Eagle Tracking Information
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Additional support provided by: ConocoPhillips, U.S. Fish and Wildlife Service, and individual donors.
"GROUND CONTROL TO MAJOR MOM"
LEARNING MORE ABOUT OKLAHOMA EAGLES THROUGH SATELLITE GPS TRACKING
We were concerned that the parent Bald Eagles in Sand Springs might not be able to find their three fledgling offspring once the youngsters left the nest, so we decided to put solar powered, satellite- tracked transmitters on two of the young birds. That way, the young eagles would always be "checking in" automatically so that the adults would know where their offspring had wandered, even if they had left the state. OK, we are pulling your leg about our reasons, but such a tracking device would certainly be the dream of many human parents. From studies with other raptors such as Peregrine Falcons, we know that the parent birds of prey (like other birds) have the ability to quickly locate their offspring after the latter have flown from the nest. The adult female's job is to guard the young birds once they are out of the nest, and to take food from the returning adult male for transfers to the young, that is, if the male does not carry it directly to the young on return from his hunting trip. Some of this searching is aided by begging for food by the fledglings, sometimes perched in inconspicuous, foliage-covered areas, when they see their parents flying in the area.
Our efforts are to learn more about where young Bald Eagles go and what they do after the eaglets fledge and disperse from some of the more than 120 nests in the Sooner State, and the Sutton Center has expanded our eagle nest cam project with support in part from NatureWorks. This study involves placing backpack-mounted, satellite transmitters on young eagles in the nest prior to first flight. These solar powered transmitters provide GPS (global positioning system) coordinates to five ARGOS satellites several times daily for the next 3 years or more, or as long as the eagles survive. (Only approximately 65% of first year birds of prey survive to be one year old.) Sutton Center biologists can log in on a weekly basis to retrieve these data that are collected and stored daily. Weighing some 60 grams, or a little over two ounces each, compared to about seven to 12 pounds for the eaglets depending on gender (females are larger in most birds of prey), the transmitters are light enough to be easily carried by the birds during flight. They are attached to the eaglets by Teflon ribbons that crisscross over the chest. The biggest problem is keeping each transmitter high enough off the back so that overlapping feathers do not cover the small, integrated solar panels that collect energy from the sun.
This solar powered transmitter will allow us to track the movements of
a young eagle for up to several years before it falls off.
During our first efforts with this type of satellite transmitter (produced by Northstar Products and Services of Baltimore), on May 26 of this year, we mounted one unit each on a young male and a young female Bald Eagle in a nest by the Arkansas River near Sand Springs, OK. They have a third nest mate, a male that we did not equip with a transmitter. (Unfortunately, the two eaglets in a small nest near Red Rocks, OK, where we had a camera mounted, fell out of the nest prematurely and perished, one at 2 days of age, and one about a month later; as a result, we were unable to put transmitters on those two eaglets as planned).
Alan Jenkins prepares a transmitter for use on an eagle.
To paraphrase as we casually mentioned above that "we mounted the transmitters on the eaglets" and "will collect information relayed via satellites" significantly simplifies what is/was required in order to accomplish this task. We thought that Sutton website viewers and eagle cam observers would be interested to see what is actually involved in order to obtain dispersal and migration data from these young eagles over the next few years.
First of all, Alan Jenkins, assistant director of the Sutton Center, has worked in coordination with USFWS during waterfowl surveys to fly with their pilot, as well as to survey independently by kayak, truck, and on foot over the last 20 years to annually check out reports statewide of Oklahoma Bald Eagle nests (which sometimes turn out to be Red-tailed Hawk nests instead). Because Alan has a catalog of nest locations developed over such an extensive period, we were able to spend just three days checking nests that Alan thought might be in "climbable" trees.
There are many things to consider when evaluating nest trees for a climb since most nests are 70-100 ft high, and climbs to these nests are obviously dangerous. These factors include the species of tree where the nest is located, and most of them are in big cottonwoods, one of the most brittle to climb. The configuration of the tree is also important. Whether the nest is in a vertical crotch, close to the main trunk (the safest), or whether it is on branches that lean out horizontally away from the main trunk makes a big difference in the danger factor. Cottonwoods easily split if the nest-holding branches are not vertical. And several of the nests are in dead cottonwoods that are the most dangerous of all. Plus, if they are covered with vines such as Virginia creeper or poison ivy, which can extend out three feet all the way around the trunk, it is hard to evaluate the condition of the wood in the trunk. Vine growth this heavy makes it impossible to flip the climbing belt upward as one plants the tree climbing spikes to take each step.
