One of the challenges of behavioral research is to take notes that adequately describe the totality of what animals are doing. Since I am a behavioral ecologist, I devise a long list of behaviors that both appear important to the evolutionary fitness of loons and are also stereotyped or obvious enough for observers to record confidently on a datasheet. For example, when a loon bows its head so that its bill is pointing downwards instead of horizontally, we can all agree that it is exhibiting a “head bow”. When a territory owner slips quietly underwater, a nearby intruder flees across the water, and the owner resurfaces at the spot vacated by the panicked intruder, we recognize that the owner was “stalking” the intruder. We train field staff also to prioritize the recording of certain critical behaviors, like vocalizations, which reveal the motivational state of an animal and can be linked to particular stimuli occurring just beforehand (e.g. the flight of an intruding loon or eagle overhead). To aid new observers, we include a “cheat sheet”, shown below, that describes behaviors they are to look for and enter with our two-letter codes.

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Naturally, after 27 years of loon observation, we have seen or heard most of what loons can do. Indeed, we have analyzed many of these behaviors statistically to learn why loons carry them out. Yodels are a good example. By playing yodels back from loudspeakers to flying intruders, we were able to show that this call discourages many would-be intruders from landing on a lake and confronting the territorial pair. So a territorial male can employ a yodel as a means of defending his chicks from intruder attacks. Likewise, we have inferred that the mournful wail call must play a role in keeping pairs together and advertising for mates, because loons wail with great frequency: 1) when separated from their mates, and 2) when they lack a mate altogether.

But even two and a half decades of observation and statistical analysis of behavior is not enough to prepare us for everything loons do. This fact was brought home to me a few weeks back on Swamp. Following the death of the breeding female and departure of her former mate to Burrows Lake, an interesting new breeding pair had settled on Swamp. These new breeders fit the mold of many pairs we see: the female is a former breeder on tiny Prairie Lake but was evicted from there in 2015. She is at least fifteen years old and has reared six chicks to fledging. The male is a six-year old hatched on East Horsehead with no previous breeding experience. It is probably safe to say, after watching the video below, that he is still learning. To be clear, copulation in loons, when performed correctly, requires that male and female cloacas (genital openings) make firm and stable contact for several seconds so that sperm transfer can occur.

There are a few points to make here. First, though we might expect copulation, a very simple behavior pattern, to be largely instinctive, there are evidently some motor skills related to copulation (e.g. balancing on the female’s back) that benefit from learning. So males with no previous mating experience apparently fail in some early copulation attempts and must refine the behavior. Second, complex organisms show complex, non-robotic behavior patterns, especially when interacting with others of their species. Call it vertebrate bias if you like, but grasshoppers, crabs, and earthworms show a suite of behaviors that is relatively simple to catalog and describe. Loons, like squirrels and coyotes and turtles, sometimes carry out weird actions that don’t show up in the guidebook. So loon observers need to be ready to drop the two-letter behavior codes on occasion and just write down what the birds did.

Enough about science and field techniques. What I like most about this clip is that we can relate to it. If loons were humans, you could imagine the male saying, “Ok, wait….whoops….oh no…..whoa….oh gosh….umm….ok….nobody saw that, right?”

 

It was jarring two days ago to look at the database we use to track our breeding loons. During most years, the first week in June is the peak of incubation. At this time, breeding pairs that laid eggs early are well into the 28-day period that will carry them to hatching; others have lost an early clutch and replaced it. But steady, determined incubation is the rule at this time of year.

Not so this year. As the screen grab from Evelyn and Tarryn’s data entry shows, 2019 is yet another year of severe black flies. I had a sinking feeling that black flies would be a plague when I was in the study area in May.

As our recent paper shows, cool springs are killers. In years when April and May are cooler than average, black flies live longer than average. From the standpoint of a female fly, cold weather makes flight and dispersal more difficult, so a female in a cold spring is likely to delay her quest for the blood meal she needs to nourish her eggs. Not all females postpone reproductive activity, however, so cold springs reduce synchrony between female flies. The result, from a loon’s perspective, is a longer period when flies are around to harass them on nests. In contrast, warm springs cause a well-synchronized explosion of fly biting activity. During warm years, Simulium annulus blackens the skies for a few days and exacts an awful toll on incubating pairs during that brief period. Many pairs, though, are able to weather the onslaught, maintain viable eggs (no doubt aided by warm temperatures), and incubate the eggs to hatching despite the interruption.

