Juvenile loons are in a race against time. While their parents seem to relax following the breeding season — wandering from lake to lake as if on a goodwill tour — juveniles, like the three-month-old in Linda Grenzer’s photo, face a ticking clock. After hatching in June or July, juvies must reach near-adult size by ten weeks of age, practice takeoffs and landings, and become strong enough to make flights of hundreds of miles on their southward migration in early November.

They are racing the ice. Temperatures cool in September, become unpleasantly chilly in October, and truly plummet in November — and lake temperatures follow suit. Ice-up can occur anytime between mid-November and mid-December in northern Wisconsin, and ice-up is the end of the line for juveniles. Opportunistic bald eagles await juveniles that are not prepared to migrate and become trapped in the ice. Apparently sensing the desperate task that will confront their offspring in the fall, parents stuff them with fish for eight long weeks in July and August. Chicks grow explosively during mid-summer. But they face their most challenging task in autumn, when parental support wanes and they must learn to feed themselves, improve their body condition, and prepare for their southward journey.

In general, scientists have paid little attention to the juvenile period in birds. Our neglect is natural enough. The breeding season is chock full of interesting behavioral and ecological events: pairing of mates, defense of breeding territories, selection of nest sites, and relentless territorial intrusions by nonbreeding adults seeking to settle. Perhaps ecologists can be forgiven for focusing their attention on breeding behavior and trusting that juveniles will take care of themselves.

But we wondered. If young adults settle on breeding lakes that closely resemble their natal lakes, might juveniles — which must fight for their lives just to become adults — also exhibit clear preferences for certain kinds of lakes over others? Constrained by flightlessness to forage only within the lake where they hatched, we might expect juveniles to become highly specialized to hunt and consume the species of prey found on the natal lake. So once they become capable of flight, we might expect them to visit and forage on other lakes very similar to their natal one. That is, juveniles reared on a diet of bluegill sunfish and used to hunting that species should spend most of the pre-migratory period visiting lakes full of bluegill that they can catch and consume efficiently. And juveniles accustomed to eating snails and leeches should find lakes full of those invertebrates on which they can feast.

Our interest in lake visitation patterns of juveniles during fall inspired us to plot the local movements of youngsters between lakes in the fall of 2012, 2013, and 2014. Kristin, Gabby, and Nathan used their band-spotting skills to locate juvies in September and October of these years. They found close to 200 cases where a juvenile we had marked had flown to forage on a lake other than its own. Using these data, Brian, who joined us this summer, asked, “Do juveniles forage on lakes at random, or do they prefer to forage on lakes like the one that hatched them?”. As the figure below shows, the mean difference in pH between a juvenile’s natal lake and the lake where we spotted it foraging (red vertical line) was far less than the distribution of differences we would have expected, if juvies had foraged randomly (grey bell-shaped curve).

Z_pH_Randomization

Although Brian has a few statistical checks to complete, the pattern seems clear. Juveniles exhibit strong preference for lakes that resemble their natal one in two respects: 1) pH and 2) water clarity (data not shown). Brian’s analysis is ongoing, and he is trying to learn how closely these chemical and physical attributes predict the food available to loons in a lake. But we are betting that the stark preference of three-month-old juveniles for lakes that remind them of home occurs for a simple reason. Juvies try to spend their time hunting prey in familiar conditions to build themselves up for their most dangerous first southward journey.

In the dream, I am swimming in a tiny lake – a lake so small that two residents on opposite ends of it could converse without raised voices. The lake is completely encircled by cottages. Docks overhang almost every inch of shoreline, looming menacingly over the water and rendering the lake smaller still. The lake, in fact, looks more like a pond hastily dredged by developers for a suburban apartment complex than a pristine aquatic habitat where loons might live. But in the dream a pair of loons swims about the lake with me, investigating future nest sites after having lost their first nest of the year to a predator.

I awoke yesterday with this dystopian scene vividly in mind. The dream reflects, I suppose, my growing unease over the future of loons along the southern fringe of the species’ breeding range. My concern is fueled by an ongoing analysis of the decline in chick survival since 1993.

That analysis has progressed since I first mentioned it. The investigation started as just a hunch — an uneasy feeling that singleton broods were becoming more common. Now, having looked at the data formally in a controlled analysis, I have brought the decrease in brood size more sharply into focus and verified that it is real. There has been a systematic, highly non-random decline in brood size over the past quarter century in Oneida County.

