population decline

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Don’t tell me it never rains in southern California. I just spent Sunday morning getting drenched while hiding under an umbrella in Huntington Beach. My task: walk a concrete flood channel — we Californians call them “rivers” — while trying to protect my binoculars from a steady downpour and identify every soggy bird I could find along the waterway. Why would I subject myself to these miserable conditions? I was a proud participant in the Coastal Orange County Christmas Bird Count. (The photos above show: 1) me with another damp colleague on the count team, and 2) a rare reward that I got after birding on the Newport Pier.)

To those unfamiliar with them, Christmas Bird Counts (CBCs) are all-day bird censuses that take place within 15-mile diameter circles. Hundreds occur each winter. Each count happens on a single day between December 15 and January 4th. The location of each 15-mile circle is fixed; that is, observers count the number of every species of bird they see or hear within exactly the same count circle each year. And observers keep close track of how many people are out watching birds, over what distance they travel, and for how long, in order to have a record of how much effort was spent on the count. 

Why go out in cold, wet weather to count birds — sacrificing time that could otherwise be spent gift shopping, visiting with family, or arranging seasonal greenery in our homes? Because CBCs have become an important tool to track bird populations. If you count birds meticulously in the same area, in the same way, and for many years running, then any differences that you detect in counts between years are likely to reflect real population differences. Christmas Bird Counts have been used to document increases and decreases in the numbers of different species of birds over time and also expansions or contractions in the species’ geographic ranges. In short, CBCs produce useful scientific information; they are not just an excuse to dodge awkward political conversations with your brother-in-law over the holidays.

Of course, birdwatchers are insatiable. CBCs are just a slightly more glamorous and rigorous version of what birders do on their own throughout the year. That is, hundreds of thousands of birdwatchers in North America cover every nook and cranny of the continent, keeping track of the date, time, and number of each bird species they identify from January 1st to December 31st.

In recent years, Cornell Laboratory of Ornithology has sought to collect the information gathered by birders on their outings. No longer do most birders scribble down what they have seen in notebooks that get old and musty in a closet somewhere; they submit them to eBird, CLO’s online database. The eBird folks make the data that birders submit on their phone available to all others online and also analyze the data to infer changes in the abundance and distribution of birds. eBird has quickly become much beloved by birders as a way to keep track of and share their bird sightings. Because of eBird, we birders are no longer outright lying when we stride pompously towards the door, grasp the handle, and announce, “I am going out to do science!”

What does all of this have to do with loons? Loons appear on birder’s eBird checklists just as other birds do, of course. Because they are confined to territories, it is awkward to track loon breeding populations via eBird checklists. (Furthermore, the Breeding Bird Survey already does that.) But since birders from across the continent submit their birding results to eBird throughout the year, we can get a sense of loon population trends during winter from eBird data.

I was, of course, very excited to see the population patterns that eBird shows for loons. First, though, I wanted to see what trends showed up in eBird data from other species that popped into my head. The picture is mixed among the several land birds that I happened to check. Downy Woodpeckers, it turns out, have been increasing substantially in the past decade throughout North America. So have Red-bellied and Pileated Woodpeckers. Northern Flickers, on the other hand, have been declining across the continent since 2012. Among thrushes, Hermit Thrushes are down throughout the range; Swainson’s Thrush populations are down in the east and across the Prairie Provinces but increasing along the Pacific coast from Alaska southward to Washington state.

Looking at population trends among aquatic birds that share northern lakes with loons reveals a mostly bleak picture. Double-crested cormorants are declining almost everywhere within their range (with a few exceptions). Hooded Mergansers show declines in wintering populations along the Atlantic coast and southeastern U.S. — except along the Mississippi River, where they have increased in number. Ring-necked ducks, which we see on shallow lakes in Wisconsin and Minnesota, are down in about 85% of all winter count areas covered by eBird data, but up in the remaining 15%. Canada Geese, on the other hand, are increasing almost everywhere in the northern half of the continent (including most of Wisconsin and Minnesota), but are sharply down in northern Ontario and Manitoba.

Having convinced myself that eBird is picking up both upward and downward shifts in bird populations and also exhibiting the patterns we have seen ourselves in familiar species like Canada Geese, I turned to winter trends in common loons from 2011 to 2021. As the figure shows, almost all coastal regions from the Atlantic to the Gulf of Mexico show a decline of between 20 and 30% for this period.* There are a few exceptions — chiefly inland reservoirs, in which perhaps 2 to 3% of all loons winter — most of which show increased numbers of loons seen in winter. (The tiny widely scattered blue dots indicating these increases represent very small populations and are hard to see in the figure.)

Trends in wintering populations of common loons from 2011 to 2021. From eBird online.

If you are seeing red after studying this map, join the club. It is not a pretty picture. Winter ranges do not map onto breeding regions cleanly, so it is a bit difficult to infer population trends in breeding areas directly with this figure. However, the fact that wintering loon populations are declining everywhere in North America — even along the Pacific coast, not shown here — suggest that common loon populations have fallen broadly.**

What about Wisconsin and Minnesota? If you have followed my blog for awhile, you probably recall that loons from both states winter primarily along the entire Gulf Coast of Florida and that the remaining 20% winter in the Atlantic from Carolinas southwards. So the entire wintering range of Upper Midwest breeders is covered with red dots indicating 10 to 40% declines over the past decade. While it is important to remember that loons from other breeding populations — notably the massive Ontario and Quebec populations — winter in these coastal regions also, this across-the-board pattern is disturbing. It is, of course, consistent with what we have documented in Wisconsin and what others have documented in Minnesota.

How do we respond to this new piece of bad news about the common loon population as a whole and in the Upper Midwest? Do we fold up our tents…throw up our hands…throw in the towel? No, indeed. We get busy. Multiple problems that loons are facing and that impact the population negatively are fixable and must be fixed. So we get back to work.