We made our last evaluation of several nest trees on a Friday, and all nests had well advanced young in them; but, it was hard to tell just how advanced some were from the ground since the nests hid much of the feather growth from our vision. We needed two days to get the equipment ready in preparation for the entire operation. When we returned to the first tree on the following Wednesday, the one young in it had already flown and actually appeared to have been capable of flying for several days once we saw it in the air. Two young in another nest both flew around in the general vicinity, as if they had been on the wing for a couple of weeks, and then suddenly made shallow dives and landed back in the nest. A third nest tree was so heavily covered with poison ivy and Virginia creeper that it was next to impossible to climb; in short, we were not going to use that tree even without vines, since the nest was on a pair of rather small horizontal branches and offered serious danger should a climber venture out on them.
Finally we came to a fourth nest that we had considered for camera use in past years, and that we thought was in a tree we might be able to climb. Again, it was a cottonwood, and the nest was only about 70 feet high. It had Virginia creeper vines covering much of the lower trunk, but not so thick that one could not make it up the trunk if determined and the first part could be skirted with a ladder. The bad part was that the branches that cradled the nest were primarily horizontal and only moderately thick, but it was our best bet. This nest was close to the river, and if the young jumped out of the nest when we climbed the tree, the birds might end up in the water. The current was swift so we would need help. And the vegetation below and around the nest tree was thick so that birds bailing out might be easily lost in the understory if we did not have assistants watching for them and immediately ready should the eaglets try to fly. Of course this advanced age is the best time to place the transmitters on the birds since they have to be almost fully grown in order for the backpack straps to be snug enough but still allow for full muscle development and proper fit into adulthood. As we continued to evaluate the nest, we discovered that there were three young in it. We had only seen two initially since the third had been lying down in the middle. It is impossible to see into an eight foot diameter nest from 70 feet below it, so it is easy for the contents of eagle nests to be undercounted during ground surveys.
This nest presented a daunting climb. Note archers
at the bottom left of photo.
Prior to all this, we had obtained the necessary federal permits to work with the eagles, and we had ordered and registered two backpack mounted, solar transmitters with the ARGOS satellite people months before. We had also removed the magnets that kept the signal transmission in the "off" position a few days prior, leaving them in the sun at our facility so that they could charge up and begin transmitting signals. Once they were turned on, we were able to confirm that they were working with help from the good folks at RadioShack who used special equipment to confirm that both transmitters were sending out signals. This is important because in rare cases, a magnetic switch can stick and the result is a non-functioning transmitter on a flying bird without giving back a signal. Now that is a real bummer, and an expensive one at that!
We had arisen early on Wednesday morning so that we could meet at the Sutton Center in Bartlesville by 6:00 and head down to the Sand Springs nest. It was going to be a hot day, and we wanted to make the climb before the winds came up and before it got too warm for the eaglets. After loading our little bass boat and trolling motor, and Alan and Sally Jenkins' two kayaks, along with a 30 ft extension ladder on our 16 ft trailer, we headed out with a crew of six people. We first applied plenty of chigger, mosquito, and tick spray, but we failed to dose up with poison ivy prevention balm, something some of us would later regret.
Once there, we drove close to the bottom of the nest pulling the trailer and boats, and Dr. Lena Larsson, our post-doc, along with Alan Jenkins and Ryan Van Zant placed a kayak off the 6 ft drop at the river's edge into the water so that Lena would be ready to paddle if the eaglets ended up in the water (eaglets can swim by rowing with their wings as they float on top of the water, but would need to be retrieved if they fell into the river). Then, our spotters, Jennifer Reeder and Elizabeth Maupin stationed themselves along the dike so they could see any eaglets if they tried to fly.
Next, while Jen held up a shade to keep the sun out of his eyes, Steve Sherrod shot an arrow over a fork 70 ft up and beside the nest while monofilament tied to the arrow was fed out from an open faced fishing reel by Ryan VanZant. This took a few shots since the line broke twice. Finally Ryan and Jennifer were able to pull up a climbing rope with the fishing line so that Steve Sherrod, an aging (his word!) but experienced lifelong climber, would be able to attach to it and have a safety rope while climbing the trunk with tree spikes. Once to the top of the extension ladder, Sherrod grabbed the vines in order to plant his spikes in the trunk since the vine growth prohibited use of his safety belts. When above most vine growth, he was able to use the belts and progress up the tree with spikes to just below the nest while being belayed by Ryan. Upon approach to the nest, as Sherrod tied in to a branch for safety, the second oldest eagle chick, a male, jumped out of the nest and headed downward in a 45 degree angle into the underbrush. This is not an unusual occurrence during wildlife studies of this nature, and Alan Jenkins was in quick pursuit when the eaglet hit the ground running.
An arrow was used to get a climbing rope over a branch, while a ladder was used
to help get past part of the vine-covered trunk of the tree.
Steve Sherrod nears the nest using tree spikes
while "on belay" by Ryan VanZant on the ground for safety.
This young Bald Eagle prepares to make its first flight from the nest.