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Elaina’s photo of the nest on Hilts Lake is typical of what we see in a cool spring. Flies are abundant, to be sure. In the photo, you can see many in the air above the nest but also scores hanging onto the arched roof on this platform. There are enough flies around the nest to keep the pair from incubating the eggs, but few enough so that this infestation does not reflect an explosion, such as would occur in a warm year.

Screen Shot 2019-06-10 at 11.07.16 AMNow that I have got you worried — sorry — you must be wondering where 2019 ranks relative to other years. What kind of productivity can we expect? I ran a quick back-of-the-envelope analysis by comparing rate of chick production in each year with the proportion of pairs sitting on nests during the first week of June. Even with the one “outlier” (2013), there is a tight correlation. That is, we can usually tell pretty well how productive a year our loons are going to have by looking at the proportion of all pairs on eggs in early June. If 2019 falls near the line, then the 0.45 proportion of sitting pairs in early June of this year predicts 0.42 chicks per territorial pair. This is not terrible — look at 2011, for some perspective — but not what we had hoped.

 

 

 

 

Although it sounds odd to say it, I often think that loons have considerably more patience and perspective than I do. Perhaps because I cover so many different territories, and because a year can go by between my visits to any one territory, my brain perceives that time is passing quickly there, and nothing is changing. This sometimes leads to frustration and overgeneralization. If I find a failed nest in June of one year and again during a May visit to the same territory the next year, I throw up my hands and conclude that the pair there is wasting their time. If on two separate visits fourteen months apart I find two intruders then three more intruders on a lake, I am apt to grumble (sotto voce): “This pair has intruder problems.” If two visits eleven months apart happen both to fall on weekends when many anglers are on the water, I become excessively concerned that the pair on the lake will soon fall prey to fishing entanglement. I suppose I am not the only person to rush to such conclusions based on fragmentary observations.

So it was almost a year ago, when I reflected upon the plight of an ABJ (adult banded as a juvenile) that had taken to stalking the Blue Lake-West territory. As you will see if you reread that post, I had grown pessimistic about the chances of that young female, “White-Green”, ever winning a breeding position on the Blue-West. White-Green, a ten year-old from Franklin Lake in Forest County, has lived for some years on Blue. She had challenged the Blue-West female for ownership at least twice that we witnessed — once in 2014, when she was only five, and once again just last year — and failed to evict the older bird on both occasions. It seemed to me that she had set her sights on gaining a breeding slot on one of the two territories on Blue and had perhaps forsaken all other possibilities. Having seen her fail twice to supplant the Blue-West female, I began to fret that White-Green would never settle.

White-Green, as it turned out, was playing the long game. She ignored the negative vibe from a grey-haired, middle-aged canoeist who visited her lake from time to time and waited. She watched for half a decade as the Blue-Southeast pair reared four chicks to fledging and the Blue-West pair raised three chicks….and waited. She witnessed the violent male battle and accompanying infanticide at Blue-Southeast in 2016, failed to take advantage of the ensuing chaos to land a breeding slot, yet waited still more. Six Mays came and went without any sign that White-Green might end her quest and finally breed. But two days ago, Elaina, Evelyn, and Tarryn found White-Green foraging near the nest platform with the Blue-West male as if doing so was the most normal thing in the world. The old Blue-West female, a 20-year-old hatched on Virgin Lake and White-Green’s former nemesis, was nowhere to be found. (We presume that, having been evicted from her position, she was cowering somewhere on this large lake, hoping to avoid White-Green.) So White-Green’s patience has finally been rewarded. Loons’ rigid, keratinized bills prevent them from ever smiling, but I have a sense that White-Green would have been doing so, if her anatomy had allowed it.

Pickiness is familiar to humans. We all invest considerable time and energy when looking for a home where we might live for a decade or more. But who knew that loons were equally choosy? Elaina and I have had a fresh reminder this past week of how finicky loons can be.

Sure, we have crunched the numbers. We know from the analysis that Mike Palmer and I ran six years ago that loons show a strong statistical preference for lakes that resemble their natal one in size and acidity. The figure above — though cropped for artistic effect — shows that both males (yellow arrows) and females (orange arrows) tend to settle on a breeding lake of similar size to their natal lake.

Knowing that loons eventually settle as breeders on lakes similar to their natal ones does not, unfortunately, tell us much about the exact means by which they choose a lake. That we must learn about by noting the sequence of lakes that a young loon visits, how long it stays on those lakes, and with whom it interacts while there. Although we have published a preliminary paper that dispels one popular idea about how loons might try to claim a first breeding territory and have long known that loons are strongly attracted to territories that are proven chick producers, we have quite a ways to go to nail the process down completely.

