Collaborative Research: Forest fragmentation and climate change result in understory warming that adversely affects tropical avian biodiversity at the BDFFP.

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Tropical birds are in trouble, especially those that eat mostly insects. Population declines are taking place in both large and small areas of forest, although at a faster rate in small forests or “fragments”. Exposure to sun along the edges of fragments causes their interior to become hotter and drier, which reduces habitat quality for many birds. Scientists do not know exactly how warmer and drier conditions cause trouble for birds, but they think it is due to less food and more stress. In this study, researchers will study whether longer and hotter dry seasons are responsible for the decline of birds in continuous forests and which species are most susceptible to changes in climate. To do this, they will collect physiological data and combine it with climate data from the past forty years to understand the relative role of climate and forest condition on birds’ diet, health and survival. Results will improve our understanding of how forest loss and climate change affect birds, and ways in which we might mitigate the loss of biodiversity. The PIs posit that remnant bird communities in forest fragments are a precursor of future bird assemblages in continuous forest. Increased physiological stress and/or dietary specialization are likely determinants of avian survival and reproductive success under global change. This project has three objectives: (1) Assess the impact of climate change as the primary driver of long-term bird declines in continuous forest at the Biological Dynamics of Forest Fragmentation Project (BDFFP) through the inclusion of 40 years of climate and bird banding data in a series of survival models. (2) Determine the interactive effects of climate change and fragmentation on the viability of bird populations at BDFFP through demographic modeling. (3) Measure how dietary and behavioral specialization of model bird species (two experiencing declines: Turdus albicollis and Willisornis poecilinotus, and two experiencing population growth: Calyptorhynchus spirurus and Pithys albifrons) interact with variation in understory microclimates to affect fitness. Researchers will measure diet using a combination of eDNA and isotopic niche analysis (from fecal samples, feathers, and toe nails) and stress using a combination of B-OH butyrate, triglyceride, and corticosterone, across seasons and between continuous and fragmented forests. Results will yield mechanistic insights into the role that niche specialization and understory drying play in driving demographic responses of tropical birds to forest fragmentation and climate change.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.