Islands are important centres of endemism and key ‘natural laboratories’ for the study of ecology and evolution. However, some aspects of island ecology and evolution remain poorly understood. This programme studies patterns of adaptation and speciation on islands worldwide and conducts detailed studies using birds from the Gulf of Guinea, Cape Verde and Tristan islands as study systems.

Gulf of Guinea – what can the land-bridge island of Bioko teach us?
MacArthur and Wilson’s Theory of Island Biogeography provided a theoretical framework to explain how island communities are assembled. It is particularly applicable to oceanic islands, with its predictions recently validated with empirical data from a worldwide analysis of birds, to which we contributed (Valente et al. 2020, Nature). Land-bridge islands, which have been connected to a mainland in the past, are quite distinct. In contrast to oceanic islands, land-bridge islands are formed with a complete biota – from which species can go extinct after isolation, and others may be added by migration or speciation in situ. In a study led by Luis Valente and Martim Melo in 2023, we used Bioko Island (Gulf of Guinea) to investigate how parameters of the Theory of Island Biogeography play out in such setting. Our results will have implications for understanding an increasingly fragmented world and in managing protected areas – which are more similar to land-bridge islands than to oceanic ones.

Gulf of Guinea – oceanic islands: Adding the birds of Príncipe, São Tomé and Annobón to the Barcode of Life
Laboratory work was completed in 2023, so that the whole endemic bird community of the oceanic islands of the Gulf of Guinea (Príncipe, São Tomé, Annobón) is now represented in the library of the International Barcode of Life.

The island syndrome
Organisms on islands often exhibit convergent evolution on a wide suite of traits, which are together termed the “island syndrome”. These common evolutionary outcomes are linked to the isolation, small size and stable climate associated with oceanic islands. Isolation reduces species richness on islands relative to mainland areas, limiting inter-specific competition and allowing for ecological release. Low species richness also results in fewer predators and parasites. During the last decade, our team has systematically investigated multiple aspects of the island syndrome, exploring a diverse array of traits (e.g. size, color, song, life-history) and looking at the role of different potential explanatory factors (e.g. competition, parasites, immune system).

Parasites on islands
Reduced parasite levels on islands could underlie the evolution of weaker immune systems, as suggested by the extinction of many Hawaiian birds after the introduction of an avian malaria vector. Since 2015, we have been documenting how humans impact the ‘parasite landscape’ of São Tomé Island, in a project led by Claire Loiseau, from the University of Montpellier (France). Collaborators Mathilde Barthe and Benoit Nabholz, also from Montpellier, used a large-scale genomic approach to measure the diversity of hundreds of immune response genes from our Gulf of Guinea dataset. The results show that both genetic drift and relaxed selection lead to a decrease in immune function among island birds. This confirms our worries, as human-driven habitat change is likely to alter vector-parasite-host dynamics, together with increasing the likelihood of introducing new hosts and parasites to islands.

Príncipe Island – more news on the Príncipe Scops-Owl
After the description of the Principe Scops-Owl Otus bikegila in late 2022, the team led by Martim Melo published a paper on the distribution, habitat associations, and population estimates of this Príncipe Island endemic. Based on these data, the article recommended the species be listed as Critically Endangered – an evaluation that was taken up by BirdLife International/IUCN in the December 2023 update of the IUCN Red List of Threatened Species. In parallel with this, the team published a paper detailing an automatic monitoring protocol for the species, based on the deployment of automatic recording units (Audiomoths) along transects in the area of occurrence, together with automatic retrieval of the owl calls. This will make feasible long-term monitoring of this nocturnal species across its small (~30 km2) but difficult to access range.

São Tomé - in search of yet another mysterious bird
After the discovery and description of the new species of scops-owl on the island of Príncipe, one could think that the islands of São Tomé and Príncipe, in the Gulf of Guinea, no longer hold any secrets when it comes to birds. The truth is that Martim Melo has been trying to unravel the mystery of another bird: the São Tomé Band-rumped Storm-Petrel Hydrobates cf. castro, since he first visited the islands in 1996, as part of a team led by Rita Covas and the late Luis Monteiro. In 1928, Portuguese collectors José and Virgínia Correia, working for the American Museum of Natural History (AMNH), obtained four specimens of a storm-petrel that, on a foggy night, crashed into a property, attracted by the light. These specimens at the AMNH were similar to Hydrobates castro, but larger. Within storm-petrels it is common for distinct species to be morphologically similar. In 1996 and 1997, all the islets and rocks were visited to look for nesting sites, but without success. It was then hypothesised that the species nested within the dense rainforests of the island's interior - a habitat where it is almost impossible to find nests. Later, during the long-term research on the endemic birds of these forests, the presence of storm-petrels was confirmed by vocalisations that could be heard at night during several months of the year. Although no nests have yet been found, it is now certain that they do indeed nest in the forest.