Alan returned with the chick so that the transmitter could be attached to the bird. Ryan Van Zant is experienced at applying backpack transmitters on falcons since he has helped with perhaps one hundred such units mounted with Teflon ribbons. Alan Jenkins has also mounted backpack transmitters on many of the ninety Bald Eagle chicks that were released in Oklahoma through the Sutton Center's reintroduction program some 20 years ago. It was this program that helped establish the parents and grandparents of the birds we were equipping with transmitters on this day. Mounting the backpack transmitters is critical because the tension on the Teflon ribbons has to be just right so that the birds can fly comfortably but yet the unit will not slip off. And, it is important that the chicks do not become overheated during the process, so they were sprayed down regularly with a mister bottle of water to provide evaporative cooling. The birds were hooded during the process to keep them calm and to reduce stress.
Lena Larsson grabs a nearly full grown eagle after it left the nest and
prior to installation of its transmitter.
Alan Jenkins, Ryan VanZant, and Jennifer Reeder work to install transmitters on two eagles.
The eagles are hooded to reduce stress, and are misted with water to cool them.
Gaining access around a huge nest is always a very difficult part of the climb. As Steve began to enter the nest, the oldest nestling, another male, launched off and began flying. The good part was that the bird was headed away from the river. It was his maiden voyage, and he struggled, but he did well. He swerved with rowing wings out over the spacious front lawn of a neighboring business, before he disappeared in a downward glide behind some trees. Jennifer Reeder and Elizabeth Maupin were in hot pursuit. With help from some of the business employees, the eaglet was located about 20 ft up in a pine tree. The employees furnished a ladder, and then a "cherry picker" lift to help Alan, Jen, and Elizabeth retrieve the bird from the pine tree and head back the couple of hundred yards to our location below the nest tree. We are grateful for this help from the employees of Fullerton Finish Systems, Inc. Shortly thereafter, the last and youngest chick, a female, bailed out and headed to the ground at a 45 degree angle. Lena was on it immediately, and Ryan helped her hood the bird. This female was then equipped with the other backpack unit and prepared to be returned to the nest. Mounting each transmitter takes about 30 minutes for proper fitting and application, but a slightly roomy, yet secure fit is one of the most important parts of the entire operation.
This hooded Bald Eagle is wearing its new
lightweight transmitter on its back.
Each hooded bird, with feet taped for safety to the bird and to the handler, was placed in a full zippered canvas duffle bag individually and raised back up to the climber before being removed, unhooded, untaped, and placed gently back in the nest. This is harder to do than one might think while holding onto branches in an effort to avoid falling from 70 feet up. Each bird was placed back where it came from, and they all stayed in the nest without trying to flee. Having banded several hundred young Bald Eagles, both in our release program and during graduate studies in the Aleutian Islands, we knew what to expect from birds of this age in the nest. Of course, the adults will and did return to continue taking care of the fledglings after our team exited the area. Having been in the tree for some four hours, Steve collected prey remains from the nest that included turtles and fish for later study, and rappelled from the nest to the ground. We loaded up our gear and headed back, tired, sweaty, and sporting some poison ivy, the presence of which would become more apparent within a few days.
Three young eagles all back in their nest. The two on the left are wearing
new transmitters, as can be seen by the visible antennas. We hope to
follow their movements for several years.
Prey remains collected from the eagle nest. A variety
of turtles and fish remains were present.
In the meantime, Dan Reinking had arranged with our website developer to prepare an application that would allow us to display the location data we receive from the satellite transmitters as the eaglets fledge and begin to move around the nest area. It is really more complicated than that since Dan and Lena have to decode the accurate GPS locations that are encoded in the data we receive that provides the less accurate Doppler location readings. Location data are collected and stored by the satellites several times per day, but because of the cost involved in retrieving the data, we only download it once per week in a large packet. The location data shown on our maps will therefore be at least one week behind real time. We anticipate that the young eagles will move similarly to those tracked through VHF transmitters by ground truck some 23 years ago by Alan Jenkins. Those two birds left our hack (release) sites during the heat of an Oklahoma summer, headed north toward Canada by July 4 and reached our northern border within about 11 days. We think they probably go there to seek out cooler weather and to utilize available food sources, but the adults appear to stay back here and defend their territories throughout the year. We will see if this proves to be true, as we hope we will be able to continue tracking this year's eaglets for several years.
We ask the patience of the viewers with this first attempt using satellite transmitter technology to share dispersal and migration information with you. As with the nest cam and loss of this year's chicks, not everything goes the way one might wish, but this is the way things happen in the natural world. Many young birds die in their first year, and technology can fail. Please keep your fingers crossed and send good karma, and we hope to learn more about how we can help manage Oklahoma Bald Eagle populations both in the Sooner state as well as during their travels elsewhere.