On Saturday, May 25th, NJ Division of Fish and Wildlife eagle project staff visited the eagle nest at Duke Farms to band the two nestlings. Normally banding is scheduled for the time period when the nestlings are 6 weeks old. Staff scheduled this visit for precisely the 8 week age because that is the ideal time for attaching a transmitter: the nestlings are nearly full grown, but not quite ready to walk branches leading off the nest. The webcam allowed biologists to time this visit exactly. However, the nestlings at 8 weeks of age are quite large and the climber’s experience definitely was important.
The nestlings were handled one at a time, hooded to keep them calm, and lowered to the ground in a canvas duffle bag. On the ground, biologists took measurements and banded them: E/87 is the female nestling, first-hatched and already larger, because even at this young age females are larger than males. The male nestling, E/88, measured as just one day younger (which, of course, we know because of the camera!), but his feathering was slightly more mature. Because males are slightly smaller, they are often ready for flight just a little sooner than females. Staff chose the male for the satellite transmitter because of his size and development.
The satellite tag is attached to a harness made of Teflon ribbon, used because its strength and smooth feel against the body. A bird can wear this for many years with no negative effects; in fact, an eagle that had worn a backpack transmitter for 18 years was treated at Tri-State Bird Rescue in Delaware, and there was no sign of any wear on the skin. The harness was fit precisely following guidance established by eagle researchers; the same kind of tag and harness has been used for a decade in Chesapeake Bay and elsewhere on over 300 eagles.
The technology of satellite tags has been developing rapidly, and now these tags are used to record millions of data points each day. Our tag will be recording E/88’s location daily and once at night, to identify the habitats that he (and other eagles) use and rely on. The nighttime locations are important to identify roosts that may be important for larger, regional, eagle populations. Often these roosts are “communal roosts,” which support 10, 40, or even 80 bald eagles. Identifying and protecting these roost locations is important for the future of New Jersey’s eagle population.
We hope that E/88 will go on to not only thrive in NJ, but also provide information that may help preserve critical habitat for generations of eagles.
Duke Farm Eagle Cam Transmitter FAQs
What is the data used for?
Data is used to learn about habitat use by non-breeding, sub-adult eagles as they move around for the first five years of life. The recorded locations each day will be used with other eagles’ data to provide information on habitats and potential threats. Data on critical habitats is considered by the NJDEP in the course of development permit review, long term planning, land acquisition, and projects that could conflict with eagles such as wind turbine siting. Overnight locations help biologists identify sites that could be communal roosts, which are worthy of long term protection to benefit the regional eagle population.
Why can’t wildlife just be left alone? Why do we need to track them?
Unfortunately, due to human interference over many decades, eagles need our help. Regulatory protection for healthy land and water is important, but knowing the health of our eagle population and being able to identify problems is a necessary part of being responsive and adaptive. The Duke Farms eagle nest is part of a huge success story, but there was a lot of hands-on work along the way. To learn more about work to recover the bald eagle, go to: http://www.conservewildlifenj.org/protecting/projects/baldeagle/
How much does the transmitter weigh?
The satellite tag weighs 70 grams, which is about 2% of an eagle’s weight. The USGS Bird Banding Lab has a guideline allowing a tag to weigh 3% of a bird’s weight.
Will the transmitter be on for its entire life?
The tag has a lifespan of approximately 5 years. The harness’s weak spot is the attachment knot, which should last for the 5 year period.
Does it bother the eagle?
We have the luxury of the webcam, so we can watch how the eagles react to the leg bands (on both birds) and the sat tag on E/88. In the first few days there seemed to be no reaction at all to the “bling.” In other species on webcam, such as peregrine falcons, they seem to give no attention to leg bands or transmitter attachments.
Will the straps get caught in a tree on a limb or something?
The harness for the transmitter was carefully designed and fitted so that it does not interfere with the eagle’s movements at all.
Do the parents notice something different?
The adults most likely notice the transmitter, but because it doesn’t pose a threat to them or the young, they aren’t alarmed by it. After attaching a transmitter to a chick the adults have always come back to the nest and shown normal behavior.
Does the reflective nature of the solar panel annoy the parents or make it a target?
This type of tag and harness has been used successfully on hundreds of bald and golden eagles. It is low-profile and is carried for years with no ill effects.
What were the stats from the eagle banding?
Banding Stats May 25th, 2019
Federal Band 0709-06527 (right leg)
State band- E/87 (left leg)
Culmen Length (mm) 49.6
Bill Depth(mm)- 31.9
8th Primary(mm)- 258
Tarsus(mm) avg- 15.55
Hallux Claw (mm)- 36.8
Weight (kg)- 4.46
Federal Band 0709-06528 (left leg)
State band-E/88 (right)
Culmen Length(mm)- 44.15
Bill Depth(mm)- 30.7
8th Primary (mm)- 254
Tarsus (mm) avg- 13.13
Hallux Claw (mm)- 33.85
Weight (kg)- 2.87