My worst fear took shape in the dream. I fear that growing recreational pressure, shoreline development, and perhaps environmental degradation have conspired to rob breeding pairs of a chick here, a chick there — to the point where the population might be affected. My recent analysis provided a hint about the cause: the decline is far greater on large lakes than small ones. Large lakes, of course, are those most affected by increased human recreation.

It is early still. I have much investigation yet to do, especially testing specific measures of human activity (like fishing or boating licenses issued in Oneida County) to see if they are tightly correlated with chick losses. But for a worrywart – and a vivid dreamer – these are unsettling times.

Last year I wrote a blog post in which I concluded that late-hatching chicks returned at a rate no different from early-hatching chicks. I found the result surprising, as one would expect early hatchlings to have a head start in learning to feed themselves, honing their flight skills, and preparing for their first migratory journey. The photo and story I got from Linda Grenzer a few days ago has forced me to wonder if I need to collect more data on this question.

The breeding pair on Squaw Lake had an eventful year in 2018. Delayed, like all other pairs, by the late thaw, they initially nested along the shoreline near the boat landing. After a predator snatched both eggs off of the nest, they nested again not far away. This time they were more fortunate; the eggs hatched, but not until about July 22. When we captured the family on August 3rd, we found the chicks almost comically small — two little puffballs that did not approach the size of the many other juveniles we had encountered. Chicks are cute in their first few weeks, and we enjoyed observing them and handling them cautiously while giving the female a new set of bands.

Our delight at seeing the adorable chicks was tempered by the fear that chicks hatched so late would not mature in time to complete the southward migration. The fear is justified; parents must balance the energetic demands of their demanding offspring against their own need to maintain good body condition and prep for their autumn journey. Inevitably, adult loons spend progressively less time on their home lake in September as they forage intensively, molt into drab winter plumage, build up fat levels, and, in late October or early November, head south. This goes for parents and non-parents alike.

So it was not surprising to get a report from Linda that the Squaw adults had left their breeding lake, leaving their late-hatched chicks to fend for themselves. What was alarming was that one chick had chased someone’s jig, managed to hook itself above the base of the bill, and was no longer diving or foraging normally. Further evidence of its desperate condition was that it was not difficult to capture and weighed a mere 1750 grams — roughly 1 kg less than it should have at 9 weeks. Following an X-ray at Raptor Education Group, Inc. in Antigo, the chick was found to have swallowed a second hook from a separate encounter with an angler.

Since we have long since ceased our routine visits to study lakes, we can only speculate about the series of events that put the chick in this bind. Marge Gibson of REGI suspects that, without parents to help it satisfy its foraging needs, the chick was struggling to feed itself. In its desperation, the chick began to attack fishing lures until the hook in its cheek and weakness conspired to incapacitate it.

If Marge is right, and late-hatched chicks are sometimes left with too little feeding capacity to maintain themselves, then this pattern should show up in our data. Specifically, we should see fewer very-late-hatched chicks return as adults to the study area. This plausible scenario will fuel another round of data analysis…when I find time!

To end on a positive note, the angling victim is bouncing back at REGI and feeding voraciously. If you do not believe me, look at this video from the REGI website.

https://www.facebook.com/RaptorEducationGroupInc/videos/470615703434171/

If it continues to thrive, the REGI folks will face another challenge: what to do with a healthy juvenile, but one whose stay in captivity and recovery made flight practice impossible.

 

To those of us accustomed to looking at loons during the summer, the sight of an adult caring for three chicks — as in Laura Unfried’s photos from two days ago — is peculiar. Loons, of course, almost always lay only two eggs. If they are lucky, two chicks hatch. It is by no means certain that those two chicks will survive to fledging age. In fact, 47 of 61 breeding pairs we study have one chick, not two. So the spectacle of two adults caring assiduously for three young was startling.

Close inspection of Laura’s photo from Hasbrook Lake reveals another peculiarity: the central chick is much larger — perhaps 10 days older — than the other two chicks. (Note that the left-hand chick is entirely downy with a small bill, whereas the center one has the anterior part of its head coming into adult feather and has a bill nearly as thick as the parent’s.) The obvious size disparity told Eileen Lonsdorf, who reported the third chick three days ago, that her nicely balanced family of two parents and two chicks had been joined by an interloper.

