ISLANDBIRDIET

Islands represent ecosystems with distinctive characteristics that make them ideal natural laboratories for studying speciation and adaptation. On islands, unique, isolated biotic and abiotic conditions modulate the lifestyle traits of new settlers. Since these features are repeated on islands worldwide, they give rise to parallel evolution, resulting in patterns of adaptation to the island environment - the so-called "island syndrome”. The patterns of adaptation found on islands range from morphological traits to reproductive and ecological characteristics. Although some patterns have been widely studied, like body size evolution on islands ("island rule”), others, like the diet ecology and the morphological adaptations related to resource exploitation, remained poorly explored. Yet, studying the role of diet is particularly important as is it thought to be at the origin of specific patterns of evolution on islands, such as morphological traits. In addition, it is expected to have cascading effects affecting a range of life history traits. The main objective of this project is to test if endemic island birds become more generalist in their diet than their mainland counterparts. Islands are characterized by their limited resource availability, which could derive from more generalist communities. However, island populations tend to have high population densities, which increases intraspecific competition. Intraspecific competition may be reduced by a divergence in diet and resource exploitation traits by sex, which would promote more accentuated sexual dimorphism of island species compared to their mainland counterparts. These contradictory hypotheses (generalist vs specialist) are unexplored in insular communities, especially birds. Here, we will start to explore this topic by comparing the diet ecology of bird species from the Gulf of Guinea in Africa, including endemic birds from São Tomé Island and mainland birds from Equatorial Guinea. We will capture 19 island and mainland species and collect faeces and blood and record morphological traits. Using sexing protocols to identify the sex and DNA metabarcoding techniques to characterise the diet niche breadth of our target species, we will address the following objectives: 1) Determine if island birds are more generalist consumers and present wider trophic niches than their mainland counterparts. 2) Explore if island bird diets diverge by sex, which may entail higher degrees of sexual dimorphism compared to their mainland counterparts. Finally, 3) Quantify the relationship between diet niche and morphological adaptations, such as beak morphology of island and mainland birds. This project will provide the first results that will shed light on the role of diet niche in shaping morphological traits and constitute a first step for further development in the research of insular ecology and their role in the evolution of birds.