee plantations and forest fragments in San Luis, Costa Rica
Hernandez-Divers, Sonia Maria
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This dissertation describes the differences in pathogen prevalence and diversity, as well as indirect health parameters of two avian communities in San Luis, Costa Rica. In the tropics, the balance between preserving forests and the ecological services they provide, and deforestation for human development is a major challenge. Sustainable agricultural practices, such as shade-grown coffee, have been promoted as areas that can act as forest surrogates, thus increasing available habitat for avian populations. However, their potential role as ecological sinks has not been studied. In this dissertation, I examine the potential role of shade-grown coffee plantations as potential areas where birds may harbor a higher level or diversity of pathogens than birds living in nearby forest fragments. I measured the level and diversity of a variety of directly transmitted (paramyxovirus, Mycoplasma sp.), vector-borne (blood parasites) and indirectly transmitted (e.g. endoparasites) pathogens in a community of birds inhabiting shade-grown coffee plantations and compared it to a community of birds inhabiting forest fragments. I also measured indirect health indices such as body condition and body mass. Some interesting findings include the presence of antimicrobial resistance pattern of the bacterial flora in birds inhabiting sun-grown coffee plantations, but not found in shade-grown coffee plantations or forest fragments. Additionally, there were differences in the level of infection with Haemoproteus sp., a blood parasite, in the White-eared Ground-sparrow (Melazone leucotis) by habitat type, such that individuals of this species living in shade-grown coffee plantations had a higher prevalence of Haemoproteus than those living in forest fragments. Finally, I propose a variety of mechanisms that could lead to this difference, one which is the introduction of backyard chickens, and explore the pathogen prevalence of backyard chickens in the region. I also examined the avian community composition of birds captured in shade-grown coffee and forest fragments and noted that the overall trends implies that forest obligate species colonize shade coffee at lower rates than forest fragments, and do not persist in coffee to the same extent as in forest fragments. Forest obligate species had lower interseasonal persistence in shade coffee plantations than in unfarmed forest fragments.