by Vicki Piaskowski, Kerry Scanlan and Steve Mahler
People who frequently watch birds look outside the windows of their homes and find a robin nesting in the same tree year after year. Many assume it is the same robin. How could one know if it is? Read on to learn about a technique used to identify birds as individuals.
To identify individual birds, bird banding was developed. The United States Geological Survey's Patuxent Wildlife Research Center has documented the history of bird banding:
"People have been banding (or ringing, as it is called in Europe) birds for centuries. The first record of a metal band attached to a bird's leg was about 1595 when one of Henry IV's banded peregrine falcons was lost in pursuit of a bustard in France. It showed up 24 hours later in Malta, about 1,350 miles away, averaging 56 mph!
Duke Ferdinand placed a silver band on a grey heron about 1669. The bird was recovered by his grandson about 1728, indicating the heron lived at least 60 years. In 1710 in Germany, a falconer captured a grey heron with several rings on one leg. The bander was unknown, but one of the rings was apparently placed on the heron in Turkey, more than 1,200 miles to the east.
The first records of banding in North America are those of John James Audubon, the famous American naturalist and painter. In 1803 he tied silver cords to the legs of a brood of phoebes near Philadelphia and was able to identify two of the nestlings when they returned to the neighborhood the following year." 1
In the early 1900s, scientific bird banding with numbered metal bands was developed and also included the collection and storage of banding data. In 1920, the U.S. Department of Agriculture took over the banding scheme. In 1923 the Canadian government began to administer all bands used in Canada. Since that time, the U.S. and Canadian governments have worked together, and bands are now standardized throughout North America. Now, the U.S. Geological Survey Bird Banding Laboratory (USGS BBL) and the Canadian Wildlife Service are responsible for overseeing all banding done on North American birds. In countries outside North America, the government generally regulates bird banding. For example, in Belize, Central America, a Scientific Research permit must be obtained from the Ministry of Natural Resources, Forestry Department, Conservation Division in order to band birds.
WHAT IS REQUIRED TO BECOME A BANDER?
The USGS Patuxent Wildlife Research Center has information on the steps necessary to become a licensed bird bander:
"Because banding birds requires capturing the birds and handling them before the banding takes place, the banding of birds in the United States is controlled under the Migratory Bird Treaty Act and requires a federal banding permit. Some states require a state permit as well. Only official federal bands may be legally placed on birds that are released to the wild within the US."
Bird banding requires specialized training and a permit and does not harm the birds in any way. To band North American migratory birds outside of the US or Canada, the bander is required to have both a federal banding permit and a permit from the country in which the migratory birds are being banded. For example, in order to band migratory birds during the non-breeding season (Wisconsin's winter) in Belize, Central America, the Zoological Society of Milwaukee Birds Without Borders-Aves Sin Fronteras researchers must have both a master permit from the USGS Bird Banding Laboratory and a Scientific/Research permit from the Belize government.
"Banders are a select group. There are currently only 2,000 master banding permits and 2,000 sub-permits in the United States. Master banders may work in federal and state agencies, university research projects, bird observatories, or they may work as private individuals. Waterfowl are banded only by federal and state agencies. Private individuals normally are not allowed to band waterfowl, as the banding information is used to set harvest regulations." 2
WHAT IS BANDING?
Bird banding involves placing a numbered, aluminum "bracelet" on the tarsus (lower leg) of a bird, examining and taking measurements, and then releasing the bird. To capture songbirds for banding, bird banders use special nets called mist nets. Each bird is removed carefully from the nets, placed in a holding bag made of soft cloth, and then brought to a banding station located near the nets to be banded. On occasion, a researcher captures a bird that is already banded. When this occurs, the researcher takes down pertinent information and forwards it to the Bird Banding Laboratory, where they check the banding database to see where and when the bird originally was banded.
WHY WE BAND BIRDS
Banding has helped to solve many mysteries about birds, including migratory patterns, how long birds live, and their life histories. Banding provides valuable information on the condition, age and sex of the birds captured. It also allows researchers to determine the species and numbers of birds present in a given area and whether the bird is breeding in this area. Banding is an important tool used to study migration patterns. Banding allows researchers to learn where a bird goes when it migrates and if it comes back to the same area the following year.
THE STEP-BY-STEP PROCESS OF HOW A BIRD IS BANDED
Now, imagine you are a well-trained researcher with a banding permit and that you are about to band a bird. You are on your rounds, checking your mist nets, and have found a bird in a net. You carefully remove the bird from the net and put it head down into a soft cloth bag to carry it back to the banding station.
Back at the station, you hang the bags from a hanger or from clothespins strung on a clothesline. Birds stay in their bags until you are ready to band them. Here are the steps you will take:
- HOLDING TECHNIQUE
Holding a live bird properly is very important; you use the bird bander's grip. It is important that you hold the bird firmly but not too tightly because you could damage the bird's internal organs. Some birds do try to escape by wriggling around, some peck at whatever is near, some kick, some are very loud and some defecate. Most birds, however, wait calmly while being banded and measured.
You use a leg gauge to measure the bird's leg so that you band the bird with the appropriate size band. (If you use a band that's too large, it could slide up over the "knee" joint or slide down over its foot, preventing the bird from closing its foot properly. If the band is too tight, you could prevent necessary circulation.)
