Why retrieve a deceased eaglet
Like a root canal or buying new gutters, sometimes we do unpleasant things because a lot of good comes from it. This story falls into that category of unpleasant-but-good events. With proper permitting, we retrieved a dead eaglet from an eagle nest, and we learned a LOT from what we found.
A few of the BENW volunteers in southeastern Wisconsin, from left to right Ginni, Beth, Ken, and Zach.
My husband, Ken, and I, along with a few friends, have been part of Madison Audubon’s Bald Eagle Nest since 2021, but we have been enraptured with and watching Bald Eagle nests for years. We have been relatively lucky with our BENW task, until this year. In normal years, we see a lot more successful nests than failed nests. Usually we watch a dozen or so young eaglets fledge from the nest and join the avian community. Yes, there are horrible storms that take out trees and nests, adults and young consuming lead poisoned animals, or extreme temperatures that are too much for the eggs or eaglets to survive, but mostly, eaglet nest watching was fun.
However, in 2022, our program saw a huge increase in failed nests. Concurrently, the new strain of Highly Pathogenic Avian Influenza (HPAI; also known as H5N1, avian influenza, and bird flu) swept through the country, a very infectious disease that can be tough on adults but seems to be lethal for young eagles. Like COVID-19, experts say that HPAI is not going to go away this time. We likely have a new normal and it is bleak when compared to previous years of increasing Bald Eagle reproduction in Wisconsin. However, we can learn a lot from this latest outbreak, and some of it is actually good news!
As eagle lovers, my husband Ken and I are constantly scanning the treeline as we drive. One day in March, we were lucky enough to spot one of the first Milwaukee County eagle nests. Were we the first to see it? No way. But we knew who to call and it became a nest that we watched through Bald Eagle Nest Watch, which branched out into us watching the other two Milwaukee County nests. Prior to 2022, Milwaukee County hadn’t hosted an active Bald Eagle nest since the 1970’s—so to suddenly have three in the county was fantastic!
An adult on the new Milwaukee County nest. Photo by Beth Martin
One of these nests was in Milwaukee County and Milwaukee City, which we referred to as MKE MKE (MM). We try not to pick favorites, but MM became a favorite of ours for a few reasons, all relating to our love for an unlikely success story:
They were a young couple. She still had a number of brown feathers where white should be and she had a brown and yellow marbled beak, instead of the bright yellow of a typical adult. He had a side of his beak that was mostly brown. So we knew they were subadults on the verge of being adults.
Their nest was small and seemingly not big enough for nesting
March 15 had come and gone, and they were not on the nest. That date is generally when all eagles are incubating if they are raising young during the current season.
Female eagle from MM nest. Photo by Beth Martin
But these eagles were not interested in rules and “usually”s. Homeowners had seen them copulate. The nest did get a bit bigger, and by March 22, Ken and I knew they were on eggs – there was a palpable change in the nest, with adults doing more sitting and general quietness. By March 23, we had our proof. We observed one of the adults rolling an egg! While we can’t see into the nest (and drones are extremely disruptive to eagles), we knew the body language to look for, and that day we saw it! We were so happy for them and so encouraged by their perseverance.
Around this time, we witnessed some odd adult eagle behavior at a nest near our home in Walworth County that was abundant with waterfowl, where the raptors were securely on eggs several weeks earlier. But on one of our last visits, things were not right and it was clear the nest had failed. The adults were behaving oddly, near the nest but not in the nest tree. If there were eggs or young chicks in the nest, the adults would be incubating, and leaving the eggs for no more than 15 or so minutes at a time. It was a peculiar behavior to witness. This was the first of our failed nests for 2022.
Entering the first week of April, a second, different nest in Milwaukee County had hatched! New chicks were being fed and all seemed well. But a short time later, it was clear that we once again had a failed nest with adults near the nest tree, but not in it or the nest. At the same time a female adult eagle who was building a nest on the south side of Milwaukee was stricken ill and unable to fly off the ground. She was caught by the Milwaukee Humane Society and taken into care for about 24 hours, before she was euthanized due to her advanced neurological HPAI symptoms that had her struggling to draw breath.
Ken and I saw a pattern. We noticed this at another nest we observe in Racine. The adult eagles were both a short distance from the nest, but not looking into the nest. It had failed as well. This was also true for another nest in Walworth County near the town of Whitewater.
An adult eagle looks away from a failed nest. Photo by Beth Martin
Depending on the article, one could believe that coming into the slightest contact with this new strain of Avian Flu was a 100% death sentence to raptors. Drew Cashman, Brenna Marsicek, and I had many dialogs trying to understand what we were seeing at the early stages of nest failure, since most of them were occurring in our neck of the woods in southeastern Wisconsin. But were we still seeing adults? Yes, thus far. But knowing an adult died from HPAI made it terrifying that we could start losing bonded pairs of eagles.
In an effort to understand and clarify what we were seeing and to understand how deadly the virus was to our eagle and raptor population, I wrote to The Raptor Center in Minnesota. They were testing every bird that came into their facility for care, whether they were presenting symptoms or not. The veterinarian was very helpful with suggestions, dissuaded the opinion that the virus was 100% deadly, and recommended that we get assistance from the DNR to retrieve and test eaglets that had died in the nest.
