Only doing half the job: Frugivorous birds facilitate the spread but not the germination rate of invasive Cotoneaster pannosus

• Indigenous birds and mammals are consumers of Cotoneaster pannosus fruits. • Birds swallow fruits whole and excrete viable seeds. • Pulp removal enhances germination rate regardless of whether this is mechanical or through bird ingestion. • Germination rate and success were extremely low across three different treatments. Shrubs from the Rosaceae family have become emerging invasive alien plants in the montane grasslands of South Africa. The most common of these species include Cotoneaster pannosus and Pyracantha angustofolia . We explored the seed dispersal and germination of C. pannosus, a species notorious for forming monocultures that can outcompete native plants. This was achieved through the identification of seed dispersers using observations and remote cameras, and by exploring the germination success and rate of C. pannosus seeds ingested by frugivorous birds using laboratory feeding experiments. Footage and direct observations revealed birds and mammals consumed C. pannosus fruits. Field observations and feeding experiments showed that birds ate whole fruits, and the seeds passed through the gastrointestinal tract within 15 min. The germination success was <8 % for the treatments (whole fruits, manually de-pulped fruits, defecated seeds). Germination rates for seeds that birds defecated were faster (192 days) than manually depulped seeds and seeds buried as whole fruits, although differences between treatments were non-significant. Birds and mammals were confirmed as consumers of C. pannosus fruits and, therefore, seed dispersers, but unlike other invasive Rosaceae species, such as P. angustifolia , ingestion by birds is not as crucial for speeding up germination. However, pulp removal improved the rate of germination, regardless of whether this is achieved through bird ingestion or manual de-pulping. Birds are, therefore, one of the disperser taxa driving the spread of C. pannosus in the grassland biome; however, the low germination rate is slowing the spread of the invasion.