How could a huge, healthy chick somehow get separated from its biological parents and join another family? Territorial behavior among loons guarantees that each breeding pair will nest and rear its young far from other pairs. The likelihood of a chick straying from its own family to join another — fortuitously or by design —

SONY DSC

seems remote.

One lesson that you learn if you do something for a long time is that rare events do occur. Chicks do very occasionally leave their parents and territory to join other families. We have noted two causes for such chick dispersal. First, starving chicks, especially beta chicks on small food-limited lakes that are being physically beaten by their alpha siblings, sometimes attempt to escape the abuse and find an alternate loon family nearby that will feed and protect them. Second, chicks that lose one or both parents to territorial eviction are forced to flee their natal territory and seek parental care elsewhere, if the adult that evicted a parent physically attacks them.

Solitary journeys by displaced chicks seeking new homes are desperate enterprises. One reason for this is that many lakes with loon chicks simply have no neighboring pairs with their own chicks that might be joined. Even if a displaced chick is fortunate enough to find a nearby pair with chicks, they are likely to be much older or younger than itself. If so, it is unlikely to be accepted by the new family. I vividly recall a case in 1999, when an abused beta chick undertook an astounding 1/2-mile trip across woods and roads from Benedict to Bug Lake in Vilas County, only to land with a foster sibling three times its size that beat it mercilessly until it perished.

Since the monster chick that joined the Hasbrook pair is a robust, well-fed individual, we could rule out that it fled to Hasbrook because of sibling abuse or lack of food. So we were left to conclude tentatively that a nearby territorial eviction forced this young loon to relocate. We pulled out a map to assess the possibilities.

Screen Shot 2018-08-03 at 6.04.18 PM

Immediately, we pinpointed Cunard Lake, which is separated from Hasbrook by a quarter mile of woods and bog, as the likely source of the wandering chick. Cunard, a regular study lake of ours, had two large, healthy, 5-week-old chicks at our last visit on July 25th. Yesterday, however, I found the lake empty of loons, except a single floater adult. The steward of the campground reported that loons had been chasing each other repeatedly across the water on July 30th and 31st, which indicated a protracted territorial battle. The absence of the territorial pair suggested strongly that the breeding male had lost the battle to a usurper and either died or been forced to abandon his territory and chicks. This tragic event, in turn, would have scattered the rest of the family and subjected the chicks to attacks by the new male owner.

Last night we captured the peculiar but close-knit family of two adults and three chicks on Hasbrook. It will require genetic analysis to be certain that the huge new chick on Hasbrook is a refugee from Cunard and the offspring of the displaced Cunard pair, as we surmise. But we have strong reason to believe that he is a most fortunate survivor of a desperate overland journey.

Few loons have endured the frustrations that the current Mildred female (“Taupe Stripe”) has. Initially captured and banded on Soo Lake in 2004, she reared two healthy chicks with her mate in that year. But each year since has yielded no offspring for this bird, despite consistent effort.

Taupe Stripe’s struggles started when she was evicted from Soo by a stronger female in 2006. Thus began an itinerant lifestyle: temporary settlement as a loner on Goodyear Lake and frequent intrusion into other lakes in the area, probing for an opening. In 2010, she finally secured and defended a breeding position on Maud Lake. Like other small, shallow lakes, though, Maud suffers from a limited prey base. Efforts by the loon pair there in the three years before her arrival were excruciating — hatched eggs followed by starvation of chicks in the 2nd week of life, the first week, and then the fourth week. Taupe Stripe and her two mates fared no better, failing to produce young in 2010, 2011, 2012, and 2013. She fell off our radar in late 2013 and 2014, but resurfaced in 2015 and 2016 — again, as a floater.

When day to day survival is a challenge, as it is for loons, you focus on the present. Taupe Stripe ultimately settled on Mildred Lake in early 2017. Unlike Maud, Mildred is a large, clear lake with a strong record of fledging chicks that hatch. Although she and her unbanded mate lost a small chick on Mildred last year, they have turned things around. Last week we caught Taupe Stripe, her mate (now banded), and their strapping six-week-old chick. Things were still looking good for the family upon my visit there today. And thirteen years of pointless wandering, frustration, and disappointment are forgotten.

