Alborán: Gulls between Europe and Africa

Since ancient times, the remote island of Alborán has been a haven for seagulls. Lord Lilford already saw them during one of his expeditions back in 1879. And indeed, as mentioned in Between Africa and Europe: The Natural History of Alborán Island, «one of the first peculiarities that capture the visitor's attention on Alborán Island is (…) the cloud of seagulls that circle the surroundings, in a constant cacophony of cries and flights, from the moment one disembarks at its docks until departure». Seabirds whose diet, at most, we could guess was based on fishing discards from boats traditionally operating near the island. 

But what is the true reach of their flights? Are they creatures confined to this small piece of land and the waters that surround it? or, on the contrary, do they actually belong to something far greater, like the network of colonies where they nest, the sea, the ocean, or the sky itself? Perhaps they are perpetual travelers of the "remote West," as the ancient Greeks and Phoenicians once called the westernmost part of the Mediterranean.

Mariano Paracuellos

Fieldwork on Alborán Island

Tucked between the Iberian Peninsula and North Africa, the island of Alborán has become a key site for the study of two emblematic seabirds: the Audouin’s gull (Ichthyaetus audouinii) and the yellow-legged gull (Larus michahellis). From May 21st to 24th, 2025, researchers from the University of Barcelona conducted a tracking campaign to better understand how these species use marine space and interact with human activities.

The Audouin’s gull, endemic to the Mediterranean, is currently classified as Vulnerable by the IUCN and faces threats such as habitat degradation, reduced fishery discards, and competition with more generalist species. The yellow-legged gull, while more abundant and adaptable, has recently shown signs of decline in parts of its range, prompting closer monitoring.

Collaborative Research Efforts

This fieldwork was carried out within the framework of the AMPLIAMAR project, supported by Plearmar programme the Fundación Biodiversidad and Spain’s Ministry for the Ecological Transition and Demographic Challenge (MITECO).

Led by Dr. Jacob González-Solís and research assistant Céline van Weelden, the team deployed GPS-GSM solar-powered tracking devices on 15 individuals (10 Audouin’s gulls and 5 yellow-legged gulls). These devices will allow researchers to follow the birds' movements during the breeding season and beyond, contributing essential information to marine spatial planning and conservation strategies.

We would like to sincerely thank Víctor García Matarranz (Dirección General de Biodiversidad, Bosques y Desertificación, Ministerio para la Transición Ecológica y el Reto Demográfico) and José María Díaz Hernández (Estación de Anillamiento Lorenzo Garcia; EALG , SEO/BirdLife) for their support, as well as the Junta de Andalucía and the Secretaría General de Pesca for granting the necessary permits to carry out this fieldwork on Alborán Island. We are also deeply grateful to the military detachment stationed on Alborán Island for their hospitality during our days of work, as well as for providing access to their facilities and vessel for transportation. Additionally, we thank Spain’s Marine Reserves, especially Julio, for their invaluable assistance in facilitating our arrival to the island. 

Project Objectives

To enhance marine conservation in Spain by tracking seabird movements, identifying areas of ecological importance, and integrating this knowledge into marine spatial planning and the expansion of protected area networks such as Natura 2000 and RAMPE.  (To read more about AMPLIAMAR proejct...)

Through these efforts, AMPLIAMAR is contributing to the EU objective of protecting 30% of marine areas by 2030.

To carry out this work, the team used OrniTrack GPS-GSM devices manufactured by Ornitela:

• OrniTrack-20 (19–20 g) for Audouin’s gulls

• OrniTrack-25 (23–25 g) for yellow-legged gulls

These lightweight, solar-powered units transmit high-resolution location and sensor data via GSM/4G networks. Devices are programmed remotely and record positional, environmental, and behavioral information including altitude, temperature, acceleration, and light intensity.

Each tracker was fitted using a harness and all birds were handled under strict animal welfare protocols to minimize disturbance and handling time.

To capture the gulls safely for tagging and sampling, researchers used clap traps—a spring-loaded, remotely triggered trap placed directly over active nests. This method is commonly used in seabird research due to its precision and low risk, allowing the capture of incubating adults with minimal disturbance to the nest or surrounding colony. In the case of yellow-legged gulls, which were no longer incubating, individuals were captured using a leg-loop system assisted by a fishing rod to gently secure them from a distance. 

Preliminary Insights

Of the 15 devices deployed, 13 transmitted data successfully (87%). Early movements have shown marked differences between the two species:

• Audouin’s gulls (orange) remained strictly coastal, with some individuals traveling between the Iberian and Moroccan coastlines, always within marine environments.

• Yellow-legged gulls (green) showed more variable movement, with one individual venturing up to 55 km inland in Morocco, stopping at waste facilities and a water treatment plant—demonstrating the species’ adaptability and interaction with human-modified landscapes.

These insights are already helping researchers understand species-specific responses to anthropogenic pressures and refine conservation priorities.

Looking Ahead

This fieldwork was carried out within the framework of AMPLIAMAR , a project led by Professor Jacob González-Solís and coordinated by early-stage researcher Diego Vicente, both from the Biodiversity Research Institute (IRBio) at the University of Barcelona. The project aims to expand Spain’s network of Marine Protected Areas by identifying Key Biodiversity Areas (KBAs) for seabirds and other marine species. By deploying GPS-GSM trackers on Audouin’s gulls and yellow-legged gulls in Alborán, we contributed to one of AMPLIAMAR’s core objectives: improving knowledge of seabird movements in under-studied sites. The data gathered over the coming weeks will enhance our understanding of how these species use marine space—particularly in relation to human activities—and support the identification of KBAs in the Alborán Sea. Ultimately, we hope these findings will contribute to expanding the current RAMPE and Natura 2000 networks, helping safeguard important marine habitats through science-based conservation planning. It is supported by the Pleamar programme from Fundación Biodiversidad, under the Ministry for Ecological Transition and Demographic Challenge. AMPLIAMAR project is also co-financed by the European Maritime, Fisheries, and Aquaculture Fund (FEMPA) of the European Union.

As the team begins to analyze the GPS data and biological samples collected during the campaign, results will contribute to a clearer picture of how seabirds navigate the complex marine environment of the Alborán Sea. Combined with spatial data on human activity, these findings may feed into proposals for new Key Biodiversity Areas and strengthen marine protection in this biodiversity-rich region.

The fieldwork in Alborán illustrates how targeted research using modern technology can inform marine conservation at a time when seabirds—and marine ecosystems as a whole—face growing challenges.

Stay tuned for more updates from the project team as we continue uncovering the hidden journeys of seabirds across the Mediterranean.