Thursday, December 29, 2016

A trip down memory lane: Favorites from 2016, Decorah edition!

It is time for a look back at 2016! We asked the mods for their five (or more) favorite moments of 2016 from Decorah and Decorah North. We will feature favorites from Decorah today.

Several mods mentioned ‘firsts’: first pip, first hatch, and first feeding. A few favorite firsts from 2016.

  • First feeding for D24: Mom Feeds D24 Sweetest Thing:
    It is reassuring and sweet to see an eaglet’s first feeding.
  • First pip for D25: D24 & D25 pip with beak moving - super close macro zoom: A feeding for D24, one of our first glimpses of D25, cute vocalizations (I can’t help but think of baby talk), and birdsong everywhere.
  • First glimpse of D25’s face: Does this video also show D24’s first PS? Wonderful if brief views of D25’s tiny talons and face, down still wet from hatching, and D24 gobbling down sucker roe!

Poopshoots remain a perennial favorite among mods and watchers alike. Two poopshoot moments really stood out for a few moderators…

There were a lot of miscellaneous favorites – cute, interesting, or fun glimpses of daily life at N2B!

We all missed D24 and D25 after they left N2B. But the cameras at N1 and Robin Brumm’s videos gave us a glimpse of their post-fledgling lives.

All of the mods mentioned followers, classrooms, and/or people at After the Fledge. They loved the chance to interact with classrooms, our guest moderators from teamcarnes’ class, the daily chats with followers, meeting and hanging out with eagle friends and family at ATF, and getting a chance to see Ambassador in Training Decorah (widely believed to be D20 from 2014):

Judging from readership of blogs, your primary Decorah-related concerns in 2016 were:

Have a very happy new year and thanks for watching with us in 2016!

Thursday, December 22, 2016

Nesting Chronologies

We were asked about the nesting chronologies of bald eagles. While nest timing can very from region to region (Florida, for example, is quite different from Iowa), mark your calendars as follows!
  • In the nests we watch in Iowa and Colorado, bonding and copulating behaviors become more pronounced and frequent after the winter solstice. Female eagles begin laying eggs 5-10 days after productive copulation begins. This usually happens in mid-February at the Decorah and Fort St. Vrain nests. The Norths have a slightly later chronology and probably won't lay eggs until mid-March.
  • Each egg is laid about 3-5 days apart, and incubation starts with the laying of the first egg.
  • Eagle eggs begin hatching roughly 35 to 37 days after they are laid. This usually begins in late March in Decorah and Fort St. Vrain, and mid-April at the North nest. Hatch can take more than 24 hours for any given egg.
  • Eaglets spend 75-80 days in the nest before fledging. This usually happens in mid to late June at the Decorah and Fort St. Vrain nests, and early to mid-July at Decorah North.
More on the subject! 
Eagles have been observed mating ten months out of the year, but they only produce eggs and sperm for a very brief period of time after the winter solstice (see this blog for more on that topic, or this blog for a graph of daylight length rate changes). Between solstice and egg-laying, watch for female eagles to foot and nibble males, vocalize at them, rub against them, and even mount them to indicate receptivity. Males will increase the amount of material they bring into the nest, work on the area that will underlie the nest cup, and vocalize at and with females as both sexes become more vocal. Listen for the unique and wonderful sound of the eagles vocalizing together!

A quick primer on egg fertilization in birds. Sperm needs to encounter an ovum at the infundibulum, or site of fertilization.  If sperm are too early, they will die prior to the arrival of an ovum. If sperm are too late, they can't penetrate the eggshell layers that form around the ovum in the female's oviduct. So how do birds assure fertilized eggs? They:
  • Copulate regularly. Regular copulation helps assure a good supply of sperm - especially important in an animal that regularly clears its cloaca when eliminating waste!
  • Store sperm. Sperm storage tubules maintain sperm viability, prevent stored sperm from being ejected, and continuously release sperm to the infundibulum.
  • Concentrate sperm at the infundibulum. Released sperm are passively carried to the infundibulum. Their continuous release and relatively slow drift help ensure that sperm are present when an ovum arrives.
Incubation starts immediately after egg laying begins in mid-February to early March. Eggs shouldn’t get too cold, but they also can’t get too hot, or the embryos will die. Adults sit on the eggs when they need heat and get off them when they need to be cooled. Both parents have a brood patch, a natural thinning of the abdomen feathers caused by hormonal changes, where their skin is in direct contact with the eggs to transfer warmth. Since incubation starts from the time the first egg is laid, eggs will hatch about 3 days apart in the order they were laid. Both the male and female take turns incubating, but the female, being larger, takes the longer incubation periods overnight. It is believed that her larger body weight makes her a little more tolerant to cold - important during a long inactive spell!

Once eggs start hatching in late March to mid-April, it can take longer than 24 hours for any given eaglet to complete hatch, although it doesn't tend to take that long in the nests we watch. We will announce hip or Hatch In Progress watch on Facebook, Twitter (@RaptorResource), and our website (

Saturday, December 17, 2016

Helping birds in winter!

After one of the nicest falls I can remember, winter has finally arrived. While the eagles are more than capable of handling snow and cold, I like to help (and watch!) smaller birds like chickadees, nuthatches, finches, redpolls, pine siskins, and other visitors to my yard. Here are a few tips to make winter a little easier for the birds and more enjoyable for you!

Like IHOP for birds. Looks like I need to fill the feeders again! 
  • Feed the birds! Winter is a great time to feed high-fat, high energy foods like suet and sunflower seeds. I have five feeders right now - two finch feeders (which include sunflower chips, thistle, and millet), a platform feeder with black oil sunflower seeds, a square box feeder with 'cardinal food' (black oil sunflower seeds, sunflower kernels, safflower seed, and peanuts, which also bring in blue jays and red-bellied woodpeckers), and a suet feeder. With different styles of feeder and different food choices, everyone can find something they like!  Remember, it is important to feed regularly once you have started. According to the Cornell Lab of Ornithology, little birds like chickadees can lose 25% of their body weight on a cold night. If birds come to rely on you for a constant supply of food that isn't available when storms hit or the cold really starts to bite, they might not survive.

    I had roughly 61 birds at my feeders this very cold morning, including a male cardinal, juncos, gold finches, chickadees, a sparrow, hairy woodpeckers, downy woodpeckers, red-bellied woodpeckers, and a white-breasted nuthatch. A quick tip: more perches can mean more birds. If you can't set up feeders near trees, you can install additional perches near your feeders. And you can also...
  • Plant and landscape for birds! We are fortunate to have a lot of trees in our yard. The feeders are set up near two cedars, which provide nice, thick cover; two elms, which provide a lot of branches for perching; and an oak woodlot. We left part of the woodlot unmowed this fall, which means plenty of vegetation for perching and additional seeds for small foragers. If you can, plant native shrubs and bushes and leave some tall vegetation standing to provide cover, food, and perches for wintering birds.
  • Install roost boxes. Another suggestion from Cornell. Roost boxes will help protect any birds that nest in boxes or cavities, including bluebirds, chickadees, titmice, nuthatches and small woodpeckers. A good roost box keeps the birds' body heat contained, has interior perches, and can be placed on a metal pole or wooden post. They are available in stores, or you can make your own. Follow this link for roost box-building instructions. Note: I haven't tried this since we have trees, brush piles, and outbuildings. But I plan to build one over Christmas break - it looks like a great idea and I would love to monitor one during cold weather!
  • Water birds. Let's get something straight: It is not true that heated bird baths kill birds. I don't know how many times I have been told not to water birds because they will get water on their feet or feathers and freeze to perches or become encased in ice. Not true! Flowing water is a valuable commodity in winter and heated bird baths will help birds while attracting more of them to your yard. Make sure to keep them cleaned and filled if you commit to watering.
Here's to a very happy and well-fed holiday to all of the birds! Looking for a holiday craft activity for children? My kids and I used to make these easy and inexpensive bird treats: A little warning - this craft is fun, but be prepared for clean-up!

