Photo: Rufous Hummingbird, Dixie Sommers
Lisa Mackem
In Virginia, hummingbird migration season peaked months ago, as Ruby-throated and Rufous Hummingbirds made their way to Mexico or Central America. One Rufous Hummingbird defied the regular migration pattern and is spending the winter in Green Spring Gardens. Birds that are present at unusual times are called “vagrants,” and show a change in their migration patterns.
Rufous Hummingbird, Charlene K. Johnson
Larry Cartwright has made many notable contributions to citizen science, including managing the winter waterfowl count for the Audubon Society of Northern Virginia since 2008 and compiling the District of Columbia’s Christmas bird count since 2004. He has noticed that Rufous Hummingbirds, although not native to this area, are becoming more frequent visitors and that their numbers have steadily increased on the Virginia state checklist for birds. He worked with Bruce Peterjohn, who recently banded the vagrant hummingbird, and explained her presence with the concept of mirror image migration. Rufous Hummingbirds usually migrate by flying east of the Rockies before veering west to Mexico. Some of them do the opposite, flying west of the Rockies and then turning east — the exact mirror image of their normal migration route. These vagrants ultimately end up along the East or Gulf Coasts.
Hummingbird feeder at Green Spring Gardens, Larry Cartwright and Bruce Peterjohn
“This has been a big year for vagrants,” Larry notes, adding that birds from wooded areas have appeared in the Great Plains and continued eastward. Fires and heat on the West Coast, which might drive birds east to find food, could also explain vagrancy. Local vagrants include a Couch’s Kingbird – the first ever seen in Virginia. Vagrant sightings are likely to continue. Larry suggests, “Once the migration pattern changes, it will probably repeat itself. It is encoded by now.”
Banding, Larry Cartwright and Bruce Peterjohn
Banding birds will continue to yield valuable information. “We couldn’t have the concept of mirror image migration without having some idea of where the birds went,” says Larry, explaining that banding will show a difference in a migration pattern for the rest of the bird’s life. The bander will also learn a bird’s gender, weight, species and approximate age. The Rufous Hummingbird vagrant is an adult female, weighs 4.3 grams and maintains no body fat. She is molting, which means she is healthy. If she returns next year, the band will show she survived the year.
Green Spring Gardens observers report that their winter guest behaves and feeds normally and has not shown signs of stress. She eats from flowering plants and from feeders that the Green Springs staff provided, and has no notable predators because she is simply too small for most predator birds and mammals. She will enter a kind of torpor at night, lowering her body temperature and metabolism to withstand the cold, and eat when she wakes up. Larry predicts that she will remain at Green Spring Gardens for the winter.