WATER CLARITY GOAL

As stated on our Current Goals page, we are currently probing the loss of water clarity that is harming loon chicks to learn precisely what is making lakes less clear by testing three main hypotheses:

  • water clarity falls after rainfall because of dissolved organic matter that washes into lakes.
  • clarity declines as a result of suspended sediments carried into lakes by rainfall.
  • the decline in clarity comes because of fertilizer, waste and other human-related substances from lakeside lawns, which spawn algal blooms.

By pinpointing what is causing the loss of water clarity, we can call attention to the problem and urge state and local agencies to take action to curb it.

WINTER OCEAN CONDITIONS GOAL

We will also continue to investigate negative impacts of Florida ocean conditions on Upper Midwest loons through statistical analysis using a large long-term dataset from Tampa Bay. If deteriorating ocean conditions during winter are driving our loon population downwards, we would like to learn that now, leaving ourselves time to identify the problem precisely and — through publicizing our findings and working with state and local water quality agencies — attempt to turn things around.   

CAN YOU HELP US?

We rely solely upon private funding to support our vital fieldwork in Minnesota and Wisconsin. Our teams — wildlife students and myself — collect data throughout the summer to address our goals. Funds never go for my salary; I am paid by Chapman. Rather, funding that we receive from you supports: 1) small monthly stipends for our student workers, 2) lodging for students and me, 3) travel costs to, from and within our study areas in Minnesota and Wisconsin, and 4) supply and equipment costs (canoes, binoculars, banding supplies, and other miscellaneous items).

Thanks for any support you can give us as we work to protect Upper Midwest loons.

DONATE TO THE LOON PROJECT

* You may look at the trends reported by eBird yourself by: 1) going to their site; 2) scrolling down and clicking on “eBird Status and Trends”, 3) entering a species name, 4) grabbing and spinning the world around to see North America, 5) clicking “Trends”, and 6) zooming in and panning, as needed, to see the region you wish to see.

** This figure suggests that loon populations are falling across the breeding range. Yet we know that there are pockets, like Vermont and perhaps other portions on New England, where loon breeding populations are either stable or up in the past decade. Therefore the falling loon numbers shown for the Northeastern Seaboard must mean that other breeding populations — perhaps the very large ones in Quebec or the Maritime provinces — are responsible for the decline.

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I have started to call it “the Great Void”. It is the period between a chick’s first autumn and the point — at 2 to 4 years of age — when it has matured, molted into adult plumage, and returned to the breeding ground to look for a territory. Why “void”? Because we know almost nothing about loons during this period.

The Great Void used to be a nuisance. It was frustrating to think that our birds were passing through so many critical life stages without us knowing where they were or whether they were alive. But we have now pinpointed high mortality of young adult loons as the greatest threat to the loon population of Wisconsin and, more recently, Minnesota as well. “Nuisance” no longer captures the depth of our frustration. We now have to admit that we know least about our loons during the time when it matters most. So I think we need to begin to describe the Great Void as a grave concern.

Yet we are not completely in the dark. We get a glimpse into the Great Void now and then. Here is the story of one glimpse we got in March of 2024 from the wintering grounds.

As soon as he spotted it, Jim “Crater” Anderson could see the bird was in trouble. Seabirds in Panama City, Florida do not lounge on the beach in late afternoon sun like tourists from Ohio. And this one was looking especially out of sorts. It was well above the high tide point, sitting in dry sand. Crater did not think twice about interrupting his daily 10,000 steps to come to its aid.

“That is not how a duck should sit”, Crater thought, looking at the bird. Indeed, with legs splayed right and left of its body and belly in the sand, it was a curious sight. The animal skootched awkwardly across the beach and flapped frantically as he approached to within five yards, making him wonder if its legs were broken. At that moment, he felt strongly that he must capture the bird and take it to someone who could help. He removed his grey hoodie and, crouching low to the ground to appear less threatening, crept still closer. “It’s okay, I am going to get you to someone who can fix you up”, he murmurred reassuringly.

The bird was not mollified by Crater’s soothing words. Now that he was within six feet, it whipped its head around and eyed him suspiciously. He steeled himself and grabbed it, enduring its painful nipping at his arms and hands. As quickly as he could, he swaddled the bird in his hoodie to calm it and walked briskly to Rick and Sheila Harper’s house. “They have parrots”, he reasoned. “They’ll know what to do.”

The bird he was carrying was bigger and heavier than he had thought it would be – much larger than any duck he had handled. Its bill was thick and dagger-like. Its legs were not broken, just connected at the very end of its body. And – this was the biggest surprise of all — someone had placed four brightly‑colored bands on the bird’s legs. “What is that all about?” he thought.

When he arrived at Rick and Sheila’s, Kim Youngbeck was also there. The four friends placed the bird in a cat carrier that was snug but secure and set about trying to learn what kind of bird it was and how they could help it. Sheila’s parents are birdwatchers who live in Park Falls, Minnesota. She sent them some photos in hopes that they could help with the ID. “That’s a loon!”, they announced with equal parts excitement and concern.

The Florida Fish and Game contact they spoke to informed them that a loon would not do well in captivity and that they should return the bird quickly to where they had found it. Dutifully, the friends walked back to the beach. Night had fallen in the hour or so since Crater had first captured the loon. Knowing that coyotes and raccoons prowled the beach at night, they decided to place it higher in the dunes than it had been at first. That seemed safer.   

Still, they worried about the loon sitting exposed in the darkness. The bird had not tried to get away from them after they placed it back on the sand. And when they went back to check an hour later, it had not budged. At that point, Kimberly volunteered to take the bird for the night.

Back at home, Kimberly wracked her brain to think what was wrong with the animal. Was it weak from hunger? Knowing that its diet was mainly fish, she offered it the only fish she could – some tilapia filets from the fridge — on a small plate. The loon showed no interest. She looked at the clock and realized that it was 10 p.m. Whatever they were going to do for this loon would have to wait until the next day. She turned the lights out, draped a sheet over the carrier, and hoped it would get some rest.  

The next morning Crater and Kimberly strategized again about the bird. It looked pretty healthy and fiesty, they agreed. They could see no reason to hold onto it any longer. Together they decided to return it to the ocean.

