Overseas seed dispersal by migratory birds

Area of Science:

• Ecology
• Biogeography
• Ornithology

Background:

• Long-distance dispersal (LDD) is vital for species colonization of new habitats.
• Birds are recognized as significant LDD vectors for sessile organisms like plants.
• Direct quantification of LDD beyond regional scales, especially via birds, has been lacking.

Purpose of the Study:

• To directly observe and quantify long-distance seed dispersal by migratory birds.
• To investigate the role of migratory birds in transporting seeds to oceanic islands.
• To understand the implications of bird-mediated seed dispersal for plant distribution and colonization.

Main Methods:

• Utilized GPS-tracked wild falcons to intercept migratory birds in flight.
• Sampled seeds carried within the digestive tracts of captured migratory birds.
• Analyzed the origin and destination of seeds and the migratory routes of birds.

Main Results:

• Migratory birds were confirmed to transport viable seeds over hundreds of kilometers.
• Up to 1.2% of migratory birds reaching Alegranza Island carried seeds.
• Dispersed seeds were primarily of species not native to the Canary Islands, highlighting environmental filters.

Conclusions:

• Migratory birds are effective vectors for long-distance seed dispersal, connecting mainland and island ecosystems.
• Billions of migratory birds may transport millions of seeds annually, influencing plant biogeography.
• LDD by birds can drive rapid range expansions and colonization, despite environmental filtering.