Using data from the eBird citizen-science project, researchers patched together hummingbird sightings from more than 300,000 checklists across North America to track the central hub of migration over a five-year period. Based on the number of eBird sightings at different locations, researchers calculated the average location of hummingbird populations for each day. For example, of the estimated 2 million Calliope Hummingbirds in North America, some individuals were recorded by eBird participants during the study period from 2008 to 2013. Researchers used these sightings to then find the average location of all Calliope Hummingbirds each day and visualize overall movement of the species throughout migration.
"We could not have surveyed the entire United States 365 days a year," explained Sarah Supp, a postdoctoral fellow at Stony Brook University and lead author of the study. "Citizen-science data gave us that." The research team also included the Cornell Lab of Ornithology's research scientist Frank La Sorte and was funded by NASA's Biodiversity Program. Their study focused on 5 hummingbird species that migrate up to 2,500 miles across North and Central America: the Calliope Hummingbird, Black-chinned hummingbird, Broad-tailed Hummingbird, Ruby-throated Hummingbird, and Rufous Hummingbird.
Published in the January issue of Ecosphere, the maps revealed that the birds hopscotched between different stopover sites each year. For instance, over the five-year study, Calliope Hummingbirds shifted their central path of migration as far as 320 miles east or west between years, switching from routes focused around Tucson, Arizona, to Albuquerque, New Mexico, and from Bakersfield, California, to Las Vegas, Nevada.
According to Supp, this year-to-year variation suggests some "wiggle room" in hummingbird decision-making. The birds could be choosing sites with high-quality food, such as flowers with nectar to fuel their fast-paced metabolism. Such versatility may enable hummingbirds to respond as the rising temperatures of climate change alter the timing and location of flowering plants.
Read the entire article at: http://blog.allaboutbirds.org/2015/03/25/annual-changes-in-hummingbird-migration-revealed-by-birders-sightings/
