The Gray Catbird is typical of migratory birds that prefer the fruits of native plants, despite invasive plants dominating fruit availability in late-autumn. The Gray Catbird was among 45 species sighted in the 2019 Migratory Bird Count on Fishers Island. Ann Stinely photo for the Manomet Team Newsletter.
As migratory birds pass through stopover sites later in the season due to warming temperatures, will they begin to eat the abundant late-autumn fruit of invasive plant species rather than fruit from the diminishing number of native plants? The apparent answer is no.
This finding was the result of an in-depth study of bird-fruit interactions published in the Nov. 2019 issue of Biological Conservation, a leading international journal in the discipline of conservation science. A trio of scientists conducted their research at Manomet, a migratory stopover site for landbirds on the Atlantic coast, and a long-term bird banding site, located in Plymouth County, Mass.
Scientists observed both native and invasive wild plant species at Manomet during the 2014-15 autumn migration season and identified seeds from 469 fecal samples collected from songbirds captured during that time.
“Our results demonstrate that native fruits are an important food resource for birds during the autumn migration season and are unlikely to be replaced by abundant fruits of late-season invasive species under climate change,” scientists wrote in their study.
Twenty years ago, University of Delaware entomology professor and FIConservancy advisor, Doug Tallamy observed that insects prefer to eat native plants rather than invasives. Birds, in turn, feed on those insects, particularly when foraging for their young. This study adds striking evidence to the “native” connection, even in the face of a diminishing late-autumn native food supply due to the aggressive growth of invasive plant species.