The two friends took the carrier to the beach and removed the loon. This time, though, they let it go at the water’s edge, where the waves were breaking on shore. With furrowed brows and hands on hips, Crater and Kimberly watched as the bird bravely faced the waves and began to crawl towards the ocean. It was not pretty. On five occasions, a wave caught the loon and hurled it backwards several yards towards the beach. Kimberly was reminded of videos she had seen of tiny sea turtles heroicly battling the surf to reach the sea after hatching. The bird did not give up, however. Eventually it was able to take advantage of a lull between waves, reach water deep enough for a dive, and plunge beneath the crashing surf. Kimberly and Crater cheered to see its head pop up thirty yards from shore, well beyond the surf zone.

After a late March sojourn with beach-going humans, the loon, which we had banded the previous summer on West Twin Lake in north-central Minnesota, was back where it belonged — and looking none the worse for wear. We have no idea what brought this nine-month-old to shore.

We got a second, more sobering glimpse into the Great Void in late August 2025.

Battered by stiff winds and high waves from Hurricane Erin, the loon sat within the surf zone on Rockaway Beach in Queens, New York, twelve miles southeast of the Statue of Liberty. Waves crashed over it — even submerging it entirely on occasion. Susan Garman and her ten-year-old son Justin had made a quick trip to the shore to gawk at the surging whitecaps. But when they spotted a large bird that was being pummeled by waves and seemed unable to help itself, their light-hearted jaunt to marvel at nature’s fury took a serious turn.

They hurriedly shed their shoes, waded into the surf, and approached the bird. It looked as bad as Susan had feared it would: dazed, bedraggled, and water-logged. Worse still, the bird showed little fear of Susan and her son when they approached it. “You’re hurt, aren’t you?” she said to the animal, a comforting, motherly tone in her voice. “We are going to help you”.

Yet after she had gathered the bird up, Susan’s concern deepened. She had hoped to feel a smooth, reassuring mass of pectoral muscle when her fingers reached around its chest and belly, but instead, she encountered the sharp protruding keel of its sternum. So it was also emaciated. “Oh, buddy, I am so sorry!”, she whispered. It lifted Susan’s spirits slightly to see that the bird had four bright color bands on its legs. Her mind now racing, she reasoned that the person who had marked this bird would surely wish to help them save it.

She and Justin carried the bird to their home to do what they could. They nestled it in some blankets in the kitchen; it made no objection. Susan Googled “injured bird”, and found some local rehabbers and veterinarians, but no one that she reached could or would help. Justin submitted a photo of the bird to Google Lens to try and identify it. Lens came back with: “The bird in the image is a Common Loon.” “A loon!”, Susan repeated, trying to square her recollection of that glamorous northern species with the unsightly mass of soaked, tousled feathers on her kitchen floor. She and Justin were cheered by their ability to identify the bird they had rescued. They finally seemed to be getting somewhere.

But the loon was very weak and slipping away. “We are here with you”, was all she could muster, her voice softer and breaking from sadness and frustration. Finally, the loon stretched its head forward for a moment, pulled it back again to rest on its chest, and let out its last breath. Crushed by the loss herself, Susan looked for a positive to share with her distraught son. “At least it did not die alone”, she offered.1

We will have to record many more encounters of our young marked loons before we can shed much light on the alarmingly high mortality of loons during their first few years of life. Meanwhile, I am keeping my fingers crossed that other loons of ours who are in need of aid find such generous, compassionate people as these two youngsters did.

1 – We had banded the loon that Susan and Justin found as a chick on Upper Hay Lake, near Pequot Lakes, Minnesota, in July of 2024. So it was just over a year old when it perished. From the work of Kevin Kenow and his team, we know that loons from the Upper Midwest that winter off of Florida make their way up the Atlantic coast to spend the summers of their first and second years of life as far north as the Gulf of St. Lawrence. Thus, this young bird was probably on its way back to the wintering grounds in Florida.

Our paper on the Silver Spoon effect in loons has just been published online. You can read it at:

https://link.springer.com/article/10.1007/s00442-025-05836-8?utm_source=rct_congratemailt&utm_medium=email&utm_campaign=oa_20251124&utm_content=10.1007/s00442-025-05836-8

The top photo is of the loon from Panama City Beach, Florida. Photo by Jim Anderson.

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Following a long summer of capture, marking, and field observation, we have a new tranche of loon data from Wisconsin and Minnesota. The picture in Wisconsin does not change greatly from year to year. There we already had 32 years’ worth of research findings before 2025. But each successive year in Minnesota — where our research began in 2021 — increases our understanding of that population immensely. And with our improved knowledge of Minnesota loons, the status of the loon population across the Upper Midwest is coming into focus.1

Three demographic parameters together dictate whether a population of animals is increasing, decreasing, or stable, These factors are: 1) survival of breeding adults, 2) reproductive success, and 3) young adult survival. Recent measurements have shown us that the Wisconsin population is declining. And we know very well which of these parameters is responsible for the decline. If we compare our growing dataset in Minnesota to the trove of data we have from three decades of research in Wisconsin, we can learn whether or not Minnesota loons are headed in the same direction.

First, let’s look at survival of adult breeders. It should not be surprising that the most important single indicator of population dynamics (i.e. whether a population is stable, increasing or decreasing) is the rate of survival of its adult members. There is good news from the Wisconsin Study Area. The survival rates among territorial females and males both have been stable for the past three decades (Figure 1). This finding implies that once loons reach adulthood, they survive and hold their territories well. The decline that we are seeing in the Wisconsin population, then, must come about because of problems that occur before loons settle on territories.2

Figure 1. Annual survival rates of adult breeders on territories.

What about survival of territorial breeders in Minnesota? From measurements in 2022, 2023, and 2024, it appeared that adult survival in Minnesota might be lower than that in Wisconsin (look at these years in Figure 2, below). However, each year we get a better “read” on these numbers because our sample of loons becomes larger and more representative of the overall population. So the 2025 adult survival numbers are the most reliable ones we have to date. As you can see from Figure 2, there is no evidence for a

Figure 2. Survival rates of adult breeders in Wisconsin and Minnesota from 2022 to 2025. (Sample sizes are shown above each bar.)

difference in survival rates of territorial adults between Wisconsin and Minnesota. Minnesota, like Wisconsin, is seeing good adult survival. Again, this is good news!

