There is so much we don’t know about wild birds, their behaviors, their migration patterns, and their relationships with each other and their environment. And no matter how in-depth we may study these feathered creatures from a distance, it seems like we are continually surprised. Since birds are relatively easy to observe, they are well-known by science in comparison to the rest of the world’s wildlife, yet many mysteries remain.
One way of tackling the hidden world of birds, aside from watching them, is to mark and monitor individuals. If we can safely catch an individual bird, we can attach a record to that individual and mark that bird with a unique identifier: a bird band. Bird bands are rings that are affixed to a bird’s leg and are typically made of aluminum or other metal with an engraved identification number.
I first began bird banding in 2006, when I volunteered with the Biocore Prairie Bird Observatory located at the University of Wisconsin – Madison campus. I have been leading bird banding stations and demonstrations ever since then and most recently, I led a bird banding demonstration at the Indiana Dunes Birding Festival in May 2022. Bird banding demonstrations help us explain to the public what we can learn from this research technique, while simultaneously contributing valuable data to the US Geological Survey’s (USGS) Bird Banding Lab, which compiles of all bird banding data across the country.
All bird banders must receive permits from the USGS as well as the state they are operating in to ensure bird banders are qualified and follow protocols to ensure the safety of the birds. Bird banders use many techniques in order to safely capture birds, but the most common technique is by using fine mesh “mist nets” strung between two poles.
What can we learn from bird banding or “ringing” as it’s called in Europe?
If a bird is banded and later recaptured, we can learn about the maximum lifespan for that species. The longest-lived bird is Wisdom, the Laysan Albatross, who is at least 70 years old. Songbirds don't live quite as long as albatrosses, but my own experience with a long-lived bird was a Yellow Warbler that I once banded at Horicon Marsh National Wildlife Refuge in 2014. The individual was later recaptured by another bander at Horicon in 2019 and was determined to be at least 7 years old at the time.
When we catch birds for the first time, we can often only tell if they hatched that year, hatched the previous year, are at least a year old, or at least two years old. For some species you may be able to determine that the bird is at least three years or four years old. Assessing a bird’s age depends on the species, but the clues are often revealed by the amount of wear on the feathers. Feathers lose their luster over time, which is why birds molt to replace them. A juvenile bird’s feathers often wear out sooner than an adult’s and the pattern of feather replacement (when a bird molts) can help clue us in on the bird’s age.
We can also determine a bird’s sex by looking at breeding characteristics that may or may not be apparent by watching a bird through binoculars. For some birds, their sex can be determined by obvious plumage differences, but for others we look for development of a “brood patch,” or a build-up of fluid beneath the belly skin used to incubate young or a “cloacal protuberance,” which is the visible growth of the male testes, to determine sex with a bird in the hand.
Individually marking a bird won’t tell us where it goes, that depends on a bird being “resighted” or “recaptured.” But increasingly, scientists use special kinds of technology to track bird movements that can be used in combination with bird banding techniques. At Audubon Great Lakes, our Conservation Science team deployed special radio transmitters called NanoTags on juvenile Black Terns in Michigan. These transmitters communicate with radio towers as part of the Motus Tracking System and can tell us if they’ve officially “fledged the nest” and where they’ve traveled to on their fall migration.
Scientists have studied the movements over 200 species of birds using NanoTags and other radio tracking technology.
A simplified version of tracking a bird’s movement is through the use of color bands. By giving a bird a unique combination of colored bands that can be seen from a distance, this gives us the opportunity to identify a bird without having to recapture them. An example of color banded birds is the Great Lakes population of Piping Plovers. The Great Lakes Piping Plover Conservation team uses color bands to identify individuals and find out where they overwinter, and if they return to the same breeding site year after year. Plovers with orange flags or orange bands without a flag are from the Great Lakes population.
Long-term Patterns and Trends
Banding year after year at the same location can provide us with trends about bird populations are doing locally and can also hint at larger population trends. A study run by the Institute for Bird Populations (IBP) called Monitoring Avian Productivity & Survivorship (MAPS) uses data collected at multiple stations across North America during the breeding season. Since each station operates under the same protocol, this helps scientists learn about topics such as demographic rates and timing of molts while comparing how these may vary by location. IBP also runs a companion project called MoSI (Monitoreo de Sobrevivencia Invernal) which studies North American birds on their tropical wintering grounds.
The Midwest Migration Network (MMN) and the Black Swamp Bird Observatory (BSBO) in Ohio developed a similar program that only studies birds during migration, called the MMN Banding and Ground Surveys Initiative. By running a bird banding station either daily or periodically during the migratory period, we can learn about demographics of migrating birds and how those may change by season or location. We can also study how birds accumulate fat during migration, which can be visibly assessed by checking for fat deposits just below the skin. Stations that operate over a long-term may also be able to measure how the timing of migration is changing over time.
With birds in the hand, we can take a number of physical measurements. These measurements can also cue us in on how bird sizes may be changing over time. Researchers are already finding indications that bird sizes may be changing in response to climate change.
Through all this data collection, bird banders can help us better understand bird populations and also interpret important cues to how birds are responding to their environments. Protecting bird populations is vital to enhancing our ecosystems as birds serve as pollinators, insect and rodent control, and seed dispersers. Birds also serve as excellent indicators of environmental health because they are sensitive to habitat change.
Banding allows bird populations to be more efficiently monitored, enabling researchers to identify areas where populations may be in decline and determine how and where we can respond to threats.
To learn more about where bird banding is occurring near you, you can consult a list of observatories here: https://birdnet.org/info-for-ornithologists/observatories/
To report a sighting of a banded bird, go to https://www.reportband.gov/.