Bird Banding Technology Part 2

Modern Bird Banding

Hand tying silver wire onto a bird’s leg by John James Audubon in the 1700’s evolved to become today’s factory manufactured rings shaped from various kinds of metal or molded polymers, stamped with letters and numbers. With a reliable way of identifying individual birds established through the centuries, banding, or ‘ringing’ as it is called in Europe, evolved with the industrial revolution. New banding tools were invented out of necessity to band different bird legs, so as not to constrict and harm the bird's leg. Plastic polymer leg bands were also created where a tool would not be required. These bands are produced as a coiled plastic band resembling a child’s slap-on bracelet toy.

Molded polymer bird bands are typically made out of celluloid and Reoplex® (Poly 1,3-butylene adipate), as well as polyvinyl chloride or Darvic. These materials are light enough where they will not impede a birds flight or foraging habits. Since a typical passerine or songbird only weighs 15 to 30 grams, or 0.5 to 1 ounce, a plastic bird band weighing around .01 ounces, or 0.3 grams overall, might not have any negative effects on a bird wearing it. For example, a cardinal weighs approximately 44 grams or up to 2.0 ounces and a black-capped chickadee weighs approximately 9 to 14 grams. Also, to accommodate different sized birds, there are over 30 different standard sizes of bands that can accommodate the leg of a hummingbird to a bald eagle or trumpeter swan and they can range in widths from 2 mm to 27 mm.

As mentioned, bird bands can be made from various polymers or metals, such as aluminum, and can come in a myriad of colors. Aluminum bands that have different colors use an electrochemical process of anodizing the aluminum surface, so a secondary process of adding a coloring or corrosive preventing component can integrate onto the aluminum substrate. Smaller bands, made with metals or polymers, typically have butt ends and are usually imprinted with letters, numbers, symbols, and even country codes for distinguishing birds of the same species. Different organizations, state agencies and environmental research groups will use multiple bands on the same bird using different colors and combinations of aluminum and plastic bands to distinguish where the bird was banded and who is doing the banding.

Determining the type of band to use on a specific species of bird is based on how long a particular bird lives and in what environment the bird typically inhabits. Does it frequent a fresh water lake or river or does it forage and breed in a more corrosive environment, such as a salt water marsh? Metal and polymer bird bands have a life expectancy as well. Materials degrade and wear out after prolonged exposure to the elements, so choosing the appropriate band for a bird requires some knowledge of the bird’s habits.

Smaller birds such as terrestrial songbirds and hummingbirds, that typically have a shorter lifespan (~2 to 8 years) and may have exposure to freshwater such as rain or the occasional backyard bird bath visit, only require a band made of plastic or aluminum. Larger birds such as ospreys and bald eagles, which can live up to and beyond 30+ years and in many cases encounter salt water habitats, require a metal band that is more resilient to the environment. To serve this purpose, bands made from stainless steel, aluminum, copper, Monel, or incoloy (a type of superalloy) are typically more expensive, but have a much longer lifespan and usually are made with a robust fastening feature such as a lock-on rivet. These bands are ideal for larger birds requiring resiliency and longevity. The hardier metals deter these large raptors from removing the band with their strong bills. Lock-on riveted bands are usually attached using a device called a ‘pop-rivet gun’ developed by Charles Sindelar, an ornithology professor formerly at the University of Wisconsin.

Although bands are typically attached around a bird’s leg, there are other variations of aluminum and plastic polymer bands created for different sized birds. For larger marsh birds and waterfowl, such as geese and herons that have long necks, non-heat conducting, expandable and flexible vinyl neck collars are used. These neck bands will allow a long-legged wading bird to move through a marshy area without a band on its legs catching on debris.

Other waterfowl such as the common loon have thin, almost rectangular legs. These birds require a specially made flattened band that looks like a squashed ring, and that will fit comfortably on the bird’s leg, allowing it to paddle unencumbered.

Bird banding has been used for over 100 years and continues to be used as an inexpensive means of tracking a bird, but it does have limitations. The banded birds must be either observed or re-caught to be able to identify the banding code on the band or ring. There is mortality as well and not all birds are re-seen or recaptured.

In part three of this series, we’ll look at another technology that was developed and being used to better track where birds go – electronic transmitters.

Image credit: Júlio Reis/CC BY-SA 2.5

Previous Blog Entries in This Series:

Bird Tracking Technology - A Little History (Part 1)