Islands are important centres of endemism and key natural laboratories for the study of ecology and evolution, but they are also hotspots of human-driven extinctions. This programme investigates how island communities are assembled (island biogeography), how new species arise (speciation), how populations adapt to island environments, and assesses threats to their persistence. Our research focuses on birds from the Gulf of Guinea, Cape Verde and Tristan islands.

Island birds are more generalist than their mainland counterparts
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 relative to mainland areas, limiting interspecific competition and allowing for ecological release. Low species richness also results in fewer predators and parasites. During the last decade, we have investigated several island syndrome traits (e.g. size, colour, song, life history) and their explanatory factors (e.g. competition, parasites, immune system).

In 2025, we published a paper showing that island birds tend to evolve morphologies associated with a more terrestrial and sedentary lifestyle, linked to lower interspecific competition and fewer predators on islands. We are exploring how reduced interspecific competition and low resource availability (due to small land areas) combine to cause island species to evolve more generalist dietary niches. On an expedition to Príncipe Island in June, we started collecting bird faeces so we can eventually test this hypothesis. Diet will be inferred from the faeces using a metagenomics approach as part of Lynn Robey’s MSc at the Research Centre in Biodiversity and Genetic Resources (CIBIO) in Portugal.

The São Tomé storm-petrel mystery
Dr Martim Melo has been trying to unravel the mystery of the São Tomé Storm-petrel since his first visit to the islands in 1996, and recently he and a team led by Dr Robert Flood solved this mystery. A combination of observations in the southern forests of São Tomé and from boats offshore, together with genetic sequences from six birds attracted to the lights of a palm oil factory, has shown that these storm-petrels are closely related to the Cape Verde Storm-petrel Hydrobates jabejabe. The unexpected discovery of a band-rumped storm-petrel skin from 1845 at the Vienna Museum, which we suspect may belong to the population from São Tomé, sheds further light on the story. The results will be published in 2026. We have also confirmed that this population breeds in the primary forests of the island – and, surprisingly, all evidence suggests that it breeds in the canopy, rather than in holes in the ground. There is still much to explore in 2026, with the help of drones and professional tree climbers.

The Príncipe Thrush
In 1997, Martim observed individuals of the São Tomé Thrush Turdus olivaceofuscus on Príncipe Island, with the only previous record made by José Correia in 1928. The Príncipe population was classified as a subspecies (xanthorhynchus), with the nominate subspecies being abundant on São Tomé Island. The population on Príncipe appeared to show striking morphological differences from the nominate subspecies. In 2007, Martim and Martin Dallimer surveyed all of Príncipe to estimate the population size of this rarely seen subspecies and collect data to clarify its taxonomic status. This work resulted in the classification of the Príncipe Thrush as a distinct species T. xanthorhynchus and, based on population estimates, its classification by the IUCN as Critically Endangered.

Our long-standing collaborators from the Príncipe Foundation regularly conduct biodiversity monitoring transects on the island and in the Natural Park (which includes the entire area occupied by the thrush). In 2024, they suspected that the number of Príncipe Thrushes might be declining, although the species’ rarity makes it hard to robustly infer a population decrease. Because their transect methodology is not specifically targeted at the thrush and differs from the methodology used in 2007, we decided to repeat the 2007 transects to obtain an objective assessment of the situation. Martim joined forces with Ricardo Lima (CE3C, Lisbon) and the Príncipe Foundation to repeat the 2007 survey. This entailed fieldwork in the most difficult to access locations on the island, including Pico do Príncipe and Pico Mesa. Fortunately, the recent survey results do not point to a decline in this species, but they do confirm its extreme rarity, raising concerns about its long-term viability.

Cape Verde sparrows
The Iago Sparrow Passer iagoensis, endemic to Cape Verde, is an excellent model for studying climate adaptation as it occupies a wide aridity gradient on 13 islands. It also exhibits a range of degrees of commensalism, as humans only colonised the archipelago 500 years ago, and some islands remain uninhabited. Martim and Prof. Rauri Bowie are collaborating with Dr Ângela Ribeiro, Dr Mark Ravinet and Dr José Cerca on a project that combines fieldwork and genomics to understand the sparrow’s evolutionary history. The species succeeds by being a ‘super-generalist’ in a harsh environment characterised by scarce, unpredictable food resources. Surprisingly, sparrows from the Rombos, two small islets, differ phenotypically and genetically from all the other populations. The genes determining bill size and shape are the same as those causing bill diversification in Darwin’s finches, but the mutations probably evolved after the islands were colonised. These results are reported in a paper currently in its second round of revisions for publication in Molecular Ecology.

Activities in 2025

  • Two expeditions to Príncipe Island for the Príncipe Thrush survey and sample collection for the study of island bird diets.
  • First ringing course on Príncipe Island, for the staff of the terrestrial conservation department of the Príncipe Foundation.
  • Completion of the work to resolve the identity of the storm-petrel population breeding on São Tomé and initiation of the search for nests in the forests.

Highlights:

  • A global analysis of morphological traits in island birds and their mainland counterparts, led by Dr Raquel Ponti, confirmed that birds on island evolve traits favouring a more terrestrial lifestyle. The study was published in Global Ecology and Biogeography.
  • The Portuguese version of Biodiversity of the Gulf of Guinea Oceanic Islands: Science and Conservation, originally published by Springer, was launched. This version was coordinated by Martim (co-editor of the original version). The launch on São Tomé was used to organise a week-long program on biodiversity-related activities around International Biodiversity Day (22 May). Both the English and Portuguese versions are freely available online.
  • The arts and sciences project ‘Obô’ (the São Tomé name for primary forest) was hosted for two months in the Biodiversity Gallery of the Natural History and Science Museum of the University of Porto. This included parallel activities such as a performance with live music, drawing, and photo projection by the French artist and musician Fisher0men and a live video narrative (with shearwaters as protagonists!) by NY artist Ellie Ga.
  • Funding obtained from the Dutch Research Council (NWO) for a three-year project on community assembly on land-bridge islands (PI: team member Dr Luis Valente). The project will have a global component that will source data from databases and museums, and there will be a population genomics component using Bioko Island (Gulf of Guinea) as a study model.
  • Although no fieldwork was conducted at Tristan in 2025, a paper on the distribution and abundance of Gough Moorhens Gallinula comeri on the main island of Tristan was published in Bird Conservation International.

Key co-supporters
FCT– Portuguese Science and Technology Foundation; CNRS-France (PEPS); Marie Sklodowska-Curie Grants; Royal Society for the Protection of Birds; Tristan Conservation.

Team leaders and collaborators:
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 (U. 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)

Student:
Lynn Robey (MSc, CIBIO, U. Porto)