Doctor of Philosophy (PhD)


Renewable Natural Resources

Document Type



Deforestation modifies otherwise intact expanses of forest into small, isolated fragments. In addition to fragmentation, deforestation also creates abrupt forest edges and large areas of regenerating vegetation where land is abandoned after clearing. Understanding how changes in the landscape affect the physical condition of birds is crucial for managing populations in human-modified landscapes. Here I use the biomarkers feather growth rate and feather quality (ptilochronology), fluctuating asymmetry (FA), and stress hormones from feathers (CORT), to estimate the physical condition of Amazonian understory birds living in forest fragments, second-growth forests, and continuous forests. Feather CORT revealed how fragmentation disrupts interspecific interactions; birds from continuous forest showed elevated hormone levels compared to birds from fragments, suggesting that reproduction and territorial behavior could be altered as a consequence of fragmentation. Fragmentation and edge effects also negatively affect the nutritional condition of birds, as shown by feather growth rate and quality over a 21-year period. Birds in fragments surrounded by young vegetation in the borders and the matrix had reduced nutritional condition compared to birds living in fragments surrounded by mature vegetation. Additionally, no indication of significant consequences of fragmentation on developmental stability were found when measuring FA in birds from forest fragments. Finally, birds living in 25 year-old second-growth forest had similar levels of nutritional condition compared to birds from continuous forest. Through the use of these biomarkers I was able to evidence some of the detrimental effects of fragmentation on the condition of birds, as well as to highlight the importance of second-growth forest vegetation in alleviating some of those detrimental effects, and in providing high-quality habitat for Amazonian understory birds. My findings support the high conservation value of second-growth forests in central Amazon, especially when allowed to regenerate for at least a few decades, as well as the importance of integrating fragments into the context of the overall landscape for the conservation and future of tropical forest biodiversity.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Stouffer, Philip C