Bird Watching: The Science of Banding Can Take Many Different Colors


A grieving warbler rests as a researcher gently ties an identification band around its leg. Jack Milton / Personal Photographer

In the last column, I described the techniques used by bird banders to safely capture and equip birds with uniquely numbered aluminum rings. The Bird Banding Lab, a federal office, serves as the central repository for all banded birds. The data include all recaptures or recoveries of banded birds.

The first bird banding known to us was done by John James Audubon in eastern Pennsylvania. He tied aluminum wire to nesting Eastern phoebes and found that the birds returned the following year to nest. By tagging the birds, he was able to demonstrate that these birds are loyal to their nesting sites over the years.

Of course, the power of modern bird banding depends on whether the banded birds are then captured or found dead so that the ring number can be read. Knowing when the bird was banded provides information about the bird’s spatial movement as well as its minimum age.

The success of any banding program depends on how quickly the banded birds are found. The chances of capturing a banded bird are obviously greater for resident birds. For migratory birds like shorebirds, warblers and many other birds, few banded birds will be found. But there are thousands of banded birds, so at least a few are then encountered by banders elsewhere.

For larger birds like geese or eagles, the ring number can often be read directly with a spotting scope, so these birds do not need to be recaptured to identify the individual.

Many banders now place colored rings, in addition to the required aluminum rings, on captured birds. Color banding requires special permission from the Bird Banding Lab to ensure that banders in the same area do not duplicate banding combinations. By using a unique combination of color bands for each bird, one can identify individual birds without having to recapture them to read the band number. I used this technique to study variation in feeder attendance among black-capped chickadees and to estimate the length of stopover for western sandpipers in Washington state.

The Pan American Shorebird Program has established a valuable protocol followed by shorebird banders in North America. Banders equip captured birds with a standard numbered aluminum ring and plastic colored ring with an extension perpendicular to the shorebird’s leg. These elongated bands are rightly called flags. Each region of the Americas has a unique color. Banders use white flags in Canada, green flags in the United States, gray flags in Central America, pink flags in the Caribbean, etc.

The extension on the colored band makes the flag easy to see through a telescope. The specific identity of a shorebird that is tagged without capturing it is not known, but if you see a shorebird with a red flag, you know it has been banded in Chile. This is valuable information.

The millions of banding records and the thousands of recapture records are available to interested researchers. This database has been a boon for my studies of outbreaks of finches and red-breasted nuthatches.

Here are some of the ornithological discoveries made possible by bird banding. Findings of ringed Arctic terns show that they migrate from pole to pole, twice a year.

By tracking the disappearance of resident banded birds (likely because they died), we know that many resident songbirds have a 50% chance of dying each year. So how about a tit banded in Minnesota that was recaptured 11.5 years later! This is old age for a species where few even live to see a fourth birthday.

We learned a lot about the wintering grounds of different bird populations. For example, the palm warbler performs an interesting interbreeding during migration. Populations breeding in the upper Midwest and Prairie Provinces of Canada migrate southeast to winter in Florida, while our Eastern Warblers migrate southwest to winter along the Gulf Coast.

Herb Wilson has taught ornithology and other biology courses at Colby College. It welcomes comments and questions from readers on [email protected]

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