Now let’s turn to reproductive success in the two states. Since we learned recently that the silver spoon effect is strong in loons, we know that we must look both at quality and quantity of loon chicks produced to get a good sense of how well a population is reproducing.

First let’s look at quantity. As Figure 3 shows, chick production in each region fluctuates greatly from year to year according to ice out date, severity of black flies, water clarity

Figure 3. Chicks fledged per territorial pair since 1995 in the Wisconsin Study Area and from 2021 to 2025 in the Minnesota Study Area. (Dotted line shows the trend in Wisconsin.)

in July, and other factors. Overall, however, chick production has decreased significantly in Wisconsin during the past three decades. Adult breeders are simply not producing as many offspring now as they did 30 years ago.

While Wisconsin data show a clear decline in number of chicks produced, it is too early to discern a trend in Minnesota. Chick fledging rate simply bounces around too much from year to year to see a pattern. We can say that chick production is at a similar level in the Wisconsin and Minnesota study areas. However, note that 2025 was a banner year for chick production in Minnesota and a poor one in Wisconsin.

Next we need to look at the quality of loon chicks that Wisconsin and Minnesota are producing. Our recent work has shown that chicks that fledge at low weights are much less likely to survive to adulthood and produce chicks themselves than are their heavier peers. Chick body condition has been falling for the past few decades in Wisconsin (see Figure 4, below).

Figure 4. Average body condition (mass divided by age) of chicks in Wisconsin from 1998 to 2025 and in Minnesota from 2021 to 2025. (Trendline shows Wisconsin pattern.)

The five years of data we have on body conditions of Minnesota chicks are not as many as we would like, but the numbers are consistent. Chicks fledge in Minnesota at similar — or even slightly worse — body condition than those in Wisconsin (Figure 4). We can infer that Minnesota is suffering from the same challenging chick-rearing conditions that have plagued Wisconsin (probably declining water clarity).

The third and final piece of the puzzle that we need to understand population dynamics is the survival of young adults. These birds are the breeders of the future that have not yet settled on territories. They range from three to about six years of age.

If you have been following my blog closely, you know that young adult survival of Wisconsin loons has seen the most dramatic decline among the three critical population determinants. That is, adult survival has held steady, and chick production has fallen somewhat, but the return rate of young adults to the breeding grounds has been abysmal — far below what it was a quarter century ago (see Figure 5, below).

Figure 5. Return rates of chicks to the breeding grounds 2 to 4 years after being banded as chicks in Wisconsin. (Data are missing for 2000 and 2007.)

We have been on pins and needles to see if this distinctive and rather alarming Wisconsin pattern is present also in Minnesota. Fortunately, our understanding of young adult survival has grown by leaps and bounds in Minnesota this year. Why? Because: 1) we started banding Minnesota chicks in 2021 and have done so every year since then, 2) most young loons return to the breeding grounds at three or four years of age in adult plumage, and 3) we regularly record identities of these young birds as intruders and loafers within our study areas. Thus, 2024 gave us our first glimpse at young adult survival in Minnesota using the crop of 26 chicks banded in 2021. And 2025 provided an even better window onto young adult survival there, since we could look at the return rate of 64 banded in 2021 and 2022 combined.

What do our findings show so far? In 2021, we banded 52 chicks in Wisconsin. Of these, 7 had returned as of 2025 (13.5%). We marked 28 chicks in Minnesota during 2021, and only one has so far been spotted as an adult (3.6%). For chicks banded in 2022, the numbers that have returned in Wisconsin and Minnesota, respectively, are 5 of 44 (11.4%) and 4 of 36 (11.1%).

These numbers tell a clear story. The percentage of young adult loons returning as adults in Minnesota is well short of that expected in a healthy population (a rate of about 41%). That percentage is also far below what we have seen in the past in Wisconsin (note the return rate in the 1990s and 2000s in Figure 5). In fact, the low return rate of young adult loons in Minnesota closely mirrors the dismal rate in Wisconsin.

In summary, it has taken five years to be confident of how the loon population in the Minnesota Study Area is faring. But our data now show that loons in Minnesota — at least those in Crow Wing and Cass counties, where we work — exhibit the same set of quirky demographic patterns that typify loons in Wisconsin and have set in motion a decline in the overall population there: 1) strong and stable adult survival, 2) poor reproduction in terms of both number of chicks and body condition at fledging3, and 3) a massive and diagnostic plunge in the survival rate of young adults (which are future breeders).

We have work to do.

1Thanks to Sheila Johnston, who took this photo of a molting adult loon on Gull Lake, which is just south of the Minnesota Study Area.

2I know. I just published a blog post in which I mourned the losses of many male breeders in the Wisconsin Study Area. I am still concerned about these losses. But in the long-term, which spans over three decades, adult males and females both have survived well. So I am hoping that the loss of several old, established male breeders this summer in Wisconsin was a blip.

3As noted earlier, it is too soon to tell from our data whether the number of chicks fledged is declining in Minnesota. We will gather those data over time. But we already know that Minnesota loon chicks are fledging in poor condition, just like Wisconsin loons. It is worth noting that the Minnesota Loon Monitoring Program, which has counted chicks across the state since 1994, reports a long-term and statewide decline in chick numbers.

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Loon calls seem to demand our attention. And sometimes they affect us emotionally. So it was this spring as I sat in a canoe with Sophia on the Blue Lake-West territory. While mopping up lakes after the pre-breeding census, we found the 16-year-old Blue-West female, W/G,B/S or “White-Green”, alone. Her behavior was ordinary, for the most part; she foraged, rested, and preened. Yet every few minutes, as if guided by an unseen hand, she lifted her head skyward and emitted a loud wail whose declining pitch seemed to convey profound and irredeemable sadness. Clearly her mate from the previous season was gone, and no male had stepped in to fill the vacancy. Indeed, White-Green spent the spring alone and still had found no partner in mid-June, long after the window for nesting with a new mate had closed.