In 2023, a new team was put together by Fitz Research Associate Robert Flood to try to solve this mystery. The main objective is to determine which species of storm-petrel nests on São Tomé, the alternatives being: a population of Hydrobates castro, a population of the Cape Verdean species H. jabejabe, or a new species.

In June 2023, Robert Flood and Martim Melo joined a team of eight with the aim of gathering as much information about the species as possible and trying to capture individuals to obtain essential blood samples for genetic analyses. There were night-time surveys in exposed areas of the coast close to the forest, four pelagic trips, and camps set up inside the forest to try and locate nests. The pelagic trips (c. 12 kilometres offshore) proved to be the most fruitful, allowing dozens of individuals to be observed and photographed. The birds were lured with oil and fish guts and a large handheld net was used to try and catch them - which was not successful. Martim Melo did, however, manage to capture a Wilson’s Storm-petrel Oceanites oceanicus, which led to an unexpected discovery: the individual captured (along with others photographed) appears to belong to the subspecies chilensis - which nests in the Cape Horn region - and not the nominal subspecies as previously thought. A feather sample was taken to confirm this hypothesis. In July and August, local collaborator Martim Veiga was able to measure and obtain samples from four individuals obtained in the same way as José and Virgínia Correia: individuals that are attracted to lights on foggy nights, in this case at the Agripalma palm oil factory. In September, Martim Melo returned to São Tomé where he went out to sea and obtained more samples and measurements from two individuals who were also attracted by the lights from the Agripalma factory. In a short space of time, Martim was able to obtain measurements and samples from six individuals, which will contribute to solving the mystery. Of the six individuals attracted by the lights, two died and four were released. Kristof Zyskowski, head of vertebrate collections at the Yale Peabody Museum, travelled to Portugal to prepare the skins of two dead specimens.

Cape Verde Islands
The Iago Sparrow Passer iagoensis, endemic to the Cape Verde archipelago, makes an excellent model for the study of adaptation in the wild. It occurs across a wide aridity gradient on 13 islands and islets, allowing insights into how birds may adapt to an increasingly arid world. It is also a good model to study the evolution of commensalism, as humans only colonised the archipelago 500 years ago, and some islands remain uninhabited. Fitz Research Associates Martim Melo and Rauri Bowie are collaborating with Ângela Ribeiro, Mark Ravinet and José Cerca on a project that combines fieldwork and genomics to untangle the Iago Sparrow’s recent micro-evolutionary history.

Activities in 2023

  • Laboratory work to obtain barcodes for all endemic birds of the oceanic islands of the Gulf of Guinea was completed.
  • Work on the Art and Science project associated with ongoing research on São Tomé progressed well. A 25-min video-performance (Or l’Oiseau) was produced with English, French and Portuguese versions) short documentary-outreach videos were finalised, and funds were obtained to create an exhibition that will travel between France, Portugal, and São Tomé.
  • The search for the mystery São Tomé Storm-petrel was relaunched.


  • The first genetic samples were obtained for the Band-rumped Storm Petrel from São Tomé, together with a wealth of photographs to build our understanding of this mystery taxon.
  • Two papers were published in international journals:
    • Ponti, R., Doutrelant, C. and Covas, R. 2023. Strength of the ‘island rule’ in birds is positively associated with absence of avian predators. Biology Letters 19: 2022053620220536
    • Melo, M., Covas, R., et al. 2023. DNA Barcode library of the endemic-rich avifauna of the oceanic islands of the Gulf of Guinea. Biodiversity Data Journal 11: e110428. .

Impact of the project
This project is uncovering novel patterns of adaptation in island birds and investigating the mechanisms underlying these adaptations. The findings contribute to our understanding of the ecology and evolution of island environments. Given the large number of species endemic to islands worldwide and the numerous threats they face, our work will inform conservation strategies for island species. The ongoing ‘art & science’ project will have a variety of outputs that will improve public outreach.

Key co-supporters
FCT - Portuguese Science and Technology Foundation; CNRS-France (PEPS); Marie Sklodowska-Curie Grants.

Research team 2023

Dr Martim Melo (FIAO, UCT/CIBIO, U. Porto)
Dr Claire Doutrelant (CNRS/FIAO, UCT)
Dr Rita Covas (FIAO, UCT/CIBIO, U. Porto)
Dr Robert Flood (FIAO, UCT)
Dr. Claire Loiseau (University of Montpellier)
Dr Ângela Ribeiro (IPVC, Portugal)
Dr Mark Ravinet (U. Oslo)
Dr José Cerca (U. Oslo)
Dr Martin Stervander (National Museum, Edinburgh)
Dr Luis Valente (Naturalis Biodiversity Center, Leiden)
Dr Ricardo Lima (cE3c, U. Lisbon)
Prof. Bengt Hansson (Lund U.)
Emer. Prof. Peter Ryan (FIAO, UCT)
Dr Raquel Ponti (CIBIO, U. Porto)
Dr Ana Leitão (CIBIO, U. Porto)
Prof. Rauri Bowie (U. California Berkeley)