Climate change is rapidly reshaping animal populations and their distributions. In the Tropics, little is known of how birds will physiologically adapt to a warmer planet, yet there is evidence of upslope shifts towards cooler zones along mountainous gradients. As a consequence, montane bird populations are predicted to become more homogenized, as only those species capable of tolerating increasing temperatures would adapt and persist alongside colonizing species from the lowlands. In addition, warming conditions may continually push mountaintop birds upwards towards an “escalator to extinction”. To support these predictions, there is an imperative need to generate data on the thermal physiology of tropical birds. Birds seems to follow the climatic variability hypothesis, in which species that are subjected to a broader range of temperatures are more tolerant to climatic variation and this pinpoints the greater risk for tropical resident species. Some experimental studies support this hypothesis, concluding high thermal tolerance in widespread species, while others underscore the vulnerability of montane and endemic birds. Significant upward shifts of tropical montane birds may not be enough to track warming environmental conditions fast enough, making them more vulnerable to the simultaneous effects of land use intensification. However, the persistence of forest fragments and habitat heterogeneity amidst agricultural landscapes can modulate bird species composition and make these agroecosystems less hostile to birds.

Project aims

• Examine thermal tolerance and vulnerability of tropical montane birds whenever the upper critical limits of the thermoneutral zone matches or mismatches projected maximum ambient temperatures.
• Evaluate if increasing temperatures have led to past community turnover and could lead to future distributional range shifts of tropical montane birds immersed in an agricultural matrix.
• Determine how the intensity of land use practices (e.g. shaded vs. non-shaded coffee farms) can modulate bird assemblages facing increased temperatures.

Funding

Funded by the Faculty of Life Sciences of the University of Vienna

Participants

Co-Pi: Stefan Dullinger
Co-PI: Leonida Fusani
Co-PI: Christian Schulze
Team member: Otto Monge