White-Green was not alone in her solitude. On the following day Korben and I found the female on Hilts Lake, “White-blue-Silver”, nervously hanging out in the northwestern corner of that small lake. She foraged cautiously, unable or unwilling to drive off an intruder that foraged at will in her territory. She too found no mate with whom to breed this year. Having observed two openings for male breeders at the beginning of the year, I started to wonder if I was seeing a pattern.

I was chagrined to observe one of my favorite males, Green over Green, White over Silver (i.e. G/G,W/S or “Green-Green”) caught up in the male troubles that seemed to typify 2025. In 2015, when he took over Flannery, he created headaches for the resident female, who was rearing a chick on her own after losing her mate suddenly. But in the decade that followed, Green-Green became the steady, unflappable presence that his father was on Townline1. I smiled each time my schedule called for me to visit Flannery, knowing that I would get to check in on this tame, accepting male. But this spring, a few days after finding males missing on Blue-West and Hilts, I failed to locate Green-Green on Flannery. Instead, I followed his mate as she foraged throughout the lake. Every few minutes, she wailed pitifully — just as the Blue-West female had done. I took her behavior as a sign of Green-Green’s likely disappearance. A week later, however, Anna found Green-Green on Flannery behaving normally but reported that his left eye was cloudy. He remained on Flannery for the next month. But on July 13 he was found incapacitated by lake residents. Linda and Kevin Grenzer captured Green-Green and took him to REGI for treatment. Nine days later he seemed recovered and was released on Boom Lake. That was the last we heard of him until three days ago, when I got a report that his carcass had been recovered on the north shore of Washington Island on Lake Michigan. His presence there showed that he had recovered well enough to make a long flight east in preparation for his southward migration. We cannot be certain how he died, but his neck had a deep wound, which might indicate a prop strike. Life moves on, of course, but I am not looking forward to my next visit to Flannery, as I used to.2

The news was even more disheartening for the North Two male, “Red-Blue” (R/B,Ts/S). This tame 18-year-old loon — a veteran breeder that claimed the lake in 2014 — beached himself in early July. Linda and Kevin netted Red-Blue and took him to REGI also (see photo above, courtesy of REGI). He did not look terrible at capture, except that his right wing drooped. But he slid downhill rapidly and passed away within two days. The sudden appearance of necrotic tissue without other symptoms led REGI to conclude that he might have been electrocuted, perhaps through an ungrounded wire associated with someone’s dock lights. Naturally, his death was another blow. Despite the dearth of good nesting habitat on North Two, Red-Blue had raised four chicks during his eleven years on the lake.

Bad news comes in threes they say. So it was with a sense of inevitability that I learned recently of the third death of an established male during the breeding season in Wisconsin. G/S,Ar/Y (“Auric Red-Yellow”) was a skulker. My memories of Auric Red-Yellow are chiefly from capture nights. His was the ghostly black and white form that would take shape in the distance at night after we had motored slowly down sinuous, weed-choked Jersey City Flowage and spotlighted what seemed like ten thousand mallards lurking in patches of lily pads. But he was a successful parent, having fledged nine chicks with his even-more-skittish mate: Silver over Pink, Green over Green. Auric Red-Yellow was found dead on shore and emaciated, having ingested some form of metal. A vet must confirm this, but it seems that he swallowed someone’s lure, lost the ability to feed himself, and died of starvation.

Preoccupied as I have been with loon capture and marking, wrapping up the field season, and starting a year-long sabbatical, I have had difficulty processing the flurry of male mortality. I hope that the three males lost mid-season will be replaced by youngsters who had been waiting for their chance. After all, that is the way of things. Yet loss of male breeders does not always happen smoothly — or at all. The disappearance of our much-beloved male, Clune, from Linda Grenzer’s home lake in spring 2023 has resulted in three years (and counting) without a breeding pair on Muskellunge Lake.

In fact, I find this recent loss of five established male breeders profoundly unsettling. I have pointed out before that males are the limiting sex in loons. That is, males live shorter lives than females, and this tilts the adult sex ratio towards females. Put simply, males are in short supply, while there are ample females to fill breeding positions. Males have also been impacted by loss of water clarity. They, like chicks (and unlike females) are of substantially lower mass now than 20 years ago. As the “weak link” in the population, males seem most likely to be the cause of further population decline. Does the loss and lack of immediate replacement of these males this past season signal the beginning of that downturn? I hope not. But the pitiful wails of the solitary Blue-West and Flannery females after losing their mates made this year’s loss of males especially poignant and the memory hard to shake.

1Although there are many finalists for the honor, my all-time favorite loon was the old Townline male, Silver over Red, Orange over Green (S/R,O/G). “Orange-Green” was a doting dad who cranked out 20 chicks with five different females during an incredible 24-year run on his tiny lake just west of Rhinelander. Banded as an adult in 1994, Orange-Green seemed uncertain at first about his role on the Loon Project. Each time we launched our canoe and approached to take data he would eye us suspiciously for a moment and then relax, as if recalling that we were just those canoeists that liked to hang around with him and his family during the summertime. I was sad when Orange-Green did not return in 2018.

2The only good news to report regarding this episode is that another local male — this one an eight-year-old who was raised on Emma Lake and who made failed nesting attempts on Sherry and Hook lakes recently — is showing signs of claiming Flannery for his own and settling in with the breeding female. If he does so, the Flannery female — a pleasant, tame individual whom we banded as an adult in 2021 — will have no more reason to wail.

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Twenty years ago colleagues and I published a paper showing that artificial nesting platforms increase loon’s hatching success by 70%. Others have reported similar patterns. So there is no doubt that, on average, loons that incubate their eggs on artificial nesting platforms (“ANPs”) put more chicks in the lake than do pairs using natural sites. Moreover, our paper showed that greater hatching success produced by ANPs also leads to more fledged loons.

