Where Do "Our" Hummingbirds Go in Winter?

Hilton Pond Center for Piedmont Natural History is a non-profit research & education organization in York, South Carolina USA. Bill Hilton, whose column appears in The Citizen Scientist, is a leading hummingbird specialist and his organization is planning a new hummingbird trip to Costa Rica. The Citizen Scientist received a media release about this trip, and we present it here for readers who want the ultimate hummingbird experience. Editor.

When Ruby-throated Hummingbirds depart the U.S. and southern Canada each autumn, backyard birders often wonder where they go. The answer, according to hummingbird expert Bill Hilton Jr. is: "Nobody really knows."

Hilton admits that science has long known these tiny balls of fluff bail out of North America as days grow short in fall, and that hummingbirds end up in Mexico or one of the seven Central American countries. "But," Hilton said, "no one knows, for example, if all the ruby-throats from New York State go to Nicaragua or those from Tennessee end up in Panama ."

Figure 1. In Guanacaste Province , Costa Rica , the tiny red blossoms of Jocote trees provide nectar for some winter populations of Ruby-throated Hummingbirds (adult male with red throat, above). A trap hung in this tree was used to capture ruby-throats for banding. (Photograph copyright Bill Hilton Jr.)

It's mysteries like this that have fascinated Hilton for almost a quarter century--the length of time he's been studying hummingbirds at his home base at Hilton Pond Center for Piedmont Natural History near York SC. Since 1984, Hilton has captured and banded more than 3,400 ruby-throats at Hilton Pond, many of which have returned to be recaptured in at least one later year. Hilton also was the first scientist to have one of his ruby-throats recaptured by another bander.

"Back during the 1991 fall migration," Hilton said, "a young male banded here at Hilton Pond showed up ten days later in Atlanta GA, about 270 miles to the southwest. Then in October 2000 a young female was recaptured at Mobile AL . Another color-marked female was sighted in extreme southwestern Louisiana , right on the Texas border."

Despite these three long-distance successes, most of Hilton's banded ruby-throats are never seen again.

"More important," Hilton lamented, "NONE of the perhaps 200,000 Ruby-throated Hummingbirds that have been banded in the U.S. and Canada in the past one hundred years has been reported from south of the Rio Grande River, so we really DON'T know specifically where 'our' hummers go to spend the winter."

To help overcome this dearth of knowledge about hummingbird migration, Hilton mounted two eight-day expeditions to Guanacaste Province in Costa Rica right after Christmas in 2004. He took along about two dozen teachers and citizen scientists who served as field assistants in the first organized effort to systematically study Ruby-throated Hummingbirds on their wintering grounds.

"The hardest thing that first year was just finding the ruby-throats," Hilton said, "but we finally did locate a small population and banded 15 birds during the 16-day period. That seems like an awfully small number, but it's important to remember this was the first time anyone had ever tried to capture ruby-throats in Costa Rica ."

Hilton said another excursion in late February 2006 was far more successful, with 51 ruby-throats banded in an eight-day period. "The difference was that we located a much larger population of hummingbirds that were feeding in an Aloe Vera plantation where we could run mist nets and catch more birds. We didn't capture any birds down there that were banded up north, nor have any of our Costa Rican birds shown up yet in North America , but we are still hoping."

Figure 2. Costa Rican Ruby-throated Hummingbirds also frequent aloe vera plantations (young male approaching aloe blossoms, above). Hummingbirds are caught there in mist nets, banded, and released in the hope they will return to the U.S. or Canada and be recaptured. (Photograph copyright Bill Hilton Jr.)

Now that he's located a "mother lode" of ruby-throats in Costa Rica , Hilton said he's very eager to go back to Guanacaste and try again. That's why he's organizing another eight-day trip scheduled for 3-10 February 2007, and why he's recruiting participants who'd like to go and help.

"These trips are for any adult," Hilton said, "from beginning birders to experienced field workers, and they provide an opportunity for folks to make real contributions to a scientific research project on Ruby-throated Hummingbirds."

Participants stay in comfortable rooms at Buena Vista lodge, halfway up a volcano just north of Liberia , Costa Rica , and the field work is not strenuous.

"The lodging and meals are terrific," Hilton said, "plus it's nice to be in Costa Rica in February when much of North America is cold, wet, and miserable. We spend mornings observing and banding hummingbirds and most afternoons are free for folks to explore the extensive lodge property, watching and photographing tropical flora and birds and other wildlife. The eight days fly by because we have so much fun, learn so much, and do so much great field work."

For details about the 2007 trip and information about how to register, visit the Hilton Pond Web site, specifically at http://www.hiltonpond.org/CostaRicaAnnounceMain07.html . That page includes links to lengthy write-ups about the trips in 2004-05 and 2006. Registrations are due by the end of December, so Hilton suggests you get yours in soon to reserve a place.

"The first week will certainly fill," Hilton said, "and we hope to add a second week for 10-17 February when it does. We welcome your inquires and eventual participation as we try to learn more about ruby-throats--perhaps the world's most plentiful hummingbird and one about which we actually know very little."