When we are out in our canoes, of course, we cannot see broad patterns. We simply note, for example, that a certain banded loner was at the north end of Birch Lake during the hour or so that we visited. At the end of each day, we check the database to learn the identity of any banded loon whose legs we saw clearly. Since we are tired, the discovery of a banded ABJ (“adult banded as juvenile”; i.e. a loon that we originally banded as a chick) that no one on the study has ever seen before elicits little more than a grunt of satisfaction. Then we ready ourselves for the next day in the field.

But the data accumulate. A loner that Elaina, Evelyn, and Tarryn saw yesterday at Katherine Lake, “Green over Green Stripe, Pink over Silver” matched a bird that I had encountered 24 days prior on East Horsehead Lake and that Elaina had seen on June 7th of last year on Bearskin. Three sightings do not constitute a publishable pattern, but this is a familiar observation on the project: a loon appears repeatedly on lakes of a certain size. The fact that we have seen this female only on large lakes (200 acres or more) and that she was also reared on a large lake (Two Sisters) suggests that she has a natal habitat preference for large lakes. What’s more, her apparent favoritism towards large water bodies at the tender young age of four indicates that she has already narrowed her choices, even though she will not settle to breed for two to three more years.

Our recent sightings of G/Gs,P/S — when combined with those of the 383 other young loons we have observed in the process of scouting out breeding territories — will help us piece together the strategy that young loons use to zero in on a breeding territory. If G/Gs,P/S is typical, young males and females cherry pick certain kinds of lakes to visit within their home region, skipping over many intervening lakes that do not catch their fancy. In another case, B/B,Ts/S, a male, was raised on tiny Fox Lake (15 acres), visited mainly small and medium-sized lakes when searching for a territory, and settled on Schlect Lake (25 acres). Since G/Gs,P/S and B/B,Ts/S have completely opposite ideas of what a good territory looks like, they could both inhabit the same cluster of 20-30 lakes during the two-to-three-year pre-settlement period, both search feverishly for a territory, and never meet.

We are nearing the point where we will formally analyze visitation patterns such as I have described to learn more about how loons decide on a breeding territory. Our data include sightings not only of adults but also of young juveniles in the late summer and fall after they have fledged but before their first fall migration. It seems quite possible that a rough picture of its ideal breeding lake forms very early on in the brain of a young loon.

I know: that sounds like sacrilege. How could someone who has loved and studied loons for over a quarter century make such a statement? Perhaps I can lessen the blow a bit by stating that loons are not alone. All animals, in fact, are essentially selfish. This is one of the most difficult concepts for many nature observers to understand about animal behavior.

I do not raise this topic just to be mischievous (although I suppose that is a side benefit). In the past two weeks, three people with whom I have spoken have tried to explain certain loon behaviors by first presuming that loons behave unselfishly — that their behavior somehow aims to help other loons or the entire species. So I felt it necessary to explain why such unselfish behavior should not occur.

What do I mean by saying that loons are selfish? I mean that when a loon — or a panther or a mosquito – exhibits some behavior, that behavior is, with rare exceptions, evolutionarily good for that animal. By “evolutionarily good”, I mean simply that the behavior increases the proportion of its genes in the population – its very own genes. In short, almost all animals behave so as to promote their own reproductive success, even if this comes at the cost of the breeding success of others of their species. Indeed, promoting one’s own reproductive success typically means suppressing the reproductive success of others, because others are competitors for mates, territories, food, and other resources that you need to rear your own offspring.

Why must animals behave so as to be genetically selfish, as I have stated? The easiest way to look at the problem is as follows. Consider a population of individuals of a species – like the set of all loons in Oneida County, Wisconsin. Imagine that a mutant loon appeared who began to forego its own efforts to breed and instead helped others compete for territory ownership or rear their young. While such altruism would win our hearts instantly, it would be a dismal failure in the evolutionary game. Why? Because this exemplary individual would rear no young that possessed that trait of helping others. So the next generation of loons would contain no loon that helped others in this way, and that pleasing altruistic mutation would quickly vanish from the population. This is the demoralizing truth about the evolution of behavior: selfish traits thrive; unselfish ones die out.

