Wednesday, September 20, 2023

Marathon Hummingbird Migration Flights

Researchers estimate that the average Ruby-throated Hummingbird has a migration flight range of about 1,320 miles nonstop (photo by Paul Konrad).

Tiny Ruby-throated Hummingbirds are capable of flying more than 1,200 miles without a break according to research published in The Auk: Ornithological Advances. This research provides some of the first details about their annual fall migration from the eastern half of the United States to Central America, showing that their fall migration peaks in September and that older hummingbirds migrate ahead of younger ones.

Collecting information about birds that migrate through southern Alabama, Theodore Zenzal of the University of Southern Mississippi and his colleagues found that Ruby-throated Hummingbirds moved through the area between late August and late October, with older birds arriving earlier and in better physical condition. Using a computer program to estimate flight range based on birds’ mass and wingspan, they estimated that the average Ruby-throat has a flight range of about 1,320 miles. They also predicted that older hummingbirds and males were able to travel farther than younger hummingbirds and females.

These results suggest that older hummingbirds are more experienced and socially dominant, leaving their nesting territories earlier and flying south in less time. Whether Ruby-throated Hummingbirds migrate across the Gulf of Mexico or around the Gulf is still unknown, but the flight ranges researchers calculated mean that most Ruby-throats would be able to migrate directly across the Gulf to the Yucatan Peninsula of Mexico when weather conditions are favorable.

“The most interesting thing, in my opinion, is how some of these birds effectively double their body mass during migration and are still able to perform migratory flights, especially given that some of the heftier birds seem to barely make it to a nearby branch after being released,” said Zenzal, whose work was funded in part by the National Geographic Society.

Zenzal and his colleagues captured hummingbirds in mist nets at Bon Secour National Wildlife Refuge in Alabama during 5 fall migrations, banding and recording information about an impressive 2,729 individual Ruby-throated Hummingbirds.

“Patterns we previously had hints of from anecdotal observations are documented here with a very large sample size. It’s interesting that the young of the year migrate after adults and are quite different in their stopover phenology. This suggests there are substantial differences between flying south for the first time, as opposed to flying somewhere again as an adult,” explained Chris Clark, an expert on hummingbird behavior at the University of California at Riverside. “I think that further research on how young hummingbirds migrate, and the decisions they make would be really interesting.”

The original article was published in the All About Birds website by the Cornell Lab of Ornithology at Tiny Hummingbirds’ Incredible Migration | All About Birds All About Birds with the original scientific article published in The Auk 133(2): 237-250 Stopover biology of Ruby-throated Hummingbirds (Archilochus colubris) during autumn migration