Seagulls: Guardians of Olive Seed Dispersal in the Balearic Islands

• Seed dispersal plays a fundamental role in the reproduction, colonization, and survival of olive trees, among other plants.

Seed dispersal through ingestion by vertebrates is a vital element for plant reproduction. This mechanism is known as endozoochory.

Although this mechanism has been extensively studied in recent decades, most studies have focused on specialized frugivorous animals, overlooking granivorous or omnivorous birds that also play a crucial role in seed dispersal, even over long distances, more than previously believed.

A recent study involving a group of researchers from IMEDEA reveals the vital role of yellow-legged gulls in the olive seed dispersal in the Balearic Islands. This role gains particular importance in island ecosystems like the Balearics, where the presence of specialized frugivores is limited, requiring long-distance dispersal for the colonization of new areas

Photo: Yellow-legged Gull (laurus michahellis) Author: Ignacio Súarez

Seabirds, such as seagulls, are key players in this process. Their mobility, coupled with their ability to breed in islands with sparse vegetation, makes them significant vectors for seed dispersal.

A study conducted in the Balearic Islands examined the behavior of Yellow-legged Gulls (Larus michahellis), primarily feeding on olives, both domestic and wild varieties. Using GPS tracking technology on marked gulls, it was discovered that these birds disperse olive seeds over significant distances, even between different islands in the archipelago. Surprisingly, domestic olives were dispersed over greater distances and in specific directions, potentially facilitating their colonization and expansion under suitable environmental conditions.

In summary, this study highlights the crucial role of seagulls in long-distance seed dispersal in island ecosystems, especially for large fruits like olives.

These findings underscore the importance of understanding and conserving interactions between birds and plants in these unique environments.

Reference:

Ando, H.; Martín-Vélez, V.; Tavecchia, G.; Traveset, A.; Jiménez-Martín, I.; Igual, J. M.; Martínez-Abraín, A.; Hervías-Parejo, S. 

"Gulls contribute to olive seed dispersal within and among islands in a Mediterranean coastal area"