Tuesday, May 22, 2012

2012 Transmitter Decisions

The Raptor Resource Project has purchased a transmitter and will be attempting to put it on one of the Decorah juvenile eagles later this year, once they are on wing. We've attempted to answer some of the questions we've received regarding transmitters below.

Why are you doing this?
The eagles we attach transmitters to are part of a larger longitudinal study investigating and documenting the lives of Bald eagles. We are learning a great deal about Bald eagle travel, wintering, and even socialization. However, our eagles are extra special because we know their place of origin. The rest of the birds our eagle biologist traps are juveniles or adults wintering along the Mississippi river. We think they may be from Canada, but don't know that for sure: many of them nest in Canada in the summer. We know where our eagles come from and we know their life histories, so their behavior will help illuminate the life histories of Bald eagles in general. So far, we know that D1 has a pronounced affinity for rivers, seems to enjoy the company of other eagles, and makes long flights. She didn't winter much further south than her place of origin, returned to Decorah (if not the fish hatchery) a number of times, and traveled north in the summer. While eagles are often associated with large rivers and magnificent landscapes (stony crags, snow capped mountains, mile-wide river canyons), D1 spent a great deal of time on small river systems that may seem less significant to us, but were very important to her. The preservation of river systems, even small ones, are clearly important to the health and survivability of Bald eagles long term. We may think we know a great deal about Bald eagles, but D1 (and her future study mates) are teaching us how much remains to be learned. The transmitter is yielding data on a part of their lives - what Bob sometimes calls the wandering years - that could not be studied otherwise.
10 Days in the life of D1. This data was collected between January and February of 2012 and shows D1 on the Little Turkey in NE Iowa. To make your own D1 map, go to http://www.raptorresource.org/maps/personal.php

How do you know it doesn't bother the eagle? What about reproduction?
When we first started talking about putting a transmitter on one of the Decorah eagles, we did a lot of research and talked with an eagle biologist we knew. There are many ways transmitters can be attached to birds, and we wanted to make sure we used something with a good track record. Did it have a long history of use? Did the eagles studied have mortality rates significantly higher than what we know about Bald eagle mortality rates? Did eagles that died and were recovered show signs of damage or wear from the transmitter rig? Were we able to confirm that eagles wearing transmitters reproduced? In the end, we went with the backpack because it fit our criteria. Male and female eagles wearing it have been observed nesting and appear to live normal reproductive lives.

Can we say for sure that D1 or any other eagle isn't bothered at all by the transmitter? No, we can't. Shortly after D1 was fitted, she seemed to do a little extra preening around her shoulders, where the backpack straps were located. This soon ceased, however, indicating that any discomfort was short-lived. Her parents didn't reject her, her siblings didn't reject her, and other eagles haven't rejected her. She flew long distances and survived her first year, indicating that the backpack didn't impede flight, feeding, or travel. 

What kind of trap will you use to catch the juvie?
We'll most likely use a pan dam or noose trap again: a metal hoop with monofilament nooses that snare the eagle's legs.  This method has been used for centuries by Eastern falconers, since it is easy to build, easy to set, and quite safe.

We lure the eagle into the trap, which is roughly the size of a hula hoop, with a dead fish or two. As it comes into the trap, the snares entangle its legs. There are no snapping or moving parts to this trap: the trap mechanisms (snares) are passive, so they do not spring or slam shut. We don't want the eagle to fly away with the trap still attached, so we tether the trap with a strong springy cord, which serves as both a stopper and shock absorber if the eagle does try to fly away. We conceal ourselves nearby so we can get to the trap very quickly once it is caught.

Here is a video of last year's capture: http://www.iptv.org/iowaoutdoors/story.cfm/story/8612/iao_20110809_105_eagle/video

Who makes the transmitter? Was it custom-made for RRP?
The transmitter is made by North Star Science and Technology: http://www.northstarst.com/
It is a solar-powered PTT. We don't have a model number.

Some things are custom - for example, we directed how often the PTT should cycle on and off to conserve battery life while collecting the data we need, and used an appropriately-sized and weighted rig for a large bird like a bald eagle. Other things, like the design of the PTT itself, are standard in every case.

Here is a clip from last year of D1 with her transmitter on. We are using the same overall design this year.