In the last two decades, ANPs have become an enticing tool used by loon conservationists to boost loon populations. This is not surprising. ANPs have proven to be effective, and they are rather easy to make and place in the water. So conservationists can plop a mess of ANPs in the water and feel pretty confident that they have added young loons to the population. And they can make a strong case to funding agencies that their actions might help loons avoid population decline. Indeed, many millions have been/are being spent in the U.S. to float ANPs as a means to mitigate the negative effects that oil spills in the Gulf of Mexico have had on the species.

Are ANPs really just as good as natural sites at producing young loons that reach adulthood? Or are platform-raised chicks not as likely to survive to fledging age as chicks hatched as natural sites? We must remember that loons pick the location of a natural nest, whereas humans choose the site where platforms go. So it seems quite plausible that platform-raised young face hazards that natural-raised young do not.

It is only now that I have large enough samples of nests from platforms and natural sites that I can run a head-to-head comparison. Despite my 32 years of Wisconsin data, only a small proportion of loons in the Wisconsin Study Area (e.g. 15 of 90 focal pairs in 2024; 17%) nested on platforms. In Minnesota, however, almost half of all of our focal pairs use ANPs (38 of 84 territorial pairs in 2024; 45%), so our sample of platform-hatched chicks has swollen markedly since 2021.

As the graph above shows, hatchlings from platforms are lost slightly more often than are natural-hatched chicks in both states. While the pattern shows up in both Minnesota and Wisconsin, the difference is quite small and does not reach statistical significance. In other words, we have no scientific evidence that chicks hatched on platforms suffer lower survival than those hatched at natural sites. The same can be said for chick loss in Wisconsin versus Minnesota, despite what appears to be a slightly higher rate of chick loss in the North Star State.

Frankly, I am relieved! It has become almost de rigueur to place an ANP in your lake to support the loons. If, for some reason, ANPs had been producing chicks likely to perish before reaching adulthood, it would have sent shockwaves through the world of loon conservation.

I am still not a great fan of nesting platforms. Why not? Because we have learned in recent years that nest predation is not the main problem loons are facing in the Upper Midwest. Remember, nesting platforms are a one-trick pony. They increase hatching success enormously and put more chicks in the water. But if chicks cannot get enough food to survive to adulthood or reach prime condition, then all of the platforms in the world will not help them.

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A few years ago, a team from Canada learned about the declines in loon populations that have been found by researchers in Ontario and Quebec and by us in Wisconsin and decided that it was time for a documentary. It took the company a few years to make the film available in the U.S., but now it is streaming on Peacock. The title is “Loons: A Cry from the Mist”.

One never knows how these pieces will turn out. The producer tells you that they want to interview you on such and such a date against this background and have you talk about this, that, and the other thing. Of course, you try to steer the interview towards topics that you deem most important. In the end, the producer and editor (I think) stitch together some of your comments and some comments of others to create the best possible story. You can only sigh to learn that your best quips ended up on the cutting room floor.

I cringed at a few aspects of the film. Like many others before them, these filmmakers could not resist the patently false idea that loons are ancient. Mercury, which has been studied for decades yet still has not been shown to have more than weak negative impacts on loons, is portrayed as a likely cause of the decline. The age at which loon chicks reach independence is stated incorrectly. And, of course, I wish I had worn a nicer shirt!

On the other hand, I was proud of how well the 2022 Wisconsin Team handled loon capture. Because of scheduling, filming could only occur on our very first night of capture. Yet Molly, Chris, Sarah, and Claudia shrugged off my nervousness and looked like seasoned professionals. The crew got some dazzling footage from Canada and our Wisconsin Study Area. Their profile of Linda Grenzer and her loon pair, Clune and Honey, is sweet and uplifting. I did not sound like a complete idiot during my bits. Most important, I was able to highlight the high rate of young adult mortality that we are seeing in Wisconsin and the need to understand that recent pattern.*

In short, Yap Films produced colorful, entertaining, and largely accurate loon documentary describing the concerns that conservation scientists have about the species. If you have 50 minutes free, it is worth a look!

*Of course, we now know that the decline results in large part because of poor feeding conditions early in life, which ruin a loon’s chances at a long, fruitful life. Too bad the film was not made a few years later!

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The Silver Spoon Effect occurs when individual animals that experience favorable circumstances early in life — like abundant food — enjoy long lives and produce many offspring when they reach adulthood. In essence, growing up well-fed places a young animal on a track to become successful as an adult.

The Silver Spoon Effect is strong in loons of the Upper Midwest. How do I know this? I have just done a massive analysis of factors associated with return to the breeding grounds among loons banded as chicks. I learned that chick mass (adjusted for age) is the single strongest predictor of both survival to breeding age and breeding success. That’s right: a loon’s mass as a chick accurately predicts how long it will live and how many young it will raise.

This does not mean that a loon chick that grows up without adequate food is guaranteed to die young and raise no chicks. Nor does it mean that a fat, healthy chick is certain to survive to adulthood and have many offspring. After all, it is a statistical pattern. But body mass in chicks is a very strong predictor of lifelong success. The graph below shows the effect.

Loons that did not survive to breeding age tended to be those with low mass as chicks (top row). Loons that survived to return to the breeding ground but never raised young (middle row) tended to be of intermediate mass as chicks. Loons that became successful breeders were mainly those that had been heavy as chicks.

It is hard to know how to feel about the Silver Spoon Effect. On the one hand, it seems cruel. One would love to think that a loon chick could overcome a rough start and turn its life around. But such a turnabout rarely happens. A juvenile that struggles to get enough food in its first month might make its first migratory flight to Florida. However our data show that such a loon has very low odds of surviving beyond its first few years.

On the other hand, loons reared with a silver spoon become the reproductive pillars on which the population’s persistence depends. Take the Pickerel-West male pictured in Hayden Walkush’s photo above. This male — “yellow over white-blue, auric red over silver” (Y/Wb,S/Ar in the table below) — was 8% heavier than average when we captured him on Tom Doyle Lake on August 3rd, 2013 with his parents and younger sister. He was then five weeks old. The momentum that his parents built for him gave him good odds of surviving to adulthood, settling on a productive territory, and rearing young himself. Indeed, he has already fledged six chicks on Pickerel with two different females despite being only eleven years old.

