Bands used on cactus wrens and burrowing owls, far left is aluminum wren band, middle are wren color bands, far right is alphanumeric band for owls.
Bird banding is an important tool for researching wild birds, allowing them to be individually identifiable in the hand or by sight. This can be especially important for birds that are too small to carry tracking devices such as radio collars or GPS tags. Both conservation research projects that I work on involve understanding some aspect of the population dynamics of birds that are too small to put transmitters on: coastal cactus wrens and western burrowing owls. An alternative method of distinguishing individual birds is to mark them with color or alphanumeric bands, in addition to standard aluminum bands from the US government, which are required for all banded birds and have a unique ID number.
This cactus wren sports a unique color band combination.
To mark cactus wrens, we use plastic bands that come in several different colors and also have our US government aluminum bands dyed green so as to distinguish them from bands used by other organizations also conducting research on cactus wrens in southern California. Each wren gets two bands on each leg (two plastic on one leg, one plastic and one aluminum on the other), giving us lots of combinations to work with so that each wren has a unique color combination. In the field, we use binoculars, spotting scopes, and photographs to identify individual birds. Because we know where and when each bird was banded, we can get a sense of how long the birds live, how far they move, and how they interact with each other.
Federal and state governments both require researchers to have a permit to band birds, and obtaining one can be a lengthy process because it involves gaining a lot of experience with bird handling and capture techniques. Throughout my academic and professional career, I have been involved with capturing and banding many different species of birds, but only at a trainee/apprentice level. Recently, I took a class in bird banding through University of California, Riverside, Extension to gain additional experience with mist netting and banding of small passerines (songbirds).
A Gambel’s white-crowned sparrow is caught in a mist net.
Mist netting is a commonly used technique for capturing songbirds; mist nets are made of very fine material that is difficult to see when set up properly. They are usually set up in high flight traffic areas (e.g. between trees or shrubs), and when the birds fly into them, they are caught in a pocket and become slightly tangled. The nets must be checked often or watched from an inconspicuous location so birds can be removed in a timely manner. Although we already use mist nests to capture cactus wrens, taking the class allowed me to gain a lot of additional practice in extracting birds from the nets. We also had the opportunity to work with many different bird species that we don’t usually catch.
After a bird was captured, we identified its species, banded it, determined its age and sex, and took standard morphometric measurements. Determining the age of birds can be very difficult, and in many cases you can only say that a bird is a juvenile of that year (a hatch-year bird) or an adult (an after-hatch-year bird). We learned how different feather wear and molt patterns can be used to determine the ages of the birds we caught. We also assessed body condition by looking at fat deposits on the breast and hips (birds have very thin skin, so it is easy to see the fat layer just below the skin). Over the course of the weekend, we captured and banded almost 300 birds! We also recaptured birds that were banded in the past and recorded their band numbers. All of the data collected will be given to the Federal Bird Banding Lab (part of the US Geological Survey) and used to look at trends in bird populations across the country.
Steve Myers (instructor) bands and takes body metrics of lesser goldfinches.
This experience will help me in the permitting process and proved to be an invaluable opportunity to learn new skills and get lots of practice with banding and mist netting. I can’t wait to get out and put my new skills to use. Watch out, cactus wrens, here I come!
Colleen Wisinski is a senior research technician in the Applied Animal Ecology Division at the San Diego Zoo Institute for Conservation Research. Read her previous post, A Sense of Wonder for Wildlife.