Different species of seabirds can successfully thrive on small, isolated islands, even when they share the same fish resources. A researcher from Uppsala University has contributed to the development of an innovative mathematical model that enhances our understanding of this unique ecosystem.
“Our model shows that coexistence occurs naturally when species differ in their ability to catch fish and to efficiently fly long distances to the area where they catch fish,” says Claus Rüffler, Associate Professor of Animal Ecology at Uppsala University.
Seabirds often breed in enormous colonies, sometimes with hundreds of thousands of pairs. Ecologists have long been fascinated by the factors that determine the size of these colonies. Researchers from Uppsala University and the University of Lausanne have created a mathematical model that explores how seabirds’ fishing choices influence the distribution of fish around their breeding sites, how this impacts bird population sizes, and how multiple bird species can coexist in the same colony while feeding on the same resources.
According to fundamental ecological theory, two distinct species cannot thrive on the same limiting resource; typically, the stronger competitor will outcompete the other, leading to extinction. However, researchers are exploring the fascinating dynamics that enable multiple seabird species to coexist while nesting on a single isolated island.
“For all species, it would be most beneficial to fish close to the island because it would cost them the least energy. However, bird species differ in traits such as wing length and how deep they can dive. Our model shows that different species, all maximizing their energy intake, automatically use different distances from the colony,” says Rüffler.
The model anticipates that seabirds will strategically partition the surrounding waters into distinct circular zones, allowing each species to fish within its own designated area, thus ensuring coexistence without competition.
“Our model is fundamentally about coexistence and biodiversity. Understanding this is important in itself – we humans have a desire to understand how nature works. However, such an understanding is also crucial for any management strategy for an endangered ecosystem. Also, we believe that our results contribute to ecology more generally because the mechanism for coexistence discovered in our model likely applies to systems other than seabirds,” Rüffler concludes.
Journal reference:
- Claus Rueffler and Laurent Lehmann. Central place foragers, prey depletion halos, and how behavioral niche partitioning promotes consumer coexistence. PNAS, 2024; DOI: 10.1073/pnas.2411780121