Did you know? Another bonus to feeding birds - you can join Cornell's Backyard Bird Count! Learn more about it here: I plan on counting birds and watching for eggs in Decorah!

Tuesday, December 06, 2016

Report on the Unhatched Eagle Egg from N2B

Unhatched egg, N2B
We received the results on the unhatched egg from N2B. As watchers might recall, one of the eggs failed to hatch. We thought the embryo might have died early in formation, but according to tests run by Iowa State University, the egg was never fertile. How could that be?

A quick primer on egg fertilization in birds. Sperm needs to encounter an ovum at the infundibulum, or site of fertilization.  If sperm are too early, they will die prior to the arrival of an ovum. If sperm are too late, they can't penetrate the eggshell layers that form around the ovum in the female's oviduct. So how do birds assure fertilized eggs? They:
  • Copulate regularly. Regular copulation helps assure a good supply of sperm - especially important in an animal that regularly clears its cloaca when eliminating waste!
  • Store sperm. Sperm storage tubules maintain sperm viability, prevent stored sperm from being ejected, and continuously release sperm to the infundibulum.
  • Concentrate sperm at the infundibulum. Released sperm are passively carried to the infundibulum. Their continuous release and relatively slow drift help ensure that sperm are present when an ovum arrives. 
After removal from N2B
It is good to know that egg number one didn't contain an embryo, but why wasn't it fertilized? Three suggestions based on a simple idea: sperm wasn't present at the infundibulum when the first ovum arrived. 
  • While eagles have been observed copulating ten months out of the year, males don't produce sperm year round and they don't store it very long once production is underway. Perhaps Dad wasn't producing sperm in time for Mom's first egg. Sperm production is not required for pair bonding.
  • Mom may not have had enough sperm stored to concentrate sperm at the infundibulum in time for ovum #1.  
  • Age might be impacting reproductive success in either Mom or Dad. While free-living animals don't tend to have 'menopause' - a long stretch of time in which they do not bear young - age does impact fertility.
Some watchers have expressed concern that age might be a factor in the failure of egg number one. It isn't especially likely in Mom based on what we know. In general, a female bird that produces a healthy, intact egg is most likely fertile. Reduced fertility in our 'elderly' female peregrine falcons tends to be accompanied by changes in the amount of eggs laid, egg color, shape, and condition. Eggs might be unusually colored, pitted, or shaped - all things we saw at Xcel Energy's Sherco facility in 2014 and 2015. While we don't have a lot of data about senescence and egg production in bald eagles, wild eagles are generally assumed to live for 20-30 years. Given that Mom is just fourteen years old, age-related fertility impairment seems unlikely. 

So how about Dad? We believe he is at least 19 years old, although we don't know exactly how old he is. Senescence and sperm production in birds is a little complicated. Research indicates that aging impacts sperm quantity, quality, and motility in birds, and eggs fertilized by older males hatch at reduced rates when compared to those fertilized by younger males. But even with reduced motility, the sperm of older males tends to perform better than the sperm of younger males in a female bird's body. In short, older birds have less sperm than younger birds, and the sperm they have is less motile and of lower quality. But studies have found that older birds are more likely to fertilize eggs than their younger counterparts, even if those eggs are less likely to hatch.

Why are older male birds more successful at fertilizing eggs? The study Senescent sperm performance in old male birds found that obstacles to sperm movement in a female bird's reproductive tract affected older males less than younger males. I would love to see research on the role that skill and pair bonds play in sperm retention (I am defining 'skill' as actions taken by the male to assure a high degree of receptivity in his partner). We know that at least some female birds are able to preferentially reject the sperm of less desirable males, that female birds who mate with familiar males often produce more fertilized eggs with more egg mass than those who mate with novel males, and that the success of novel mating is highly dependent on male behavior. Reproduction is clearly much more complicated than we used to think, and it is obviously past time to drop the pejorative term bird-brained!

Having said that, we are back to the question of Dad's fertility. One infertile egg doesn't really give us enough data to come to any conclusions, but it is very helpful to know why the egg didn't hatch. We will be documenting whether or not nest production continues to decline at N2B. Thanks to John Howe, Kike Arnal, Pat Schlarbaum, Dr. Ensley, and Iowa State University for giving us more insight into the lives of the birds we follow. We are hoping for the best for our beloved Mom and Dad!

Did you know?
  • Sperm competition can result in speedier sperm among animals that have multiple mates while ovulating. Female mice, for example, take multiple mates and can't reject or store sperm long, so speed is important!
  • Why didn't the egg explode? A decomposing embryo rapidly produces gasses that can explode an egg, but this egg didn't contain anything except (presumably) Mom's blastodisc. It was also kept relatively cool and protected from direct sunlight by grass and nest detritus. John really had to dig for it! He told us that he dug through roughly a 5-gallon peregrine gravel pail worth of stuff to find the egg, including a squirrel's skull!
  • Would a receptive female in a long-term pair be likely to produce more eggs? I had very little time to follow up on the question, but here is one study that touches on it:
Things that helped me learn about this topic
So does this mean it is clearly the magic in Dad's many, many sticks? ;) All jokes aside, Dad spends a great deal of time working on the nest and providing food, although Mom is more than capable of building and hunting on her own. We tend to define the reproductive season as starting at the beginning of active copulation or egg-laying. But today's daily activities help cement the bond between Mom and Dad and may result in increased productivity months from now: more fertilized eggs with higher egg mass, more hatched eggs, and heavier weights in nestling eaglets during critical stages of growth. We are learning that eagle reproductive success depends on far more than the brief period of time they spend engaging in productive copulation.

Monday, November 28, 2016

2016 by the Numbers!

To help kick-off Giving Tuesday on Tuesday, November 29, we wanted to talk about what got done in 2016. Here are the things your donations helped us get done! Please donate to the Raptor Resource Project to help us continue our work in 2017 and beyond! 

Online Interaction and Education
Since January 1, 2016, we have:
  • Provided 1,785 hours of chat on the Decorah eagles channel, including 449 hours of dedicated educational chat. Our Decorah North group provided 576 hours of moderated chat, including special coverage following the deaths of DN3 and DN2. 
  • Posted 364 times on Facebook. Topics and photos included the Decorah Eagles, the Decorah North Eagles, the GSB Peregrine falcons, the Fort St. Vrain eagles, tracking D24 and D25, Robin Brumm's trips to Decorah, peregrine falcon banding, nest box work, and many other topics related to our nests and birds. Posts were shared from Neil Rettig Productions, SOAR, the Cornell Laboratory of Ornithology, and Jim Brandenberg's 365 Nature project. 
  • Wrote 31 blogs. We addressed questions about the eagles, the nests (Is N2B big enough?), nest intruders, eaglet growth and development, the proposed 30-year take of eagles, and the deaths of DN2 and DN3, and much more!
  • Expanded our online offerings to This ads-free site is presently one of two that streams the Decorah Eagles North channel.
I need to give a shoutout to our amazing volunteer moderators. I have said it before and I will say it again - our volunteers make our pages the best on the web and we could not provide our online educational program without their help!