For the past several years, I have begun to turn my attention to the effect of lake size on breeding success of common loons. Clearly loons on large lakes produce more and healthier chicks than those on small lakes. We showed that on our paper from six years ago. This raises the question of why loons ever attempt to breed on small lakes. They are doomed to failure — or at least to greatly reduced likelihood of success. The water is muddied further by the fact that loons reared on small lakes prefer to breed on small lakes themselves. That’s right: chicks fortunate enough to avoid starvation on small, food-limited lakes replay the whole scenario as adults, subjecting their young to the same travail they themselves faced.

The puzzle of loons breeding on small lakes was thrown into start relief again yesterday, when I visited the Wind Pudding-West territory on a scouting trip for nocturnal capture. After not finding the chick and parents in the shallow bay on the lake’s western side, where we had seen them on previous visits, I headed towards the channel that connects that bay with the main lake. I was crestfallen when I reached the channel, as it was choked with lily pads and grasses to the point where it was difficult for me to find a passage through — even in a canoe. This discovery led me to doubt whether the pair might lead their chick through the channel and into the main lake as a means of finding more food for it. I began to fear that — walled off from an abundant source of food — the chick had probably starved to death on the shallow western bay since our last visit.

I had underestimated the determination of the pair to provide for their chick. As I paddled to the end of the navigable portion of the channel, I heard a chick’s desperate cries to its parents. I spotted the chick about half way across the marshy isthmus that now separates the shallow western bay from the main lake. The isthmus is no more than 20 meters wide perhaps, but it is densely overgrown with marsh grass to the point where the chick — equipped only with legs at the very posterior of its body — was forced to lunge awkwardly forward in order to make headway towards the main lake. To make matters worse, the chick had no clear idea of where it was going. I caught the chick’s initial confusion on video, as it sits within the marsh grass, uncertain how to extricate itself.

The second installment shows the chick after it has blundered around in the grass for a time but finally gotten a sense of where its parent wants it to go. The chick stops to give a distress call, then hears its parent call to it, which seems to give the chick the strength to complete its journey. (Apologies for the nervous narration and grainy video!)

The fact that the parents can entice this year’s chick to cross the isthmus and take advantage of food in both the western bay and main lake means that they are better off than they were here in 2016, when a chick wasted away and finally died of starvation. However, we caught the chick and female in the video last night. They are both severely underweight. The female, in fact, has the lowest mass we have ever measured for an adult loon. So even if the pair can find enough food to fledge the chick, chick-rearing seems to have taken a toll on the parents. Add yet one more item to the growing list of reasons to avoid breeding on small lakes with limited food.

Since snow and ice lingered far too long this spring, loons were late to nest in northern Wisconsin. The lateness of the season has also reduced opportunities to renest after early nest failures. There was simply limited time for pairs to weather four weeks of incubation and still rear the chicks to a point where they could learn to fend for themselves and make their way to Florida. Add to the narrow window this year the mishaps that cost us young chicks on several territories….and I was beginning to sweat.

But my fears of another off-year for nesting success in the Upper Midwest loon population have not been realized. A relatively short period of black fly abundance has helped immensely. As our recent paper showed, abandonments from black fly harassment are a good predictor of nesting success; that pattern has continued in 2018. So it seems likely that this year will break our four-year breeding slump.

Here are the numbers. As of July 4th, we had an estimated 48 breeding pairs in our study area with a chick or chicks. Eighteen (give or take a few) were still on nests, of which over half will produce chicks also. That leaves us with roughly 60 loon pairs with chicks. A handful of the 60 pairs will lose their chicks before 8 weeks; in addition, though, we will make roving visits to non-study lakes within and just outside the study area and find about 6-8 more pairs with chicks. When the dust has settled, we should end up with a number of pairs with chicks that is very close to the 65 successful breeding pairs we were able to band in 2013. That fact is worthy of note, because 2013 was both a year in which our procedures and lake coverage were similar to this year, and the last solid year of breeding. So we can all breathe a great sigh of relief — and enjoy Linda’s cool photo of the freshly-hatched chick on Muskellunge Lake and the female, with moist eggshell fragments still adhering to her breast.