“Yellow over white-blue” is not exceptional. In the table below, you can see the list of all of our recent Wisconsin breeders that were marked as chicks. (Most are males because of the much shorter range of natal dispersal by males.) Pay particular attention to the right-hand column (“% above avg”). A “0” in this column indicates that this loon was of average mass for its age as a chick. If this were a random set of loons, the red numbers would all fall around zero; some a bit negative, some a bit positive. In fact, the table looks like something from Lake Wobegon: almost all territorial breeders in our study area were well above average mass at the chick stage. Sixty-five percent were absolute whoppers — 20% or more above average mass. This is a good illustration of the strength of the Silver Spoon Effect. (The pink-shaded cells show the few current breeders that were of below-average mass as chicks.)

Breeding lake, natal lake, band combination, sex, Chick Mass Index, and % difference from population average for current breeders in the Wisconsin Study Area.

The table shows something clearly. Territory settlers are the cream of the crop. Yes, there are a few overachievers — Harrison Flowage, Manson, Nose, Sherry, Silverbass and Soo. But their small number speaks to the strength of the pattern.

Leaving aside the fascinating and often brutal nature of silver spoons, let’s look at the implications of the pattern for loon conservation in the Upper Midwest. If you recall, the young adult “die-off” that we have found there is the most troubling aspect of the current population decline. Put simply, we are losing the vast majority of all young adults between the time they leave the breeding grounds as juveniles and return to it as adults 2 to 4 years later. This mortality must occur at some stage(s) of the life history of young loons — like migration or winter — that we have not studied well.

Average +/- standard deviation for Chick Mass Index from 1998 to 2020.

Here is the critical point. I have been suggesting that a decline in habitat quality along the migration route or on the wintering ground in Florida might be responsible for the die-off of young adults. But look at the graph above. Chick Mass Index has slid downwards steadily during the past quarter century. This means that the number of loons “fit” enough to survive to adulthood, claim territories, and rear chicks has also declined steadily. So loons are likely not dying because of environmental degradation on the migratory path or in Florida. Rather, loons themselves are of poorer quality than they were 15-20 years ago owing to limited food they received as chicks and can no longer survive the same challenges as well they used to.

Thus, the Silver Spoon Effect forces us to confront an uncomfortable reality: factors on the breeding grounds — during the chick-rearing period — are almost certainly contributing strongly to population decline. We cannot blame Florida.

But the silver spoon has a silver lining. Why? If we can improve lake conditions in Wisconsin and Minnesota so that loon parents can feed their chicks amply each July and August, we can help them raise fit chicks. And those fit chicks will grow up to become robust, successful breeders and strengthen the population.

So the answer, after all, lies in the lakes of the Upper Midwest. And my current push to discover the exact cause of water clarity decline in Minnesota and Wisconsin lakes suddenly takes on even greater importance.

$20,000 Match from a Wisconsin Foundation

If you have already donated to support our work, thank you! If have not yet done so recently, this would be a great time. Earlier this week we learned that a northern Wisconsin foundation will match every dollar raised from other sources up to $20,000. So every dollar that folks are able to donate will add $2 to our 2025 research fund.

DONATE HERE

We would dearly love to take advantage of this opportunity and field a strong research team next year. Thanks in advance, if you can help!

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This seems a dark time for loons in the Upper Midwest.

Wisconsin breeding pairs fledge 26% fewer chicks now than they did 25 years ago. Our more limited data from Minnesota indicate low breeding success there as well. (A long-term study by Minnesota DNR confirms that chick production is decreasing in the state.) The decline in breeding success across the Upper Midwest concerns me. Do enough chicks still reach adulthood so that they can sustain the population of breeders?

But, as I have discussed in previous posts, loss of chicks while under their parents’ care is less of an issue than the escalating die-off of young adult loons after they leave the breeding grounds. Survival in this later stage of the life history is down over 80%. Of 99 chicks that we banded in 1998, 1999, and 2000, we had resighted 38 (38%) as adults by 2004. In contrast, we have reobserved as adults only 9 of 155 chicks (6%) banded between 2018 and 2020.*

Of course, these young adult returnees are troublemakers. They loaf on undefended parts of large lakes or on vacant small lakes. They intrude into breeding territories. Their visits force pair members to confront them physically and steer them clear of chicks. If the pair’s hints are not sufficient to drive the youngsters off, they are attacked. Naturally, the more of these 2- to 6-year-olds there are in the study area, the greater the chance that one of them evicts a member of the pair.

But these young loons are also the future. From their ranks come replacements for breeders that die each year. So young adults — warts and all — are essential to population stability.

The huge drop in the young adult population has turned our annual spring census into a stressful experience. In early May our Wisconsin and Minnesota teams race from territory to territory to see which of our marked breeders have returned and which territories from previous years are still occupied. Each year I fear that breeding lakes will be lost because the dwindling young adult population will be unable to fill breeding vacancies.

In truth, we have lost several of our traditional territories in Wisconsin during the past few years. We did not find breeding pairs on Bridge, East Horsehead, Hildebrand, Miller, Oneida-East, Pickerel-North, Tom Doyle, Swamp, or Muskellunge (Lincoln Co.) in 2024. We seem to have lost one of our breeding pairs on Bertha Lake and another on Butterfield Lake in the Minnesota Study Area as well, although our data do not extend as far back there. Still, there has not been a wholesale loss of territorial pairs in the Upper Midwest, which one might have expected from the high mortality of young adults. So while we have far fewer young nonbreeders milling around, the decline in the territorial loon population is, as yet, small.

Thus, the loon population might be more resilient than we had feared. We have long known that the majority of young loons that return to the breeding grounds never settle on a territory. Perhaps the die-off of young adults merely reduces their number to those few that would normally claim territories anyway. It is a hopeful thought!