Monitoring, Banding, Trapping, Recovery, and Nestbox Maintenance
Since January 1, 2016, we have:
  • Monitored over 50 peregrine falcon and bald eagle nest sites and potential territories in Minnesota, Wisconsin, Iowa, Illinois, and Colorado.
  • Banded 76 falcons at 25 sites in Minnesota, Wisconsin, Iowa, and Illinois between May 20 and June 16 - a record for us! Our northernmost territory was in Cohasset, Minnesota and our southernmost territory was in Peoria, Illinois. As always, we reported all banding and follow up data to the Bird Banding Lab and the Midwest Peregrine Society.
  • Installed 2 tracking platforms on D24 and D25 in July. Thanks to the platforms, we know that D25 was killed in a collision with a car in September, but D24 is still going strong! 
  • Retrieved DN2's body from Decorah North in May, and the unhatched eagle egg from N2B in September. DN2's autopsy can be found here. We are waiting for a report on the egg. 
  • Changed gravel at 3 peregrine nest boxes in October and November. The US Bank box in La Crosse also got a new top and we fixed the private camera at the Greysolon box in Duluth.
Thanks to our utility, industrial, and landowner partners for all of their help and support! A huge thanks to Brett Mandernack for including 'our' eagles in his studies and for sharing all of the data about their whereabouts and fates. Thanks also to David and Ann Lynch for their help with the transmitter project. We couldn't do it without all of you!

Camera Research and Installation
We focus on camera installation and nest box maintenance in September and October. Bald eagle cam work ends on October 1st, which is considered the start of the active season in our area. Peregrine falcon work can be done later since we don't tend to see much of them again until late February or early March. Even territorial falcons are less defensive of their nest sites this time of the year.
  • John Howe, Kike Arnal, David Kester, David Lynch, Ann Lynch, John Dingley, Amy Ries, Bill Heston (Xcel Energy), and Pat Donahue (also from Xcel Energy) installed a total of six cameras and four microphones at N1, N2B, Decorah North, Fort St. Vrain, and GSB between September 17 and October 16. We also provided technical support for the Seneca Nation of Indians (a bald eagle cam) and the Marshy Point Nature Center (Marshy Point ospreys). The installations took roughly 900 hours total. 
  • John Howe put in hundreds of hours researching, ordering, and testing cameras this year. While the majority of our installs are done in September and October, camera and streaming research take place year-round. In 2016, we began to move towards 4K at Decorah North and GSB - a big jump for us - and improved the audio at Decorah and Decorah North.
Other Stuff
  • We threw our annual After The Fledge party between July 14th and July 16th. Almost 100 eagle fans and volunteers had a blast celebrating the Decorah eagles and Decorah itself!
  • We provided ongoing technical support to followers who experienced problems watching our eagles, viewing Facebook, and participating in chat. Over 800 followers received support via our website, and an unknown number received support via our Facebook and Twitter.
  • We partnered with Ustream to provide temporary ads-free viewing to 347 teachers and their students.
  • John trained 4 volunteers to operate our cameras remotely - a new and very welcome step for us and our followers. 
Thank you for all of your support and for your donations. They make a difference and we couldn't continue to do it without them! 

Wednesday, November 23, 2016

A Reflection and a Thanksgiving

I found myself in an unusually reflective mood earlier this week. Today, November 23rd, was Bob Anderson's birthday. It seems like a good time to take stock of where the Raptor Resource Project has been, where it plans on going, and what I have to be thankful for.

Bob and Dave Hecht banding at Lansing in 2010
For those of you who don't know, Bob founded the Raptor Resource Project to propagate and release peregrine falcons. He was the first person to successfully breed peregrine falcons in Minnesota. MF-1, one of the first falcons he produced and released, became the first returned falcon to breed in the mid-continent following the species' extirpation in the mid-1960's. It took an incredible amount of work to keep the peregrine falcon from joining the long list of species that will be mourned on the remembrance day for lost species. I am thankful that the peregrine falcon is still with us. Where we have a will, we have a way.

I am thankful to have met Bob. He responded to an ad my little writing business was running back in 1994. I began by writing grants, but very quickly moved into field work. Did I want to attend a banding and take pictures? Yes! Did I want to hold falcons? Yes! Did I want to rappel? Yes yes yes! The writer William Least Heat Moon said in the Wonsevu chapter of the book PrairyErth that "I'm not sure what to make of it, but I think a dream can set you on another path." Bob's dream of restoring the peregrine falcon set many people's lives on another path.

Banding at Xcel's Allen S King plant in 2005
Believe it or not, we moved into internet cameras almost accidentally. Bob set up several local monitors so that power plant employees and visitors could watch peregrine falcons. If I remember correctly, Mike Miser from the Allen S. King plant in Oak Park Heights, Minnesota, suggested putting their camera online. 'Mae's Internest' hatched in 1998, making Xcel Energy's corporate website the busiest in the world for the first quarter of 1998. It uploaded a still image of Mae's nestbox every two minutes...a technical triumph at the time! That year, we also began a three-year study of heavy metals in utility falcons with the Electric Power Research Institute, Xcel Energy, and Dairyland Power. We worked with Dan Orr and Ken Mueller at Xcel Energy and John Thiel at Dairyland Power. All three men have since retired, but the paper can be found here: I am thankful to have worked with the fine men and women employed at America's power plants. The utility-peregrine program is an example of the ways in which humans can support wildlife even in the unlikeliest of areas. You guys are awesome...and great fun, too!

Bob was also working on his cliff release project. Back in 1994, he began to believe that nest-site imprinting was preventing the crossover of peregrines from power plants to cliffs. The Iowa DNR was very interested in working with Bob, so he picked up lock, stock, and barrel to move down to Bluffton, Iowa in 1996. He did a successful pilot release on the Upper Iowa river in 1997 and released a total of 19 falcons from Hanging Rock at Effigy Mounds National Monument in 1998 and 1999. The Upper Iowa hackbox can still be seen from the river, although the Effigy Mounds hackboxes are long gone. In 2000, our cliff-released falcons became the first falcons to return to the cliffs of the Mississippi. I remember going to see them quite well, since I was very pregnant with my last son. I did a lot of crazy things for and with Bob, but the only time I remember him being really worried about me was just after I huffed and puffed my way up the back of Queen's Bluff. Pat Schlarbaum's story about peregrine recovery includes information about our cliff releases. It can be read here: I am thankful to have played a small piece in this story, and very grateful to the men and women of the Iowa DNR who supported Bob's work.

