Limited potential for bird migration to disperse plants to cooler latitudes

Climate change is forcing the redistribution of life on Earth at an unprecedented velocity. Migratory birds are thought to help plants to track climate change via long-distance seed dispersal. However, seeds may be consistently dispersed towards cooler or warmer latitudes depending on whether a plant species fruiting period coincides with the northward or southward migrations. Here we assess the potential of plant communities to keep pace with climate change via long-distance seed dispersal by migratory birds. To do so, we combine phenological and migration information with data on 949 seed-dispersal interactions between 46 bird and 81 plant species from 13 woodland communities across Europe. While most plant species (86%) in these communities are dispersed by birds migrating south, only 35% are dispersed by birds migrating north, a subset phylogenetically clustered in lineages with fruiting periods that overlap with the spring migration. Moreover, only a few Palearctic migrant species provide most of this critical dispersal service northwards. The potential of migratory birds to assist a small non-random sample of plants to track climate change latitudinally is expected to strongly influence the formation of novel plant communities, thereby affecting their ecosystem functions and community assembly at higher trophic levels