Will you use short and long range transmitters?
We will. At this point, we are able to use one transmitter for both purposes, so the eagle will have one transmitter instead of two. Looking at the satellite data, it seems like it should be easy to find an eagle using long range only, but in our experience it is nearly impossible, especially when they are in heavy brush.

How much does the transmitter weigh?
The transmitter weighs 55 grams, which comes out to about 2 ounces. Iowa Bald eagles weigh roughly 8-12 pounds (we estimated 8-9 for Dad and 11-12 for Mom), so the transmitter weighs about 1.4% of an average male bald eagle's weight, and about 1.06% of an average female Bald eagle's weight. This is in accordance with the North American Banding Council's recommendation of 5% or less: indeed, it is well underneath the maximum.

The Math
Male Bald Eagle...
Take 8.5 pounds and multiply by 16 to convert to ounces.
  • 8.5lbs (average weight) x 16 = 136 ounces
Take 136 and multiply by 28.3 to convert to grams.
  • 136 x 28.3 = 3848 
Divide 55 (the weight of the transmitter) by 3848 (body weight in grams) for the decimal ratio of transmitter weight to body weight. Multiply by 100.
  • 55/3848 = .01429
  • .01429 X 100 = 1.429
The transmitter is about 1.429 of an average male bald eagle's weight. Use 11.5 pounds for a  for a female.

How long is the antennae?
The antenna is 7.75 inches. It protrudes from the rear of the backpack at a roughly 45 degree angle. It is thin, flexible, and made of metal. There was some worry last year that that the antenna might function like a lightning or grounding rod, putting the eagle at a higher risk for electrocution. This is not the case because...
  • The transmitter does not provide a path to ground for lightning.
  • The transmitter does not change the eagle's electrical potential.
Lightning or grounding rods are taller than the things they are sitting on and provide a very firm connection to ground. Like water, electricity has to have somewhere to come from and somewhere to flow to. The trees that eagles roost, perch, and nest in are already very firmly connected to ground through their root systems: adding a 7.75 inch long antenna does not change the eagle or the tree's connection to ground, or the path by which electricity might travel to get there. When an eagle is flying, it isn't grounded, so the antenna (which isn't connected to ground in and of itself) provides no path to ground at all.

How long will the transmitter last?
We don't know for sure. Our transmitter are solar powered. Northstar's website lists the operational life as indefinite, but probably 2-4 years: our eagle biologist had one last as long as seven years.

What's the transmitter back pack like?
It is somewhat like a child's backpack. The teflon straps or ribbons go in front of and behind both wings, and are stitched together in the front. The straps are fitted snugly underneath the eagle's contour feathers, which prevents chafing and feather damage. We don't try to trap the eagles until they have been on wing for a few weeks, which assures that they have gained flying prowess and their flight muscles are fully developed. The final stitching of the harness allows us to custom-fit it to the individual eagle's body.

This is not our set-up, but it will give you an idea of what the harness looks like: http://www.learner.org/jnorth/images/graphics/d-e/eagleW_xmitter.jpg

Do a Google image search for 'eagle transmitter harness' or 'eagle transmitter backpack' for more images.

When will it fall off?
The transmitter will not fall off. We did a great deal of research into transmitters and backpacks and worked closely with our eagle biologist to determine the best and safest type. He has had very good results with the system we are using now: eagles have carried them for a long time, traveled long distances, and reproduced with them. We decided we preferred a system that he knew worked and had data on over one we had no experience with.  
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The North American Banding Council has established a code of ethics for bird banders, and we comply by it: http://avescr.org/Descargas/NABC/English/Raptor_Manual.PDF. Our Board and Director are all passionate about birds of prey: Bob Anderson has been involved in falconry since the late 1960s and bird conservation since the early 1970s. We believe that our study of bald eagles is not harming the study subjects in the short run, and will significantly benefit Bald eagles and other animals in the long run.

41 comments:

Kathie said...

Wow! what a great piece. Thank you so much for all this information. I really appreciate all the effort you all put in to keep us informed! Thank you. Katie

Dot said...

Great article. With all the great information you gathered from D1's transmitter, there should definitely be a D2 this year. I am happy to know you are planning another transmitter for one of this year's eaglets.

