The buckthorns Rhamnus cathartica and Frangula alnus are nonnative invasive species in North America whose seeds are primarily dispersed by birds. This paper presents the first major compilation of the bird species that eat R. cathartica and F. alnus in eastern North America, where these buckthorns are most invasive and have few common congeners. Using fecal samples, observations, and an extensive literature search, I document 46 bird species that consume R. cathartica and F. alnus, and discuss which are the most competent dispersers of the seeds. I also correct a frequently-repeated belief that “blackbirds” are efficient dispersers of R. cathartica and F. alnus.
Natural Areas Journal