“Yes, HPAI can spread vertically from adults to eggs/chicks. I have not heard the statistic that HPAI kills 90-100% of the infected raptors. It is likely some/most individuals survive this panzootic of HPAI. There are so many variables - species, age, overall health, previous exposure to LPAI (remember waterfowl almost always carry this virus), the viral load, local climate, their genes, and ???. Since you are not seeing the loss of adults, perhaps the genetic make-up of the eagles in your area are 'related' and 'more resistant'...” - The Raptor Center
We continued to hold out hope for the MM nest, and by April 27, they were feeding chicks! This young pair of adult eagles had done it! They hatched two lovely chicks that were visible for the first time on May 4th. We were so pleased with what we were seeing. We have never seen such a young eaglet before.
The first look at the chick in the MM nest! Photo by Beth Martin
Feeding chicks at MM. Photo by Beth Martin
On May 18th, Ken and I ended up being part of the eaglet rescue in Sauk City. If you haven’t read Erin’s account of it, you can read it here. It is well worth the read.
On May 22, we went to check on MM and saw the same stance of the male adult, standing with his back mostly to the nest on a tree adjacent to the nest. Periodically, he would look down at the nest. The female was nowhere to be seen. We knew within seconds the nest had failed, but waited over 3 hours to see any feeding or tending to the very young chicks. They would have been between 3-4 weeks old and still that cute light gray fuzz. Eventually, the male adult flew off and we did not see it during the next hour we watched the nest. We do not know when they returned.
We contacted Drew and Brenna and told them we knew the nest had failed, in a similar pattern to the others that we suspected were due to HPAI. Was this our opportunity to retrieve a body for testing, and to know for sure if HPAI was the cause of 2022’s high nest failure rate?
With Drew trying to find approval to access the nest, I secured an arborist who I felt could handle the grim task ahead of climbing to the nest and retrieving the bodies. He could meet us at 5pm the following day. But time was ticking away, and the following day with just one hour to spare, we heard from the DNR and were given approval to proceed. So we jumped in the car for the hour-long ride to the nest, filling in Drew and Brenna on the way. A Wisconsin Department of Natural Resources Warden in Menomonee Falls was located and could meet us.
We all arrived at the nest location and our arborist was prepared with gloves and a face mask. We brought extra masks, gloves, and plastic garbage bags for him to bring up so that he would not have to contact the bodies with bare or gloved hands. His first priority was – and rightly – to protect himself. If he felt he could not climb the tree for any reason, this mission was off. But he assessed the tree as safe to climb. He would take photos as he progressed and send them to us below, so we could see what was happening in the nest.
None of us – 2 homeowners, the arborist, the warden, Ken or I – could have guessed what he’d find.
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The arborist took some time to properly secure himself at nest view level, to be able to use his hands to take photos, relay information and hopefully secure us the two bodies. But a surprise awaited him. After sending photos to us, it was clear that there was only one eaglet body remaining in the nest. The second eaglet was gone, and we could not locate it on the ground or anywhere in the tree. The eaglet body that was in the nest was headless, but not bloodied. The body was intact. In the nest with it, was a mostly consumed body of a Mallard hen. An indication of where Avian Flu had come from, if indeed the eaglet had died from or had Avian Flu. But why was it headless and where was the other body? After talking with the warden and other biologists, they confirmed it was most likely the work of a Great Horned Owl. (Which then led to concern that the body of eaglet would likely infect the owl and their nestlings with HPAI as well. But, that couldn’t be helped at this point.)
The body of the eaglet in the nest was still warm and had no rigor mortis setting in, indicating that it could not have been dead for more than 8 hours. Some folks thought the nest failed because the eaglets had simply been predated. But after hours of carefully watching the adult eagles, we knew these parents would never allow Great Horned Owls to have easy access to the nestlings. They were both always present at the nest except when one went to get food or nesting material, and the other remained behind. These were exceptionally attentive parents.
Scattered mess in the nest. Photo provided by the arborist on site
The eaglet’s body and that of the Mallard hen had been retrieved by the arborist and were then examined by the Warden and sent in for HPAI testing.
On July 21, 2022, we received the answer. The eaglet did indeed test positive for HPAI. Whether the eaglet died from HPAI before the Great Horned Owl got into the nest, it does not really matter. The eaglets were dying and would have died from the avian flu.
This information is so valuable. When the BENW program reported a 49% nest failure rate in 2022, which is more than triple the five-year average for the program, we knew we had to help understand why. This is why we participate in citizen science programs, after all — to help study trends and “events” that would otherwise leave scientists wondering. The work put into retrieving this eaglet body from the nest was challenging, but it helps advance part of the story of what happened in the bird world in 2022, and gives us a bit of information to build on for future years.
We cannot say all such failed nests from eaglets mysteriously dying were due to HPAI. There are other ways for eaglets to die in the nest… such as lead poisoning, consuming animals that were poisoned by homeowners or farmers, predation, etc. But many nests did follow the pattern of failure at MM.
So, what about the adults? Fortunately, the MM adults — as well as other adults from nests in the BENW program that our fellow volunteers reported as failed — have been seen as recently as late July. The Mallard hen that was partially eaten in the nest was likely consumed by these adults, meaning they likely carry some of the HPAI virus load. I wonder if it’s possible for adults to get HPAI, survive it, and pass on resistance to future clutches of eaglets… and if I ever find out, I am sure we will share that answer with you.
The two chicks, a few weeks later. Photo by Beth Martin
Regardless of the answer, I hope you’ll join me in raising a glass to those two adorable eaglets that did not live to grow up, but gave us some knowledge to carry forward into new eagle breeding seasons.
Written by Beth Martin, Bald Eagle Nest Watch volunteer
Cover photo by Beth Martin
