What are PIT Tags: Passive Integrated Transponders?

Passive Integrated Transponders, or PIT tags, are tracking tags that do not require power. Instead, they have an internal microchip that is activated when it passes close to a special antenna. The antenna is connected to a computer that records the identity of the tag and the time that it passed by the antenna. A common example of this tag is the "E-ZPass" that you may have seen your parents use when driving on the highway. An EZ-Pass does not require power. The toll gates contain a giant antenna that talks to the tag to determine the identity of the car and to record what time it passes the gate.

PIT tags can be attached to birds in a number of ways. The most common way is to glue the tag to a band (a metal or plastic ring) that a bird carries on its legs. The tags can also be placed under a bird's skin or even injected into the bird using a small needle.

What are the pros and cons of using PIT tags?

PIT tags provide many advantages for researchers studying birds. The biggest advantage of this tag is that it does not need a battery, so it can last for the entire time that an animal is wearing it. Because these tags do not require batteries, they are also very light and can fit on birds of any size. These devices are also very inexpensive, with the each tag typically costing less than $2. This means that scientists can deploy a lot of tracking devices without spending a lot of money.

Though a PIT tag is great for exploring some aspects of bird behavior, its use is limited. The main drawback of this device is that is has to be very close to the antenna to transmit data—typically just a few inches to a few feet away. Scientists will not retrieve any data if the bird is outside of that distance. Therefore, these devices can only provide data at the location of the antenna.

Despite this drawback, with the correct antenna placement, scientists can learn a lot using PIT tags. By placing an antenna in a location where scientists expect a bird to go, they can determine many things. For example, by placing an antenna under a bird's nest, researchers can learn how often parents feed their young. By placing an antenna under a bird bath in an area without a natural source of water, researchers can determine how often a bird drinks or bathes.

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