Pat said...

This was tremendously informative and enjoyable to read. Thanks for your great work...Pat

Beth said...

I too am happy another transmitter will be placed. Thank you for the great information and the webcam. I love it and these eagles!
Beth

Beth said...

I too am happy another transmitter will be placed. Thank you for the great information and the webcam. I love it and these eagles!
Beth

Rich said...

I just read an article about mortality rate of spotted owls with transmitters; studied back in 1989. 48 owls that had transmitters placed on them, 37 died in the first year. 77% death rate raises serious questions.
What is the mortality rate of eagles with transmitters? If they survive, how long do they live with this attached?
Many books have been written about navigation of eagles. What new info. is being developed from this?

jeff_a. said...

Science is a wonderful thing, but at what expense? When we mess too much with nature, will nature trust us again? A code of ethics is all fine, but interfering with natural processes goes too far.

Bonnie said...

Bonnie said - What a great article. Very informative. We see them at our house during the winter months.

Bonnie said...

Great information on their travels. We see them a lot during the winter months near the Wis. River.

Ellen K. said...

If we want to learn about whether they travel with siblings or even recognize siblings once they leave the nest, why are you not putting transmitters on two or all three of them? Is there a lot of new information to be learned by putting a transmitter on only one?

Jean Camuso Hubble said...

I agree with Rich and Jeff...

Jody M. Tanner said...

Thanks for all you do in the name of research for the eagle population. And thank you for the decision to monitor only one of the eaglets.

LINDA MLADY said...

What I think of your (decision), if I owned the land of my beloved eagles nest I would chop down the tree, putting a stop to hurting my baby eagles.

Kim said...

While I do not agree with the transmitter, for the same concerns listed above, Linda, it is against the law to cut down any tree with a Bald Eagle's nest in it.

I've learned much through the Decorah webcam and am grateful for that technology. So if that tree were destroyed, how many others will miss out on the baby eagles?

LillyAnn said...

So the eagle will have the transmitter on its back forever even if it is not transmitting data. Did you ask the eagle if it is what it wanted? I would say "no"

Cathy said...

I admit I was upset when you announced putting the transmitter on D1(va) last year, but after researching the reasons why transmitters are attached to eagles, and other raptors, I found a lot of good information, especially at the CCB site. I understand not only what you are saying about habitat affinity, but also eagles from different areas migrate along the same path as others from the same area. This provides invaluable information in preserving those paths and keeping the eagles out of harms way. Also, with the transmitter and the banding, should the juvie get hurt along the way, whoever finds her will know where she came from and that also provides invaluable information to the rehab centers.

Do you think you could band all the eaglets? I would love to see the parents banded, too, should anything happen to them.

I think those who are reluctant to accept this should do a little leg work and research the reasons for a transmitter and the enormous amount of information gathered from their flights and migrations.

Thank you for doing what you know is best and taking the best care of the Decorahs.

Susan J said...

The cam is spectacular. And harmless. But use of a transmitter is overkill. Can we not enjoy the beauty of these magnificent birds and observe them without encumbering them and even endangering them with mankind's insatiable obsession with technology? Experiments involving animals are high risk. And wrong. If you are determined to continue the use of transmitters and feel that knowledge gained from them is, indeed, critical for the actual survival of the species (and I don't believe it is), and is not just a means of satisfying idle curiosity in the name of science, then at least use a design that will allow the transmitter and harness to fall off when the device is no longer operating, so that the bird will not have to wear it for the rest of its life. Please do this for the eagles and stop using them in experiments. Each life is so fragile and precious. Let the eagles be free.

Leona Mazinga said...

Human (and scientific) arrogance continues to astound me.

Susan J.s comments say it well, so I would add only this:

Just Because We Can Doesn't Mean We Should

Nancy Workman said...

Thank you for this carefully thought-out information. Same question as asked by a few others: would it make sense to put a transmitter on at least one other sibling? Seems like it could be useful to learn more about family patterns at this stage?

Survivor said...
This comment has been removed by the author.
Amy Ries said...

If you are interested in our financials and non-profit status, please look us up on Guidestar:
http://www.guidestar.org/organizations/41-1693761/raptor-resource-project.aspx

Amy Ries said...