In 2006 and 2007, Bob was working with Neil Rettig on the movie American Bald Eagle. After the two wrapped up, Bob said "Wouldn't it be fun to put this nest on the internet?" We made Bob's dream a reality in 2009, when the Decorah Eagle Cam uploaded an image to Xcel Energy's website every two minutes. In 2010, Luther College hosted a live feed. In 2011, we moved to Ustream and the Decorah eagles became a worldwide sensation. While we celebrated the eagles, Bob also mourned the loss of his dear friend and fellow falconer Rob MacIntyre, the 'mad scientist' who was featured so prominently in the movie RaptorForce. Rob did a lot of the work on our earlier cam systems, and his death was a real blow both personally and professionally. I am thankful to have known him and his wonderful wife Jan. They brightened every room they entered.

John also likes to rappel!
While Bob never lost his drive to recover birds of prey, he suddenly had a new focus. He was deeply engaged in using our bird cams to reach learners and provide a palliative window to the outside for ill, injured, and bedridden people. Online education became a major focus, but cameras still needed to be researched and purchased, and HD was increasingly looking like the next step. Enter John Howe! John began working with Bob to research cameras and camera technologies, including solar/wireless technologies (Rob installed our first solar/wireless system back in 2003) and HD. The longer Bob worked with John, the more he was impressed. Shortly before Bob's death, he let us all know that John was to follow him as Director of the Raptor Resource Project.

This brings us up to the present. In the year since Bob's death, John has worked diligently to keep up with camera and streaming technology, deploy cameras, expand our online educational offerings, honor Bob's legacy, and secure funding (an organization doesn't run very long without money). He has more than proven himself as a director and a leader. I am thankful for John Howe and only wish that Bob was here to see the positive change that John has brought to the Raptor Resource Project.

So where do we go from here? We are sustained by our mission: to preserve and strengthen raptor populations, expand participation in raptor preservation, and help foster the next generation of preservationists. We follow our vision: to deepen the connection between people and the natural world, bringing benefits to both.
  • Education: We are looking at ways to improve and increase our educational offerings. In addition to the online interaction we already offer through our unparalleled team of moderators, we are looking at curriculum, educational videos, Skype, short movies, and other ways to reach out to learners of all age and circumstances.
  • Preserving and Strengthening Raptor Populations: We will continue to monitor our nests, band falcons, consult on nestboxes and habitat for a variety of species, provide input on conservation issues, and work with federal and state wildlife agencies to benefit of birds of prey. We are also looking at ways to strengthen existing partnerships and build new ones. How can we connect our passionate followers with organizations looking for volunteers? How can we work closer with our utility and industry partners on providing or improving habitat for the many birds that nest on or use utility land and water in other ways? How can we advocate for birds of prey? We have done a lot, but we can do more. We stand on the shoulders of giants!
  • Fostering the Next Generation of Preservationists: In addition to our online educational program, we are looking at an educational endowment in Bob Anderson's name. We will have more information about that early next year. An educational endowment seems like an appropriate way to honor Bob's legacy.
  • Connecting People with the Natural World: Researching and deploying cameras is a lot of work. Fortunately, we have a director who truly enjoys it! We will continue to do our best to connect watchers with the natural world using up-to-date, unobtrusive technology. A challenge for me: how do we develop quantifiable data from the thousands of hours of footage and anecdotes we've collected? Our knowledge has already changed since we first began watching the eagles (remember eagles are always monogamous?), but there is so much more to learn! 
So what else am I thankful for? 
  • I am thankful for fans of the Decorah eagles and our other birds. Please, keep emailing and mailing your stories and art. You have deepened our lives an immeasurable amount.
  • I am thankful for our amazing volunteers. In addition to your incredible work, my life is better for having known you. I've said it before and I'll say it again...your work makes us the best site on the web!
  • I am thankful to our Board for providing direction and guidance. 
  • I am thankful for an unexpected and unlooked for gift: the honor to be part of the Raptor Resource Project's work. My 1994 self - I was 28 years old! - had no way of knowing what saying 'Yes' to Bob's first request would lead to. Bob, we will remember and celebrate you until we join you.
Thank you, everyone. I'm going to close with a link to a favorite blog I did on Bob back in 2012: Watching Bald Eagles. The Raptor Resource Project wishes you and yours a very Happy Thanksgiving!

Tuesday, November 08, 2016

Where did all of those eagles come from?

Decorah North watchers know that we've seen an incredible number of eagles in around the nest, especially November 4th through November 7th. The tally looks something like this:
  • Friday evening, November 4th: What appear to be two sub-adult eagles are seen in the vicinity of the nest. A lot of vocalization can be heard off-screen, including chattering and pealing. Video:
  • Saturday, November 5th: At about 8am, an intruding adult is in the nest with a sub-adult perched nearby. Mom and Dad North chase them off. At 6:03pm, a juvenile bald eagle perches on a branch near the nest but is chased away by Mom North. Chattering and pealing is heard offscreen several times throughout the day. Video:
  • Sunday, November 6th: A juvenile eagle is spotted on a lower right branch near the nest at 9:00am, but the true follies don't get started until 1:30pm, when an intruding adult female flies into the nest with two sub-adults (or an juvenile and a sub-adult) in hot pursuit. There may have been a third sub-adult in a tree near the nest, and there was definitely another sub-adult in a tree in the pasture. The immature and adult intruders are all driven out, but another adult (or the same one - we don't know) shows up later with food and is driven away. A lot of pealing and chatter can be heard off screen throughout the day. Video:
  • Monday, November 7th: A sub-adult eagle visits the North nest to play house at about 7:30am:, followed by a pool party later in the day, when five immature eagles, one adult eagle, and two sandhill cranes were counted in a stretch of the stream that flows to the east of the North nest:
We are getting asked why there are so many intruding eagles here as compared to Decorah, and why so many eagles (and cranes!) right now. While the North Nest has tended to have more intruders, we haven't seen anything quite like this before. A few ideas:

On the question of location (North versus Decorah)
  • The North Nest is in a wilder area with more forests and natural terrain. While Decorah is very beautiful, it is a city on the eastern edge of an extensive agricultural area that stretches across the entire state. Decorah and areas west have much less habitat for wild animals. While only one of our tracked eagles have been seen at the North nest, many of them have visited the North area.
  • Consider an eagle migrating from Ontario to winter along the Mississippi. It will most likely fly along the west shore of Lake Superior before it peels off the tip where Minnesota and Wisconsin meet. At that point, it is about a 150-mile flight almost straight south to Lake Pepin - something eagles can do easily in a single day, especially if the winds are favorable. If they aren't, Wisconsin's lake country offers plenty of habitat for rest and relaxation. Once our eagle gets to Lake Pepin, it might chose to stay - many eagles do - or it might go further south to, say, Eagle Valley. The shorter straight-line path does not follow the river but cuts in-country through the vicinity of the North Nest, narrowly missing Decorah.
  • The North eagles are living just inside a north/south wind-funnel of sorts that cuts through the hills and channels wind - and birds - for miles. Topography influences migration in many birds, including bald and golden eagles. Looking at the terrain, it is no surprise at all to see eagles congregating here - even if the Norths don't exactly put out the welcome mat! 
In short, the North eagles are living in a region that has more habitat for bald eagles and other animals, is in a relatively straight line between critical upper and lower stretches of the river, and is in a long north/south valley that funnels wind and aids migration.

