hummingbird

The majority of hummingbirds encountered near the San Pedro House are black-chinned hummingbirds.

“To band a bird is to hold a ticket in a great lottery,” wrote Aldo Leopold in “A Sand County Almanac.” In early October the Southeastern Arizona Bird Observatory (SABO) concluded its 24th season of banding hummingbirds on the San Pedro Riparian National Conservation Area (SPRNCA). These “lottery tickets” of banded birds give us some insight into migration, longevity, site fidelity and other aspects of these bird’s lives that are otherwise difficult to know.

In addition, a long-term study like this one gives us a window on changing habitat and climate.

Maintaining a study for this long would not have been possible without the constant presence of the Friends of the San Pedro River and their dedicated volunteers at the San Pedro House who keep the feeders up, cleaned and filled, the grounds maintained and the bookstore open.

Over the years of the study we have banded over 8,000 hummingbirds on the river. The great majority (>80%) have been Black-chinned Hummingbirds, but we have recorded 11 species at the river. Some species are expanding their range – Broad-billed hummingbirds used to be rare on the river and are now encountered regularly. Twenty percent of the birds we catch are birds we have already banded, and these are the birds that tell us about site fidelity and longevity. It’s no surprise to anyone who maintains a hummingbird feeder that hummingbirds return to the same area each year to nest. Some banding sessions, in late May when the migrants have already passed through and we have only the resident birds on the river, almost all the birds we capture are banded.

Even in migration, we have birds that we encounter the same week in April nearly every year. This speaks to the importance of habitats like the San Pedro. Our oldest bird to date was banded as an adult and recaptured 9 years later. At least 10 years old, she held the longevity record for Black-chinned hummingbird for a while. She even had a few grey feathers the last couple of times we saw her.

Migration is a little harder to pinpoint with banding. With larger birds, even warblers, researchers now have the technology to attach tiny transmitters to the birds to track their movements without having to enter in Leopold’s lottery. For those with the equipment and budget, this has given them great information on the mysteries of migration. I doubt that we will ever have transmitters small enough to track a 3-gram hummingbird, but then, I never thought we would be carrying in our pockets a computer we can ask directions.

The current rule of thumb for hummingbird “foreign recaptures (a bird wearing someone else’s band)” is to expect perhaps about one per thousand birds banded and we are running true to form. We’ve had birds banded on the San Pedro show up in Montana, New Mexico, Ramsey Canyon and the Chiricahuas and have caught birds banded in Idaho, Utah, Patagonia, Sabino Canyon, Rio Rico and Alpine, AZ. Slowly, a picture of migration patterns is forming.

The timing of migration is a little easier to look at and the birds are definitely arriving earlier and staying later than they did 24 years ago. We began banding the first week in April in 1995 and, for many years, our first couple of banding session would see no birds or only one or two. In 2019 we banded over 20 birds on March 29th. We may also need to extend our banding season into October to cover the southbound migration.

I must admit our ulterior motive in beginning our study was to show the importance of the San Pedro as a migratory corridor for hummingbirds. To make people who don’t care about Willow Flycatchers, Yellow-billed Cuckoos and Huachuca Water Umbel have a personal connection to the river through “their” precious hummingbirds.

My favorite anecdote to this point involves a rufous hummingbird banded several year ago in his southbound migration. They are usually “here today, gone tomorrow” so we were surprised to recapture him two weeks later. Taking his data again, we confirmed he had gone from weighing 3 grams to 4 grams and from no visible fat to heavy fat. He had arrived at the San Pedro with his tank on empty in a year when the red morning-glory filled the old field near the San Pedro House. In two weeks, he had filled his tank and was ready to resume his journey. The importance of these migration corridors and refueling stops to neotropical migrants cannot be overstated.

Banding at the San Pedro House also has an important educational component. We estimate over 1000 people visit the banding each year. We’ve had visitors from Japan that planned their trip around the banding study and people who have lived in Sierra Vista for years but had never visited the river discover the SPRNCA though our banding programs. Hopefully they come away from the presentation with a better understanding of hummingbirds, science and research and the fragile river that so much life depends on.

Tom Wood is co-founder of Southeastern Arizona Bird Observatory (SABO). He earned a degree in Wildlife Biology from Stephen F. Austin State University in Texas. Tom with his wife, Sheri Williamson, managed The Nature Conservancy’s Ramsey Canyon Preserve for 12 years before they founded SABO. He has contributed to a variety of conservation projects, including rare species research and ecotourism development in the Sierra Vista/Bisbee area and was involved in establishing the Southwest Wings Birding Festival. Tom is president of The Friends of the San Pedro River.