As of today, 32 of our territorial pairs have hatched chicks. We are on pace with last year, despite the three-week delay in nesting resulting from the cold winter. I am encouraged; 2018 looks to be at least an average year for chick production.

My optimism about the breeding season has been tempered of late, as we have gotten fresh evidence of the frailty of newly-hatched chicks. In the past two weeks, four pairs with tiny chicks have lost them — a higher than average rate of loss. Linda first reported that the chick on her lake suddenly disappeared; her observations suggest that a snapping turtle might be the culprit. Yesterday, the chick on Crystal Lake (Lincoln County) fell victim to the attack of an intruding loon, as reported by a lake resident. And two northerly pairs — on Blue-Southeast and Carrol — also completed four weeks of incubation only to lose their chicks in the first few days after hatching. The causes of chick loss are unknown in these two cases.

Loss of chicks in the first two weeks of life is not terribly surprising. Young chicks must confront a great many challenges, including simply keeping themselves warm and avoiding physical injury as they learn to swim and move about. But the greatest hazards to hatchlings, we have learned, are strictly biological. Being tiny, having limited mobility, and with only a vague sense of the dangers posed by much larger organisms in their habitat, young chicks can be attacked and killed by a wide variety of animals — intruding loons, snapping turtles, muskies, and eagles, to name a few. In contrast, adult loons are wary, agile, and large enough that the list of potential attackers is short. Adults have simply outgrown much of the danger from other living things in their environment.

As discouraging as it is, I am convinced that this recent spate of chick deaths is a statistical blip. There has been no sudden change in the loons’ habitat, or explosion in the population of any predator, that could signal the beginning of a worrisome trend. Rather, this is just an unfortunate negative swing that will be washed out by later swings, negative and positive, and ultimately forgotten. Perhaps we can hurry the process along by focusing on Linda’s recent photo of the female (“Honey”) and chick on Muskellunge Lake.

In Linda‘s last round of photos from Bear Lake, you can see the numbers clearly. At the narrow end of the metal band, a fuzzy, curling “6” followed by a clear, swooping “2”. Those two digits — either one of them, actually — identify the Mystery Female of Bear Lake as the chick we banded on July 18, 2005 on North Nokomis Lake. This photo culminates several days during which Linda patiently stalked the female with her camera lens until the bird finally pulled her metal band out of water in an orientation that permitted Linda to photograph the two digits we needed to see from the nine-digit number code.

The story of the Mystery Female concerns more than just solid detective work and crisp photography; it relates to the crucial decisions that a loon must make while attempting to settle on the best possible breeding lake and rear as many offspring as possible. The Mystery Female, Orange over Mint-burgundy — OMb for short — faced such a decision. OMb returned to the study area as a 4-year-old in 2009 and began hunting for a place to breed. She settled on Upper Kaubashine (at the end of the long arrow below) in 2012 and lost clutches of eggs to predators there in both 2012 and 2013. OMb then

N Nokomis to Bear w UK also

faced a stark choice — remain on a poor territory attempting to breed or abandon Upper K and try to move to a more promising locale.

Shifting from a poor territory to a good one might seem like an easy call to make, but female loons must cope with a shortage of potential mates owing to early senescence and frequent fatal fighting in males. Every year we see many loner females, some of which live on good breeding lakes, waiting for a mate. So it is an open question whether a female should desert a mate and breeding territory — even a poor one — to try and move to a better location. You see, in trying to secure a new territory, a female must temporarily leave her current one, risking its loss to another female on the prowl.

OMb decided to abandon Upper Kaubashine in 2013, establishing herself as the new breeding female on Bear Lake (shorter red arrow), whose female had died. This appeared to be a wise move; Bear had yielded chicks in 9 of the previous 13 seasons, while Upper K had not fledged a chick in 35 years.

Chance plays a big role breeding success of loons, as in all animals. In a curious twist of fortune, Upper Kaubashine stunned lake residents by hatching two chicks from a terribly exposed nest site. Since Bear Lake only produced a single chick this year, OMb’s choice of Bear over Upper K looks like a poor one, as of now. But chick production in these two lakes will probably return to form. If so, and if OMb can hold onto her new territory, her decision to leave a perennial failure for a proven chick-producer will have been a good one.