On the question of timing (why now)?
I asked bald eagle expert and board member Brett Mandernack if the eagles he is studying had left their summer grounds. He replied that they had, although given the warm weather, many were staging in Wisconsin and along the Mississippi river north of Eagle Valley. Presumably, these are eagles on their way south to somewhere else, but in no hurry given the weather. 

Unlike many birds, bald eagles migrate almost exclusively during the day. They rely heavily on thermal soaring to aid their flight, so a warm, sunny day with favorable winds can send eagles soaring by the thousands.

Let's look at the wind maps from the week of November 4, 2016. Wednesday through Friday would presumably have been excellent migration days: especially Thursday, which had favorable winds in addition to wonderful weather! But the winds started to change on Friday and were unfavorable from Saturday afternoon through at least late Monday afternoon. Why would eagles go anywhere if they had access to food, water, and high-quality habitat? The area around the North Nest provided a perfect staging spot for migrating eagles headed south. Perhaps large groups of eagles could have been found in many valleys in NE Iowa this weekend. We were fortunate to get to see these!

Chasing an intruding juvenile eagle from the North Nest

Chasing an intruding adult eagle from the North Nest

A visiting - and playful! - sub-adult eagle

Immature and adult eagles at the river east of the nest

Bathing - and interacting - at the river's edge

Sandhill cranes and an adult bald eagle
Chasing an intruding adult eagle from the North Nest

Did you know?
  • Juvenile eagles are fledglings in their first year. They are a darker brown than sub-adult eagles, with less mixed white and lighter brown plumage. Sub-adult eagles are 2-4 years old. They have very mixed plumage compared with juveniles and adults. Adults get their white heads and tails at around five years of age. Immature can refer to juvenile and sub-adult eagles. For more on aging eagles by plumage, visit this website:
  • Although bald eagles take advantage of solar power by migrating during the day, many birds migrate at night. It is believed that night migrations allow them to avoid heavy winds and storms, since nights are often calmer; keep away from predators, especially birds of prey that hunt and migrate during the day; and preserve water and energy, since cooler night-time temperatures will induce less heat-related panting.
  • Check out Brett Mandernack's .pdf of D1's migration paths. You can see a real preference for direct lines, especially on repeat journeys. She tended to cut down pretty directly through WI, unsurprisingly passing through the North Nest region, although she was never at the nest or its vicinity that we know. 

Thursday, November 03, 2016


Filed under #musings. A recent study on animal personalities got me thinking. Are the differences we see from nest to nest a product of our imaginations, the surrounding area, or their personalities?

Between 2003 and 2015, we watched bald eagle families on four territories: Decorah and Decorah North in Iowa, Fort St. Vrain in Colorado, and Eagle Valley in Wisconsin. They were very similar in their broadest outlines, since all four territories:
  • Were inhabited year-round by a territorial pair of eagles.
  • Were close to bodies of water.
  • Had distinctive seasons that included cold snowy winters, short unpredictable springs, and hot summers.
  • Were near what appeared to be ample food supplies: the trout hatchery in Decorah; a river, watering hole, and prairie dog colony at Fort St. Vrain, a trout stream and farms at Decorah North, and the Mississippi river at Eagle Valley.
However, watchers of the Decorah and Decorah North nests observed some big differences between the two last year.

At Decorah
We have been collecting data on this territory since 2006, when Neil and Bob began filming American Bald Eagle. We don't know Dad's age, although he is older than Mom. Based on her barely-adult plumage when she began nesting here in 2007, she turned 13 in 2016. Both eagles are experienced parents.
  • Both parents spent a lot of time on nestorations: bringing in sticks, arranging sticks, and moving sticks. 
  • The 'pan-tree' was almost always full. It wasn't uncommon for the nest to contain four or five prey items - not surprising, since Dad was observed bringing in as many as five fish in one hour! 
  • Both parents fed young on a regular basis. While Mom tended to take over feeding, Dad fed when he had a chance. The eaglets were fed together and separately. Human watchers believed that Mom and Dad tried to make sure both eaglets got sufficient food. 
  • A parent - usually Mom but sometimes Dad - was always present in the nest until long after the eaglets could thermoregulate.
  • The eaglets showed less aggression towards one another.
  • Fish made up a larger part of the eagles' diet.
  • Egg-laying started on February 18.
At Decorah North
We have been collecting data on these two eagles since February of 2016. We do not know how old either eagle is (although both appear to be full adults), how long they have been together prior to last fall, or how long they have been parenting.
  • Less time was spent on all aspects of nestoration during the period we were able to watch both nests. Fewer sticks were brought in and the eagles spent less time moving and rearranging them.
  • The parents did not cache nearly as much food in the nest. 'Field-dressed' prey was more commonly brought in than entire chunks or whole bodies that needed defurring or descaling.
  • Young were not fed nearly as often and separate feedings were not as common. Human watchers believed that Mom and Dad did not try to allocate food evenly between the eaglets.
  • Parents were not always present in the nest. Human watchers believed that they were more attuned to the brooding needs of the two older eaglets versus the youngest one.
  • The eaglets showed a great deal of aggression towards one another. Sibling aggression was a factor in DN3's death.
  • The prey base was wider and did not include as much fish as the Decorah nest - although based on a journal by Sherri Elliott, fish still comprised around 66% of their diet. It included opossum, muskrat, raccoon, fawn sections, rabbit, mink, cow placenta, birds, waterfowl, a cat, and unknown pieces of meat.
  • Egg-laying started on March 11.
  • The North Nest had more nest intruders and slightly harsher weather.
At the time, we believed that the difference in parenting styles was driven primarily by food availability at each nest. Since the Norths brought less food into the nest, it made sense that less food might be available overall, and their relative absence could be explained by the need to spend more time hunting. Food was also clearly a big factor in eaglet aggression, which tended to determine who was fed first or at all.  Our conclusions were consistent with earlier studies of bald eagles conducted at Besnard Lake, in Alaska, and on Chesapeake Bay. You don't have to watch eagles very long to realize how important food is. But could eagle coping styles/personalities also be playing a role? 

Let's start with defining the term 'copying style'. Jaap Koolhaus (Koolhaas et al. 1999, 2010) describes a coping style as a correlated set of individual behavioral and physiological characteristics consistent over time and across situations. Researchers divide coping styles into proactive and reactive groups:
  • Proactive individuals respond to stressful situations with action. They build rigid routines, explore territories quickly, develop superficial maps, tend to be offensive towards conspecific rivals, are impulsive in decision-making, score high in frustration tests, take risks in the face of potential dangers, and are novelty seekers. Perhaps as a result of their routines, they are less responsive to short-term changes in their environment. 
  • Reactive individuals respond to stressful situations with immobility. They are less likely to build rigid routines, explore territories slowly, develop deeper maps, and tend to be less offensive towards conspecific rivals. Perhaps as a result of their flexibility, they are more responsive to short-term changes in their environment. 
So how might behavioral type affect local space use in bald eagles? Unsurprisingly, it is a complex question. As defined above, the North adults seem proactive (quick, active, aggressive, less responsive to environmental changes and external stimuli) and the Decorah adults seem reactive (slower, less active, possessing a deep understanding of the territory, very responsive to environmental changes and external stimuli). One of the things that watchers commented on was the absence of Mom and Dad North when compared to Mom and Dad Decorah. Several studies have found that proactive individuals show a wider ranging space use than their reactive counterparts. The North eagles spent less time in the nest and on the nesting tree last year. Was that driven only by food availability or did a deep-seated need to range also play a part? We also discussed the differences in parenting styles quite a bit. The Decorah eagles seemed to human watchers to be much more reactive to the needs and behaviors of their eaglets than did the Norths. Did personality have anything to do with it? 