For transmitter-based leg work and research on migration, check out this Audubon article: http://www.audubonmagazine.org/articles/birds/unlocking-migrations-secrets

donna dechaves said...

One thing I don't quite understand is that it was stated that the transmitter wouldn't be put on the eagle until the eaglets were on the wing several weeks, which makes a lot of sense. Why was it decided to do it so quickly?

lnepstad said...

I followed the link for financial information, but there are no financial reports, only one piece of info that is 10 years old. Have to subscribe to see more, supposedly. If you are really interested, you can get the financials from the State of Iowa.

lesterfamily91 said...

We have enjoyed the webcam and appreciate all of your hardwork to help make that happen. However, Please take off the transmitter and let D14 live a natural life

lesterfamily91 said...

We have enjoyed the webcam and appreciate all of your hardwork to help make that happen. However, Please take off the transmitter and let D14 live a natural life

realwealth1 said...

Is there a chance that the antenna might get caught on something like a tree branch?

realwealth1 said...

Is there a chance that the antenna could get caught or snagged on something like a tree branch?

cottage606 said...

Dear RRP... Oh, the hazzards of sharing science with the general public! It seems some either didn't read the blog or have limited reading comprehension...possibly even a lack of cranium content? I'm not a scientist, yet was able to instantly see the long-term value of the information you're already gaining, that it could even benefit species beyond eagles and that it has already highlighted the importance of the smaller waterways. Cool beans!! I also recall mention of the Center for Conservation Biology in Virginia--they're phenomenal! My personal favorite comment above was "chopping down the tree" to protect the baby eagles...LOL. Wow. Please just keep sharing the knowledge gained from your research and keep hanging tough. Hopefully you'll resist the urge to turn off the cam while you're busy creating Frankeneagles! ;D (That was supposed be funny, but if the public becomes a danger to you or the eagles, you may have to do it! C'mon people, get a grip! There are truly bad things going on in DC for you to be freaking out about!!!) Thank you Amy, Bob and others at RRP for your love of raptors and for all your hard work. (To Sharon...if Bob said that about the cam, it appears his instincts were right on. I would guess that Bob has WAY more "fame" than he ever wanted. Um, greed? Suspicion? Have you perhaps read one too many mystery novels this year?) For a larger perspective on transmitters, consider that eagles with transmitters are thriving (as already stated by RRP and other researchers) and if they were not, transmitter use would be reduced, if not discontinued--duh. Read about Hope the Wimbrel and what she has accomplished with her transmitter on!! I haven't yet read about the owls with transmitters, but there could be problems because I believe owls have to fly silently to kill their prey(?). While I'm on a roll, how many of you squawkers have exotic bird species living in your homes? How worried are you about their original/natural habitat, I wonder? Just curious. I wish someone would invent yoga for the mind..........

M Alexander said...

Whilst I understand the valuable information the eaglet will provide this noble organisation, I can't help but feel that a transmitter as obtrusive as it looks with a 7 inch antenna is going to be permanently attached to an animal I have unexpectedly connected with. Had I the choice as guardian to D14 to make this decision for her, I think I would have requested that the transmitter be only temporary with straps which degrade after a year or thereabouts. I'm not entirely convinced that permanent is fair to her. I wish her a happy and fulfilled life as the regal animal I have watched her grow into, statistic subject or not.

Linda Jegerlehner said...

I am fascinated with these eagles and very happy Bob was able to attach the transmitter to D14 -she has been such an interesting bird to watch.
Recently I saw a program which discussed the importance of South American old rain forests for North American song birds when they migrate in the winter. I had never made such a personal connection with the problems associated with rain forest clearing as I did when I realized our birds needed those trees.
Why am I talking about this now? I know people feel bad about D14 wearing the transmitter, but I think the possibilities of what we might learn could be so beneficial to D14 and all the eagles to come after her that we should support this research. What we learn from her could help improve life for eagles, all other birds, and humans as well.
D1 has given us a lot of information, and it will be nice to compare D14's travels. I wish Bob could attach a transmitter to a male eagle to see how its life might be the same or different from a female's in regard to distance covered, socialization, etc.
Thanks RRP for all you've done for the eagles and for us humans who have been fortunate enough to share your bird's eye view of their lives.
I hope I'll see the young eagles in the next few days when I travel to Decorah to the fish hatchery. It will be the second trip I will have made there this summer just to see these birds.