Once you find the right band size, you carefully pry the band open with a special banding pliers, slide it onto the bird's leg, then close the band with the banding pliers. The special banding pliers maintains the circular shape of the band and prevents it from overlapping. You read aloud the number on the band, so that the data recorder can write it on the banding data sheet. (Each band number is different because each bird is unique.) The banding data sheet has many columns so the data recorder can write a large amount of information all on one line.
After banding the bird, you will try to learn as much as possible about the bird, within a 1¸- to 2-minute time span.
- FAT MEASUREMENT
The first measurement you take will tell you how much fat the bird has stored. Fat looks yellow and can be seen under the skin when you gently blow on the feathers of the throat and upper breast, stomach and underwing. The stored fat looks like the yellow fat you see in a chicken. As a researcher, you decide how much fat the bird has stored, tell the data recorder the fat code and the recorder writes it in the fat column of the data sheet. The lowest fat code is 0 (no fat) and the highest is a seven (yellow fat bulging in the bird's throat, stomach and under its wings). Birds with fat codes of seven are nicknamed butterballs! When migratory birds have a lot of stored fat, we as researchers know that they have stored fat for fuel and are ready to migrate.
- BODY AND FLIGHT FEATHER MOLT
When you blow on the feathers to check for fat, you also look for body and flight feather molt. You then also lightly blow over the rest of the bird's body and its wings to see if it is growing new feathers. By doing this, you can determine how old the bird is and the species molt patterns. You tell the data recorder the amount of molt. When a bird molts, it grows new feathers.
The next step is called skulling. Baby birds, like human babies, have "soft spots" on their heads when very young. A "soft spot" is a place on the top of the head where the skull plates have not fully developed. To check for a soft spot, you wet the bird's head with a couple of drops of water and then part the feathers to see the color of the skull. In a very young bird, there is one layer of bone causing the skull to look pinkish. As the bird grows, a second layer of bone forms and white spots appear, which are actually pillars of bone connecting the two layers of the skull. A skull with these two layers of bone looks whitish. When a bird's skull is fully formed, you know it is an older bird. Bird skulls are graded on a scale of 0 to 7. You tell the data recorder the bird's skull grade.
- WING LENGTH
Now, you measure the wing length with a special wing ruler. Wing length can, in some species, help you determine the sex of the bird. It also can be used to confirm the species. After measuring the wing length, you tell the measurement to the recorder.
- BODY WEIGHT
Finally, you weigh the bird. The weight of a bird can vary depending on the time of day, food availability and whether the bird is feeding or migrating. Before any bird is weighed, the scale is zeroed (tared) to account for the weight of the weighing tube. Then you place the bird head down in the tube, place the tube on the scale and read the weight aloud to the data recorder. There are several weighing tube sizes at banding stations to accommodate the different sizes of birds.
- RELEASING THE BIRD
After all of the data have been recorded, it is time to release the bird. You carry the bird in the weighing tube outdoors to a release box that is placed near vegetative cover. You gently slide the bird out of the weighing tube onto soft material on the bottom of the release box. Usually the bird flies away immediately, but in some cases it will sit and rest for a few seconds. The sides of the release box are 12 to 18 inches high. To clear the box, the bird must be able to fly well enough that you know it will navigate safely back in the wild.
Keep in mind that all of the above banding and measurements are done in 1 ½ to 2 minutes. The birds are held a very short time to minimize stress and allow them to return quickly to feeding or whatever activity they were doing when they were captured.
Capturing a bird allows the researcher to determine that the bird species is present at the research site. This is important, because often birds are not seen or heard, especially during fall migration. Recapturing a bird can provide information on how long birds live, how favorable the food supply is in an area during migration, and when birds are ready to breed. Furthermore, migratory routes and stopover sites can be determined.
USING TECHNOLOGY TO AID RESEARCH
Recent research includes the use of radio and satellite transmitters and global positioning systems to record the movements of large birds such as peregrine falcons. Bird banding, however, still is the most cost-effective and widely used method of learning about songbirds.
1 U.S. Geological Survey, Biological Resources Division, Patuxent Wildlife Research Center. (2000). Brief History of Bird Banding. Bird Banding Laboratory, The North American Bird Banding Program. http://www.pwrc.usgs.gov/bbl/homepage/history.htm (12 Dec. 2000).
2 U.S. Geological Survey, Biological Resources Division, Patuxent Wildlife Research Center. (2000). Who Bands Birds? Bird Banding Laboratory, The North American Bird Banding Program. http://www.pwrc.usgs.gov/bbl/homepage/whocan.htm (12 Dec. 2000).
McCracken, J., L. Enright, D. Shepherd, J. Cappelman and E. Dunn. 1999. Canadian Bird Bander's Training Manual. Technical Report # 275, Bird Banding Office, Canadian Wildlife Service, Hull, Quebec.
Pyle, P. 1997. Identification Guide to North American Birds. Slate Creek Press, Bolinas, CA.
Smith, H., J. McCracken and D. Shepherd. 1997. The Bander's Safety Handbook. Institute for Bird Populations, Point Reyes, CA.
Vicki Piaskowski (field experience).