A lot of the narrative around both eagle families seems to fit nicely into a proactive/reactive box. But what about prey piling and nestoration? Watchers identified prey piling as a big difference between the two families. The Decorah eagles piled prey high (and have ever since we began watching them), while the North eagles seldom cached prey in the nest (although left-over turkey feathers piled up, they didn't make a meal). Similarly, the Decorah eagles spent a lot of time working on their nest (Dad's sticky OCD, anyone?) when compared to the North eagles. These seem like rigid behaviors, not flexible responses to the environment, which puts them firmly in the proactive category. It could be argued that, unlike the Decorah eagles, the Norths didn't flexibly respond to changes in their environment (eaglets) with changes in their behavior (caching prey). However we categorize their behavior, both pairs of eagles appear to be using environmental information in different ways.

It hasn't been that long since it was taboo to think of animals as anything other than clinical study subjects. Changes in our way of thinking and advancements in research and study techniques have altered that. I am firmly convinced that personality plays a part in the unique behaviors seen at each nest (although food remains important) and I am looking forward to more research on the topic.

Note 1: Dana Bove of the Boulder County Audubon contacted us about bald eagle monitoring. He developed an Excel worksheet to monitor nests outside of the active reproductive period, i.e., when eagles may be in and around the nest, but aren't productively copulating, laying eggs, incubating, or caring for young. We were very interested in them given the differences in the Decorah and Decorah North nests. How big were those differences in behavior? We received permission to use his protocol and put it online here. Please feel welcome to start sharing your observations via the tool. This is a bit of an experiment for us, so feel welcome to share feedback as well!

Note 2: Some watchers believe that parental experience also played a role. Like many animals, eagles get better at basic parenting skills with experience. Could some of the differences in preparation and provisioning also be a matter of an experienced parent at the North Nest?

Note 3: Could nest invaders be another piece of the puzzle? Eagles enthusiastically steal prey from one another and hungry hawks will sometimes invade as well. Could the difference in prey piling and preparation be in part a response to potential competition and nest invasion? A lot to think about!

We see proactive and reactive behaviors in nesting peregrine falcons when we handle them for banding. Some falcons foot and bite the entire time, while others are very docile and don't put up a struggle at all. A few observations...note that these are anecdotal:
  • Highly aggressive females seem to replace highly aggressive females. I can think of at least three sites where female falcons were dangerously aggressive. We've never had anything but dangerously aggressive falcons at those sites. 
  • There is a general belief that highly aggressive falcons produce highly aggressive offspring, although to my knowledge it has never been formally studied.
  • Footy, bitey males tend to be older than female siblings based on plumage growth. 
A study on crows found that dominance-related parameters of age and sex did not coincide with proactivity. I wondered about this since older, bigger eaglets tend to be more dominant, and older nestling falcons are more likely to be aggressive when handled. In effect, a study on this would be looking at whether birth order influenced personality/coping strategies. We plan to start assessing docility in nestling falcons next year for comparison with their behavior should they survive to adults. We will also keep notes on dispersal - so keep those band numbers coming!


Wednesday, September 28, 2016

Mississippi Kite Nest- An Historical Moment for Wisconsin Birding

Written by Dianne Moller, Director of Hoo’s Woods Raptor Center

Nestling MIKI
It was a hot day on August 23, 2015 when Rhoda Grossnick, a resident of Janesville, brought a young bird to the Hoo’s Woods Raptor Center (HWRC). In my 18 years as the Center’s Director, I’d never seen this type of bird before.  After posting a photo on Facebook, several biologists in southern states quickly identified the mystery bird as an immature Mississippi Kite (Ictinia mississippiensis).  The bird was just learning to fly and appeared to be about six weeks old.  It was critically low in body weight and needed food. Worse yet was that its vision was impaired, a symptom of West Nile Virus. I contacted the Wisconsin Department of Natural Resources (DNR) and, to our knowledge, this was first Mississippi Kite ever recovered in Wisconsin.

We weren’t sure where it came from but, judging by his age and condition, I was certain it had not traveled far.  In time, we named it “Wrong Way.” The bird is not releasable due to both its restricted vision and the abnormal molting of its tail feathers.  With permission from the U.S. Fish and Wildlife Service, it remains with us as an education ambassador.  

Adult MIKI in stick nest
I was not totally surprised when, in late July of 2016, I received a call from Dr. Jane Anderson. She stated that an adult pair of Mississippi Kites was seen in the same vicinity where Wrong Way had been found last year.  Dr. Anderson saw Wrong Way at one of our education programs and was able to identify other members of its species. Immediately, I drove to check out the sighting and sure enough, there were two adult kites sitting about 300 feet apart, each in a snag at the top of a dead tree.  I reported the sighting to the Wisconsin DNR state ornithologist Ryan Brady.

Several days later, DNR staff were able to locate a nest containing one feathered chick. The tiny stick nest sits high in a tree in a residential neighborhood. While investigating this siting, I spoke with a landowner who said her nine-year-old son, told her that a “Bald Eagle” was nesting in their front yard. He assumed this because the chick had a white head.  This was long before any of us realized the kites were here.   She told her son they were some type of hawk but didn’t think anything was unusual about them. It’s a sure bet that most folks in the Great Lakes region wouldn’t recognize this species.

MIKI feeding
This is the first active Mississippi Kite nest to be documented in Wisconsin. However, it seems logical that Wrong Way could have been produced at this same location, possibly from the same pair of adults, in 2015. All parties agreed not to disclose the exact location in order to avoid unwanted human disturbance to both kites and the nearby residents.  

Kites are relatively small, similar in size to a pigeon, and a member of the hawk family.  Their diet consists mainly of dragonflies, an occasional small bird, and other insects.  They are known to transfer food from their feet to their beaks in flight.  In recent years kites have been expanding their range in the U.S. nesting as far north as New Hampshire, Illinois and Canada.

This is an exciting development on two fronts. First, is that the Mississippi Kite has finally been confirmed as a breeding species in Wisconsin. And second, is that wildlife outreach programs, conducted by organizations like Hoo’s Woods Raptor Center, can be shown to have a positive impact on raising the public’s awareness and knowledge about Wisconsin’s rich wildlife resources.

The Hoo’s Woods Raptor Center is proud to have played a small part in this historical event.  Attend one of our education programs and see for yourself that education can make a difference.

Monday, August 15, 2016

Celebrating the Centennial! 100 years of Bird Conservation

On this date in 1916, the first Migratory Bird Act was signed between the United States
and Canada, serving as the catalyst for a century of bird conservation actions. At the turn of the twentieth century, bird populations were in peril as a result of unregulated shooting for the food and fashion industries. Recognizing the need for collaboration to protect species that traverse their borders, partners in the United States and Canada drafted an agreement to cooperatively manage and protect birds that migrate internationally. The act was the first international agreement forged to protect wild birds, and among the first to protect any wildlife species.