Deborah said...

Great video. Fun to see Bob in action loving on these birds. Thank you Bob for all that you do!

Rich said...

Cottage606: Your comment that eagles are thriving with transmitters attached, could you give me data/articles that support this? My anxiety that transmitters are totally wrong would be greatly alleviated.
Also, reasonable people can disagree. Intellectual discourse is the main reason we live in the greatest country in the world. Your comment about "cranium content" is way beneath you.

Dawn Lowery said...

Well said Rich. I would like to see those articles as well. And to Cottage606 - "cool beans"??? Really???? How could I possibly take you seriously..

AmyRies said...

A few articles on research with transmitters. My favorite is the Spanish Golden eagle:

Spanish Golden Eagle: http://www.uv.es/lolopas/ao_2007.pdf

Satellite Tracking migratory birds:
http://www.werc.usgs.gov/ResearchTopicPage.aspx?id=12

Guidelines to the use of wild birds in research: http://www.nmnh.si.edu/BIRDNET/documents/guidlines/Guidelines_August2010.pdf

Audubon article
http://www.audubonmagazine.org/articles/birds/unlocking-migrations-secrets

North American Bird Banding Council (banding, but it is a related topic.):
http://avescr.org/Descargas/NABC/English/Raptor_Manual.PDF

AmyRies said...

The transmitter is attached by sewing the straps together in front. This allows it to be custom fit. We didn't actually fit it ourselves - that was done by an eagle biologist who has fitted dozens of eagles with transmitters. Our two birds are part of a larger study of bald eagles. A paper on the study should be published within the next year or so in a raptor journal. When I have the details, I'll post.

We use a very strong thread because we don't want the transmitter to become partially detached, leaving dangling straps. That would be much more dangerous to the eagle. Our transmitters have a good history in the field - birds have survived and bred wearing them. We keep up with current technology, and if there is a better, lighter option (I've had microchips suggested) we'll use it.

The antenna won't get caught - it is a flexible wire, but too stiff to wrap around stuff.

Sharon CA said...

Does not squlech my concerns at all, Amy. It is cumbersome, just look at it. And why was it a 'temporary' transmitter last year, and a permanent one this year? The story changed. So you learn about travel patterns? And the benefit is . . . In reality, it hinders the bird over time. If you can only imagine what your life would be with a permanent contraption such as the transmitter attached to your back. Clear and simple. It has to have a negative effect on the eagle's quality of life.

Rich said...

Sharon CA: Your empathy is ethereal. Your courage to speak out is admirable. I am blessed to be in a world with people who are so caring.
Thank you, and you make my spirit stronger.

Sharon CA said...

Wow, Rich, thank-you and I appreciate it. I will keep speaking out about this issue as long as it is one.

CarKid said...

So far, I have seen little evidence that eagles are harmed by the transmitters. Comparatively, in terms of approximate weight, it would be like a person permanently carrying around 2 or 3 nickels. The size of the transmitter worries me a bit more than the weight -- air resistance on a long flight, etc. It does look as if it might interfere with mating, but experience has shown that is not the case. I can understand the underlying feeling of interference with nature; I feel it myself. But the research might well establish another good reason to preserve small rivers and other habitats, which might do more for the preservation of such places than the health of human beings. After all, the eagle is the bird of the United States of America. We should take action to preserve them.

Sharon McFalls said...

CarKid said, "Comparatively, in terms of approximate weight, it (the transmitter) would be like a person permanently carrying around 2 or 3 nickels." Where did you get that? The weight for the eagle is more like 2 - 3 pounds. Have you any idea what unnatural weight on your back, 24/7, lifetime sentence, can do? Put a 2 -3 pound back pack on, keep it on for a few days and get back to us. It will take it's toll on the bird. I wear a 3 pound vest at work, 40 hours a week, and I can tell you all about the toll it has taken on my neck and spine. I can only imagine what wearing it 24/7 would do. Not to mention the bulkiness of the transmitter and the potential hazards there. It is too cumbersome and violates the eagle's freedom. Clearly.