Meanwhile, my work continues in both states. I am connecting with water quality specialists in Wisconsin and Minnesota in hopes of learning why we are losing water clarity in July, which harms loon chicks. And I am searching feverishly — both on the breeding grounds and in Florida, where most of our birds winter — for the cause of the high mortality in young adults. These are not quixotic quests. I feel that people who love loons in the Upper Midwest will step up and help them if we can pinpoint the factors that endanger their population.

If you would like to support my efforts to conserve loons in Wisconsin and Minnesota, please consider a donation to our 2025 field effort. We squeeze all we can out of every dollar we receive.

* People sometimes ask me, ”Could these missing loons have simply gone somewhere else? Have they gone to Canada?” It is a reasonable question. Ecologists have marked and tracked movements of thousands of bird species as well as many other vertebrates. With the exception of nomadic species, though, territorial animals like loons stick to a rigid set of guidelines with respect to settlement. If it is still alive, a loon will return to the near vicinity of its natal lake as a young adult to look for a breeding spot. (This is especially true of males.)

The featured photo is by Hayden Walkush of the territorial female on Two Sisters-East. This photo is among the 1906 taken by the team this year as part of our study of whether or not loons can be distinguished using artificial intelligence.

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Almost four years ago, I wrote a blog post about the importance of Florida’s Gulf Coast as a wintering area for loons breeding in the Upper Midwest. I pointed out that 75% of loons breeding in Wisconsin and Minnesota winter along the Gulf Coast of Florida from Pensacola to Fort Myers. And I suggested that conditions in Florida were likely to have substantial impact on the loons we see on our lakes in the north.

My thoughts have returned to Florida of late. Why? Because recent findings suggest that the answer to our greatest riddle might be found there.

Followers of the blog may recall that the single most worrisome pattern related to the Upper Midwest loon decline is the mysterious disappearance of juvenile loons before they reach adulthood. In Wisconsin, the survival rate of juveniles to adulthood plummeted from above 50% to less than 20% between 1993 and 2016, as the graph from our statistical test shows.

The problem has gotten worse since 2016. Only 13 of 209 chicks (6.2%) banded in Wisconsin between 2017 and 2020 have returned as adults. That is a ghastly statistic.

What might be the cause of this massive die-off of young loons? We have good data from the breeding grounds. If juvenile mortality were high during this interval, we would have detected it. Death during migration is another possibility, of course. We do not have good data from that period. But it seems implausible that the varied array of aquatic habitats used by young loons along the migration route have suddenly become a death trap for them.

So it was with increased urgency that I turned my gaze to Florida two weeks ago with our juvenile return data in hand. My hope was to take a second, more thorough look at the likelihood of spotting loons two to four years after we marked them as chicks. I had taken a preliminary glance at this pattern 12 years ago. This time I had: 1) twice as much data, and 2) measurements of physical and biological patterns from ocean water along the Florida Gulf Coast that might help explain the decline. Among physical and biological ocean attributes that I could examine this time were water clarity, temperature, pH, salinity, and concentrations of Chlorophyll A, dissolved oxygen, nitrogen, and phosphorous.

What do the data show? After accounting for observation intensity 2-4 years after banding (which has varied during the study) and location of lake where the chick was banded (because juveniles from central lakes are spotted more often), three variables strongly predict the probability of resighting of a color-marked juvenile loon. In order of decreasing importance, they are:

  • Year — The likelihood of spotting a banded chick as an adult has decreased by an average of 8% from one year’s “crop” to the next. This is the alarming pattern that I seek to understand.
  • Body condition at banding — Chicks that are heavy for their age when banded are much more likely to be resighted as adults.
  • Chlorophyll A level in Tampa Bay in December of the first year — Chicks are much less likely to return if Chlorophyll A levels in Tampa Bay were high in December of their first year (see graph below).

Wait! Does this last finding make sense? First, it is vital to understand that Chlorophyll A is a measure of aquatic phytoplankton — the microscopic algae that can make water appear green to us. A very high concentration of Chlorophyll A can indicate an “algal bloom”, which reduces water clarity and can lead to loss of oxygen and release of toxins. Second, it is important to understand that the negative impact of Chlorophyll A on loons occurs only in December of a loon’s first winter. Return rate of juveniles is not associated with Chlorophyll A levels the month before (November) nor the month after (January). Third, we must be familiar the the migration schedule of juveniles. Juveniles reared in Wisconsin and Minnesota typically reach their Florida winter quarters in late November. Stitching all of this together, the negative impact of Chlorophyll A in December on return rate to Wisconsin suggests that many young loons perish in their very first month on the wintering grounds in Florida if algal levels are high at that time. We would expect these neophytes to be at risk during this period, because they must suddenly find new aquatic prey in wholly unfamiliar habitat. High algal levels add another layer of difficulty to foraging, likely reducing the abundance of prey as well as a loon’s ability to find them.

Of course, this is a hugely important finding. This is the first evidence — to my knowledge — where an occurrence in winter affects a demographic pattern detected on the breeding ground. The effect, moreover, is strong. And the pattern is evident despite the fact that Chlorophyll A data represent only one small part of the winter range (Tampa) that is as far as 350 miles from where some Wisconsin loons spend the winter. We can reasonably surmise that the pattern would be far stronger if we had complete data from all along Florida’s Gulf Coast and could match locations of wintering loons up with Chlorophyll A data from their exact location.

Unfortunately, this striking finding cannot explain the steep decline in juvenile survival rate over the past quarter century. Why not? First, Chlorophyll A levels have remained roughly stable in Florida — maybe even falling slightly — across the two decades or so when juvenile survival has been getting steadily worse. Second, the statistical decline in annual return rate among young adults remains strong even after we have accounted for the effect of Chlorophyll A.

In short, many of our first-year loons do appear to die in Florida, shortly after arriving there. But we are still utterly in the dark with regard to the continuing yearly decline in young adult survival. Young adult loons are future breeders — essential to the stability of the Upper Midwest loon population. It is urgent to learn what is killing them. I will keep looking.

The featured map is from Google Earth. It shows lines drawn between where a loon was banded in summer and where it was recovered or spotted during winter months. Green end points indicate Wisconsin breeders and red indicate Minnesota birds.