Mom and Dad Decorah don't migrate, but many of the birds we watch do! D1 went to Canada for the summer, while many of Eagle Valley's eagles visit the United States for the winter. North American peregrine falcons have been reported on oil rigs in the Gulf Coast (Candace W/Z, a bird that Bob banded), Chile (the incredible Island Girl), and Costa Rica (the lovely Inmaculada), just to name a few. As Scott Weidensaul says: "At whatever moment you read these words, day or night, there are birds aloft in the skies of the Western Hemisphere, migrating. If it is spring or fall, the great pivot points of the year, then the continents are swarming with billions of traveling birds..."

It is August 15th. Grasshoppers are leaping, goldenrod is blooming, indigo buntings are visiting my feeders, and some of the birds that summer in Minnesota and parts north will begin migrating soon. A great tide of birds will wash down from the north, moving down the Mississippi river towards the southern US, the Caribbean, Mexico, and Central and South America. They will fly over cities, counties, states, provinces, precincts, districts, and nations - a patchwork of histories, languages, cultures, religions, economies, shared experiences, and beliefs - with no passport or knowledge of boundaries other than those imposed by landscape and weather. What has that tiny indigo bunting at my feeder seen? How many miles have passed beneath its wings? What is it like to be an artic tern, which flies about 44,000 miles per year and experiences nearly perpetual daylight as it travels from Greenland to Antarctica and back again? What pulled D1 north 920 miles to Hudson's Bay every summer and what did it feel like when the fishhook of dispersal started tugging her away from the only world she had ever known?

There are a lot of reasons that birds are important. They connect people with nature, which gives us a reason to preserve the landscapes they need. They contribute important environmental benefits, including insect and rodent control, pollination, and seed dispersal. They are an important part of our economy, generating about $500 million annually in direct hunting revenue in my home state of Minnesota alone - and that doesn't count the money spent by birds, bird banders, and people who attend birding festivals. But to me, the most fascinating part of birds will always be their mystery. I am grateful for the window into their world that technology has given us, and for treaties like the Migratory Bird Act to help protect them as they wing their way through our world.

A brief history of three Acts that protect Bald Eagles
The ornamental plume trade provided the catalyst for two of the three Acts that protect bald eagles. In the late 1800s and early 1900s, hats decorated with plumes and other bird parts were a must-have for fashionable ladies. How bad was the plume trade? In February 1886, a young New York ornithologist named Frank Chapman set out on expedition to uptown Manhattan, counting the number of ladies' hats adorned with feathers and other bird parts. Over the course of two trips, Chapman counted 542 hats adorned with 174 whole birds or their disembodied parts. In Chapman’s assessment forty different bird species were represented in his count. As Lapham's Quarterly pointed out, this made uptown Manhattan one of the most diverse bird-watching territories in the world. It is estimated that over 5,000,000 birds were being killed annually to decorate hats and clothing.

Hats decorated with ornamental plumes were a must-have for fashionable ladies! 
Woman wearing a "Chanticleer" hat 
made of bird feathers, circa 1912.
Opera singer Emmy Destinn 
wearing a plume-covered hat, around 1909.

The Lacey Act and the Migratory Bird Treaty Act were passed largely to regulate and combat the ornamental plume trade, which decimated bird populations and drove a number of species to extinction. The Lacey Act, passed in 1900, was the first federal law protecting wildlife. It prohibited market hunters from selling poached game across state lines and was designed in part to stop the flow of feathers from the American countryside to the great millinery centers of New York and London. Iowa fans can be especially proud, since the Act was introduced by Iowa Congressman John Lacey.

The Migratory Bird Act was a landmark agreement signed by the United States and Great Britain in 1916 with the goal of 'preserving those species considered beneficial or harmless to man'. Like the Lacey Act, it provided a tool to limit the extensive ornamental feather trade and the unregulated shooting of birds. Both the US and Great Britain (acting on behalf of Canada, which was part of the British Empire) realized that international treaties were necessary to protect animals with no international boundaries. The two countries agreed to stop all hunting of insectivorous birds and to establish specific hunting seasons for game birds.

The Migratory Bird Act agreement was implemented two years later with the passage of the Migratory Bird Treaty Act of 1918. The act established penalties for people who broke the law, making it a crime to pursue, hunt, take, capture, kill, or sell a migratory bird or any of its parts, including nests, eggs, and feathers. This effectively shut down the ornamental feather trade and gave species like the snowy egret a change to rebound.

Breeding plumage: Far better on the snowy egret!
By Len Blumin from Mill Valley, California, United States (Snowy Egret display) [CC BY 2.0 (], via Wikimedia Commons
While bald eagles were covered under the Migratory Bird Treaty Act, they hadn't been directly affected by plume hunting. But sport shooting, bounty hunting, and habitat loss were another matter. The Bald Eagle Protection Act was enacted by Congress in 1940 to protect the bald eagle from direct hunting and habitat encroachment. As the territory of Alaska demonstrates, we haven't always admired bald eagles. Between 1917 and 1952, 128,273 bald eagles were killed and submitted to the Alaska Territorial Treasurer for bounty. We have no figures for the amount that were simply killed offhand or to provide feathers and parts for the trade in "authentic" Native American artifacts, but Congress felt that an act was needed to protect the bald eagle from extinction. The Golden eagle was added in 1962, amending the law to the Bald and Golden Eagle Protection Act.

While there are many complicated issues around the Migratory Bird Treaty Act (consider the controversial proposed bald and golden eagle take proposed by the Fish and Wildlife Service) it has saved millions if not billions of birds since the initial treaty was signed in 1916. Let's celebrate the act and keep moving forward to save birds for the next 100 years! Migratory birds need our help: as Steve Holmer, Senior Policy Advisor for the American Bird Conservancy, pointed out: "Forty percent of all migratory bird species are in decline, so it is urgent that we put in place practices we already know will save birds from needless deaths.”

The Fish and Wildlife Service has a long list of important conservation messages. I chose my favorite ones to post here! Remember, times change, and threats change with them.

What is the main threat to migratory birds? 
  • Habitat loss due to urban development, agriculture and other human activities is the main threat to migrating birds. [Note: 'other human activities' is probably referring to global climate change].
  • Migratory birds depend on suitable breeding and wintering grounds and stopover sites where they can rest and feed along their migratory routes. The loss of any sites used by the birds during their annual life cycle could have a dramatic impact on their chances of survival.
What can we do about it? 
  • Conserve habitat - conservation works! Where we have invested in healthy habitats, birds are doing well. Healthy birds mean healthy forests, wetlands, grasslands, shorelines and oceans [and healthy forests, wetlands, grasslands, shorelines, and oceans mean healthy birds].
  • By conserving birds we conserve our American landscapes and the economies and ways of life that depend on them. From farmers and ranchers to outdoor recreationists to children, we all benefit when birds thrive.
#birdyear #thenext100years

Friday, August 12, 2016

Eagle tracking: can you do something about the tracking antenna?

