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Peter McKenzie-Brown is a Calgary-based writer, author and historian.

If you live in southern Canada, from the Atlantic provinces to the Rockies, you have likely seen a ruby-throated hummingbird. Beautiful but solitary, they breed in the North.

In autumn, they migrate south. Most end their journeys when they reach the Gulf of Mexico, but some fly across the Gulf of Mexico to the Yucatan Peninsula – 800 kilometres flown with three-gram bodies. Though Canada-born, they make instinctive beelines to their winter homes. Summer and winter, many return to the same gardens year after year. We know because bands on their tiny legs enable us to track their passage. Those bands have become vital tools for ornithology.

Dramatic reductions in the populations of bird species – the result of predation, farming and forestry practices – are the backstory to our efforts. In the Calgary area, for example, bird loss led to the formation of a registered society that sponsors the banding of mountain bluebirds and tree swallows. During the summer breeding season, my friend Bill Taylor and I pull up to a nest box and obstruct its opening with a rag. He bands the nestlings if they are old enough, then continues to the next box.

If house sparrows have built a nest in one of the boxes, we unceremoniously remove it. That species is invasive, unlike house wrens, which are protected.

In autumn, we trap northern saw-whet owls at night with nylon or mesh mist nets, record their biometrics, band and release. All three species are small enough to hold in one hand.

Using purpose-made tools, Bill clips a band with a unique number on a captured bird’s leg. He later reports the date, place, species and number for this bird. During its lifetime, the chances are good the bird will be recaptured and reported to birding authorities. In this way, avian science can reconstruct its movements.

For the record, some bird markers are readable from a distance – neck collars for geese and swans, for instance, and wing markers for vultures, eagles, swans and herons.

Banding works because of the international machine in which each bander is a minuscule cog. If anyone recaptures a banded bird, or finds a band on a dead bird’s leg, that band tells how to report date and place – information to help ornithology better understand migration patterns and changes in behaviour over well-defined periods. The United States Geological Survey (USGS) staffers manage more than 77 million archived banding records, receiving some 1.2 million banding records and 100,000 encounter reports annually.

Now a worldwide phenomenon, the practice got a boost in 1918 when the U.S. and Canadian governments signed the Migratory Bird Treaty; two years later it became federal law.

To become a bander, you must have a government-issued permit; most of those with banding permits are ornithologists, biologists and wildlife technicians; the others are birders and environmentalists who just want to help.

With the help of planet Earth’s armies of banders, ornithologists long ago established that migratory birds need intact habitats to survive. Banding contributed to an Audubon Society report that says two-thirds of North American bird species are at risk of extinction.

Banders record the location, date, species, gender, estimated age and other information about the birds they band, and submit their data to the appropriate regulator. USGS works with the North American Banding Council to develop banding materials and address safety issues.

Banding enables science to better understand avian migration patterns and habitat, thereby identifying priority areas for conservation. Changes in the age of birds caught may indicate longer or shorter life expectancy. The number of annual captures may indicate whether populations are increasing or in decline. Weight and wingspan data can show health trends. Sampling wild birds for Lyme disease and avian influenza can help determine these diseases’ prevalence, and which human and animal communities may be at risk. Toxicologists can assess a species’ exposure to contaminants and other environmental threats.

Banding is by no means new. In 2020, a USGS article celebrated banding’s first century in North America, noting that birds contribute more than beauty to our planet. Many plants need birds to pollinate. Hawks and owls target rodents and other pests. Fruit- and grain-eating birds help spread the seeds of the plants they consume.

The Canadian bird-banding program in Ottawa issues permits to capture and band within Canada. Co-operatively run by Canada’s banding office and the American Bird Banding Laboratory, this program relies on the public to report sightings or recoveries of bird bands and other avian markers.

Because banders contribute greatly to our environment, there’s always room for more. Like humankind everywhere, banders are curious about the world around us. We study everything on this planet – from its molten core through to the biosphere and the reaches of space. We are, after all, a curious species.

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