Q: How is the transmitter attached to the bird?
A: GPS transmitters are fitted on eagles with Teflon straps – much like how a human would wear a backpack.
Q: Won’t the transmitter weigh the eagle down?
A: No, the transmitter is very light and weighs only about 80 grams. In general, when transmitters are fitted onto eagles and other large birds, it is recommended that the weight of the backpack not exceed three percent of the bird’s body weight. In this particular case, the transmitter is two percent of the bird’s body weight.
Q: Will the transmitter fall off after two years?
A: This transmitter is permanent and will either stay on for the lifespan of the bird or will be taken off if the battery is dead and the bird is ever caught.
When the GPS transmitter is placed on a bird, the vital part of the fitting that secures the backpack in place is the piece of line that holds the two straps together. While cotton string can be used, the biologists working with the Wildlife Center in this case prefer working with an alternative material. West Virginia University Professor and Cellular Tracking Technology biologist Dr. Todd Katzner prefers using a stronger woven line that won’t break down. Dr. Katzner, who has been attaching transmitters to birds for over 15 years feels that this option is safer for the birds in the long run because it is unlikely to partially fall off, leaving a dangling strap that could entangle the bird.
Generally speaking, the tear-away variety are used when researches want to recover the transmitters.
Q: How does the transmitter work?
A: These types of transmitters use satellites to record GPS information. By using a cellular network to transmit data, the transmitters are able to provide GPS points every 15 minutes. Data is temporarily unavailable when the birds fitted with these units fly out of cell phone range, but all information is stored and readily available once the bird is back in range.
In this particular case, there is great cell coverage up and down the Eastern Seaboard so we’ll likely be able to receive consistent data. This transmitter is designed to send data every other day.
Q: How often will we be able to see where the eagle is?
A: Once the bird is released, we should be able to receive a data update every 48 hours, which will report the eagle's movements. A standard time will be set on the transmitter so that data comes in at the same time each day. However, receiving the data also depends on if the bird is “in-range” at the check-in time.
For example, if the transmitter is set for a data download at 3:00 pm EST – we will receive that information at 3:00 p.m. every other day. However, if the bird flies out of cell phone range on a transmitting day from 2:55 p.m. to 3:05 p.m., the data will not be received that day. It will be stored, however, so that if the eagle is back in range the two days later, all movements can be tracked.
Please bear in mind that the WCV will be checking in to the tracking system to receive the data – and we will have to upload the data and maps to our website. Because there is a human working on providing this information, we will not be able to upload maps every day to the website. We should be able to provide updates once or twice a week.
Q: How long will the transmitter last?
A: These types of transmitters have lithium batteries but also are adapted with solar chargers. They have a lifespan of about two years.
Q: What do we hope to learn from the information?
A: For the Wildlife Center, this is a fantastic opportunity for a post-release study on one of our rehabilitated raptors. There have been very few studies done in this area. We look forward to watching the movements and behaviors of a bird that has been at our facility.
We’ll also be contributing information to an ongoing research study. As noted above, DGIF Biologist Jeff Cooper has fitted many Bald Eagles with GPS transmitters in the past few years – in total, 90 Bald Eagles will receive transmitters in this study [30 nestlings, 30 sub-adults, and 30 adults]. This study looks at the data received from these Bald Eagles to determine the range and behavior of Bald Eagles in Virginia’s coastal plain. Migratory behavior is studied as biologists are able to see how far Bald Eagles move in the winter season. The data is also used to discover communal roost sites of Bald Eagles.
Additionally, the data will play an important role in modeling how these birds use airspace. By looking at heights at which the eagles fly, average distances, and other specifics, biologists are able to relate this eagle behavior to real-life issues, such as airstrike data.