We were asked a lot of questions about eagle tracking during After the Fledge. D1, D14, Four, and D24 and D25 are part of a study by biologist Brett Mandernack from Eagle Valley: the first and, to date, most extensive tracking study in of free-living eagles in the Upper Midwest. Brett’s transmitter and field research have collected a wealth of data about the migratory, wintering, and summering behavior of bald eagles.

The most commonly asked question involved the PTT antennae located on the eagles’ backs. Could they be removed or shortened? How do the transmitters work and why are they the length they are? This blog attempts to answer those questions. Warning: it requires a fair amount of reading and has a long resource list at the end!

Can you get rid of the antenna?
We cannot. An antenna is needed to transmit data from the PTTs worn by our eagles. The PTT and GPS units from Geo-Trak Inc. collect and encode data about location, heading, speed, time, activity, and transmitter and battery performance. The encoded data is supplied as energy to the antenna, which radiates it as UHF radio waves to the Argos satellite network orbiting 528 miles (850 kilometers) over our heads. From there, ground stations receive real time data from the satellites and retransmit it to regional processing centers where we can access it. No antenna = no data.

Why can’t the antenna be smaller? Couldn’t it be part of their leg bands?
Let’s start with a quick primer. When we talk about radio waves, we are really talking about a small part of the electromagnetic spectrum - the range of all types of electromagnetic radiation (EMR). EMR is classified by wavelength into radio wave, microwave, terahertz (or sub-millimeter) radiation, infrared, the visible region that we perceive as light, ultraviolet, X-rays and gamma rays.
Our transmitters are talking from eagles on the ground to satellites in space using radio waves with a frequency of 401.664 MHz.  As the chart above shows, the higher the frequency, the shorter the wavelength. The shorter the wavelength, the smaller the antenna. So if a higher frequency means a smaller antenna, why aren’t we broadcasting at, say, 30GHz – the top end of the radio spectrum? An organization called the International Telecommunication Union coordinates the shared global use of the radio spectrum, which includes assigning radio frequency allocations for space communication. 399.9 - 403 MHz is the band that ITU has allocated for navigation, positioning, time and frequency standard, mobile communication, and meteorological satellites. Geo-Trak’s satellite tracking products use the Argos satellite network, which transmits and receives data at 401.650 MHz (± 30 kHz). Argos is using the highest frequency available to them.

So why does frequency impact antenna size? The wavelength of a frequency is the distance an electromagnetic wave travels to complete one cycle. As the image at right shows, a 401.664 MegaHertz signal (a signal that oscillates, or moves through a complete cycle 401.664 million times in one second) has a full wave length of 29.38 inches, a half wave length of 14.69 inches, and a quarter wave of 7.34 inches.

For the antenna to radiate properly, it needs to match either the full wave or one of its major harmonics. Therefore, 7.34 inches – a quarter wave - is as short as the antenna can be and still function. Perhaps improvements in materials, circuitry, and/or manufacturing will someday allow smaller antennae to be used in satellite tracking, but for now, a whip antenna is our only choice for robust ground to space communication.

The image at left shows an electrical wave oscillating through a full wave antenna, where the antenna is the same size as the wavelength. If the antenna were longer or shorter than the wavelength it is propagating, it would work less efficiently or not at all. A dipole antenna breaks the wave into two pieces, so it can be half as long as a full wave antenna. A quarter wave antenna - the kind used on our PTTs - breaks the wave into four pieces and can be a quarter the length.

I found the distance traveled to be quite fascinating. If you do the math, 29.38 inches (the distance it takes for our signal to complete one cycle) multiplied by 401,664,000 cycles per second equals roughly 186,000 miles per second. It takes a lot less than a second for messages to travel from the Dynamic Duo (D24 and D25) to the Argos satellite system 528 miles overhead.

Will electromagnetic radiation of an antenna hurt the eagles?
No. Terms like electromagnetic radiation are frightening, but not all electromagnetic radiation is harmful. Innately dangerous electromagnetic radiation is found in the high-frequency end of the spectrum, since high frequency waves are a lot more energetic than low frequency waves.  Think of it this way:  gamma rays have frequencies of 1 x 1021 Hertz, which means that the wavelength crests, or hits its highest potential energy point, 1 sextillion times or cycles per second. That packs a punch! By contrast, visible light has a frequency of around 5 x 1014 (500 trillion cycles per second), microwaves have a frequency of 1 x 1010 Hertz (ten billion cycles per second), and our radio waves have a frequency of 4 x 106 (400 million cycles per second).

Power is also a factor. I have a 1500-watt microwave oven that can damage living tissue. However, it is literally almost 7000 times more powerful than the 225mW solar units that power the transmitter. Even cellphones produce radio waves that are more powerful and energetic than ours.

What about insect studies? Those antennae are really small!
A lot of really cool work is being done with insects. While some of the technologies involve active transmitters, which require batteries, others use passive devices like RFID tags and geolocators. Passive devices don’t require much power and can be made extremely small. A couple of links:
Unfortunately, passive devices can’t transmit. Researchers don’t get data unless the animals move in close proximity to a reader (think of a feeding station where animals might gather), or they are recaptured for a data download. Geolocators could be used to track migratory peregrine falcons that return to the same nest box year after year, but they aren’t a good fit for tracking juvenile or sub-adult eagles that wander unpredictably and often widely.

The tiny little transmitters used in tracking insects are very cool – check out that tiny backpack! – but they have short battery lives (7-21 days) and a limited tracking range on the ground only (100-500m). As neat as they are, they aren’t suitable for tracking juvenile and sub-adult eagles either.

In short…
We can’t get rid of the antenna, which is as short as it can be given the frequency of our ground to space transmission. Argos did a great job designing a package that is light, safe, reliable, and trackable almost anywhere on earth, especially given the physical requirements of the transmission system. The transmitters do not harm bald eagles or impact their social or reproductive interactions with eagles that aren’t wearing transmitters. Passive devices aren’t a good option since juvenile and sub-adult eagles range unpredictably and often widely before settling down to nest, while tiny active devices have short battery lives and a limited ground-only tracking range – something that won’t work for animals that can fly hundreds of miles and live relatively long lives.

However, research into insects and small birds is driving tracking devices to become even smaller.  If at some point appropriate tracking hardware becomes available with a smaller antenna, we will use it.

Did you know?
The wavelength and frequency of electromagnetic waves are closely related. If you have a frequency, you can get the wavelength, and if you have a wavelength, you can get a frequency. With the wavelength, you can determine the length of the antenna you need to transmit or receive radio waves at a given frequency. The formula looks like this:  Wavelength = Wave speed/Frequency.

Let's say that I have a frequency of 401.664 MHz, or 401,664,000 cycles per second. The wave speed is the speed of light, which can be expressed as 3x108 m/s or 300,000,000. If I divide 300,000,000 by 401,664,000, I get .7468 meters. Since I was raised in the English system, I immediately convert it to inches or feet, which gives me an antenna length of 29.38 inches. This was very helpful when trying to determine why the antennae on our PPT systems are the length they were. This web calculator provides lengths for half and quarter wave antennas if you want to play around with making them:

What could you do with an antenna? There is a community of people that listen to the earth via homemade VLF radios. This website provides an introduction to the concept and some online streams:

Resources that helped me learn and write about this:
Since you made it to the bottom, I hope you enjoy this bonus image. XKCD explains the spectrum as only they can!