A new study using sightings reported to eBird found that many migratory birds time movement to match “green-up” or emergence of leaves, as they travel north and south. Frank La Sorte, a research associate at the Cornell Lab of Ornithology, and Catherine Graham, a researcher at the Swiss Federal Research Institute in Switzerland, found that migratory birds that eat plants and seeds moved north in sync with foliage emergence in the spring. This is the first study of its kind to examine migration timing in relation to seasonal changes in greenness for a large number of North American migratory bird species that feed on a variety of foods including plants, seeds, nectar, insects, birds, and small mammals. Their findings were published last week in the Journal of Animal Ecology.
La Sorte and Graham used data from satellites to estimate the greenness of vegetation year round and cross-referenced that data with observations submitted by eBirders for 230 North American migratory bird species from 2006 through 2018.
