IAP-25-013

Feathered Witnesses: Unravelling the Impact of Habitat Loss on Neotropical Avifauna with Stable Isotope Analysis

Like many places, Brazil has endured severe habitat loss over the last 500 years. Beginning with the arrival of the Portuguese in 1500, the introduction of sugar cane and other cash crops meant that many coastal primary forests were cleared. The expansion of cattle ranching and coffee plantations in the 17th and 18th centuries and the rubber boom of the next two centuries cleared more forest, especially in the Amazon. Finally, over the last seventy years, major infrastructure projects have increased urbanization, and further expansion of cattle and soybean agriculture westward has further contributed to the accelerated decline of pristine forests of all types.
Whilst we know the history of habitat loss in Brazil, the effects on the ecology of its avifauna are less well known. The high diversity and endemism of Neotropical birds sensitize them to environmental change. Changes in their behaviour and other natural history traits over time can give us insights into the effects of such environmental shifts. This studentship will focus on four common species of the avian subfamily of Tachyphoninae, a group of non-migratory Neotropical lowland tanagers. As omnivores, and with specimens in the Zoological Museum of the University of São Paulo collected over more than a century, they offer a unique opportunity to use stable isotope analyses to explore long-term changes in habitat use and diet across Brazil.
The studentship will elucidate how habitat loss has altered foraging behaviour, including whether closely related species now overlap or partition their ecological niches following habitat fragmentation. Findings can be extrapolated to avifauna more generally and to future environmental change. This will help inform conservation strategies and prioritise areas for protection.

The four species are Ramphocelus carbo (Silver-beaked tanager), Ramphocelus bresilia (Brazilian tanager), Tachyphonus rufus (White-lined tanager), and Tachyphonus coronatus (Ruby-crowned tanager). As well as being taxonomically related, all are omnivorous, being largely frugivorous, but also feeding on seeds, nectar, and insects. The student will measure stable isotopes in the feathers and claws of these birds, all of these being well-represented from different years and over a century in the Zoological Museum of the University of Sao Paulo. Feathers are moulted annually, principally between January and May. Date of collection and feather wear can be used to determine the year of moult in samples collected over the main moulting period.
Stable isotopes of light elements (C, N and S) can be used in mixing models to calculate the importance of major, isotopically distinguishable, dietary items, for instance, the extent of omnivory. The species overlap only in Sao Paulo State, which has seen many land-use changes, so isotope metrics would determine if the species overlap their niches or partition them, and whether this has changed over time as the environment became fragmented. Conversely, comparing each species’ isotope metrics between several biomes will determine whether these niches endure throughout each species’ range. This data would detail empirically any changes in their ecology that have taken place in the later years of anthropogenic impact and allow a discussion of the extent of these changes in different biomes.
On a smaller scale, a comparison of sex/age would allow investigation of whether males and females and/or adults and juveniles have different patterns of diet/habitat use/niche. Further, whilst these are all considered generalist species, a comparison of isotopic niche width would reveal whether there has been some degree of individual specialization over time.

Year 1

Sampling strategy / Target specimen selection / Literature review.
Sampling the MZUSP collection

Year 2

Stable isotope measurements/data analysis of museum samples
Fieldwork/modern feather sampling/Stable isotope measurements

Year 3

Data analysis
Manuscript preparation
Final review of thesis plan

Year 3.5

Thesis writing/publication corrections

The student will be registered at the University of Glasgow and primarily based at SUERC, and thus join the training programme in the College of Science and Engineering, where they will be provided with skills that are essential to a researcher at all future stages of their career. The Stable Isotope Ecology Laboratory (SIEL) is equipped with state-of-the-art instrumentation for stable isotope analysis, and the student will be trained in practical stable isotope mass spectrometry, and the use of stable isotope metrics to elucidate variation in resource and habitat use.
Training and support at Newcastle University will involve the statistical analysis of the impacts of land-use change on birds and/or foodweb analysis in the Network Ecology Group.
They will also spend significant time at the University of São Paulo’s Zoological Museum (MZUSP) collection, a treasure trove of biological diversity and a cornerstone of scientific research. It serves as a hub for biodiversity studies, providing a foundation for ecological, evolutionary, and conservation research in the Neotropical region. The collection of modern samples will necessitate fieldwork in São Paulo State, with all permits and licenses in place.