“Wait”, you are thinking. “Many humans are unselfish; we see altruistic acts every day; many non-human species show altruistic behavior as well.” This is a puzzle: if unselfish behavior is so harmful to an animal, why do we see so much of it in humans and other animals?

Yes, unselfish behavior — that which has a cost to the donor and provides a benefit to a recipient — is common in some animals, but only under a narrow set of conditions. First, we need to exclude all cases of unselfish behavior towards offspring. Protecting your own biological offspring from a predator or giving up food for their benefit is evolutionarily selfish, because they carry your genes. And now that we are paying attention to genes, rather than just whole individuals, we can expand our thinking and see that offspring are not the only ones that share genes with an animal. In fact, providing food or protection for any close relative might be viewed as evolutionarily selfish, and we might expect to see such behavior in many species. Why? Because, again, promoting the survival and breeding success of close relatives increases the likelihood that genes you share with them will survive and spread in the next generation. So we might expect unselfish behaviors toward close relatives – even dying to protect them in some cases – to be common as well. And they are. This is how we can understand food-sharing and joint group defense in species like honeybees, orcas, ground squirrels, Harris hawks, elephants, and termites – species that live in groups of closely-related individuals.

Unselfish behavior is not entirely dependent upon shared genes. Unrelated individuals can be unselfish towards one another as well. In fact, humans have a word for an unselfish relationship between unrelated animals: friendship. If a phenomenon is so familiar to us that we need a word for it, it must be real and important. Indeed, friendships are important and rather widespread in animals. Furthermore, they constitute an entirely new and different kind of behavior pattern, because giving an unrelated friend ten bucks, even if it helps them produce more young (!), does not help you at all through the friend’s reproduction. To see how unselfish behavior among non-relatives could evolve, we need the concept of “reciprocal altruism”, which is just a nerdy, scientific phrase that refers to friendship. The concept of reciprocal altruism holds that two individuals (of any species) might be expected to behave unselfishly towards one another (exchange unselfish acts), providing: 1) they know and remain with each other over a long period, and 2) each truly behaves unselfishly towards the other (i.e. unselfishness is a two-way street). In other words, if you give your friend food today, but you meet up again tomorrow, when you are hungry, and he gives you food, you have engaged in reciprocal altruism. This strategy is a sensible behavior pattern in cases where food or other resources are spotty but can be shared over time to the benefit of both animals. Reciprocal altruism occurs in many social species. One of the most well-documented cases is in vampire bats, in which unrelated friends reciprocally share blood meals over time such that survival is increased for both individuals.

How does this all relate to loons and their behavior? Loons, like most species of animals, are solitary breeders: they do not breed in clusters or colonies, or family groups. So there is little potential for unselfishness towards extended family or friends. The best opportunity for unselfishness in loons appears to occur when young males return to the vicinity of their natal lake at age three or four to look for a territory. Three years is a short time in this species; a returning male is likely to find one or both parents still on its natal territory when it visits there. But – and here is the kicker – we have not detected any difference between how parents’ treat their adult offspring and how they treat unrelated territorial intruders. In other words, we have no evidence that loons recognize their own young (or vice-versa) when the latter return as adults. To drive this point home in a rather unsavory way, we have had four instances in which returning sons have paired with and even produced offspring with their mother (always near their natal lake, never on it).

Thus, loons, like most other species of animals, do not look out for other loons. Behavioral ecologists like me have learned to view each animal as being on a sort of narrow-minded quest to maximize the number of its own biological offspring — regardless of the consequences of this selfish behavior for its population or species. If you can grasp this sad concept, you will be far above the average observer of nature. Perhaps, like me, you will feel somewhat compensated when you are able to tsk-tsk condescendingly the next time you hear an erroneous but well-intentioned nature video proclaim,“….and leopards never consume too much food, but instead leave enough to support others of their species.”

I was on pins and needles last week when I visited Cunard Lake. Cunard, some may recall, is the 45-acre lake where two strapping six-week-old chicks and their parents fell victim to a devastating series of events in the last few days of July 2018. On July 27th one of the chicks swallowed an angler’s bait and hook, which kept the youngster from feeding itself and led to its death within five days. On July 29th, the Cunard male found himself challenged for territorial ownership, lost the battle, and vacated the lake. In the wake of that eviction, the surviving Cunard chick too vacated the territory and blundered into nearby Hasbrook Lake, where a different pair was rearing two slightly younger chicks. The lone positive that emerged from those events was that the Hasbrook pair let the huge refugee join their family and fed it thereafter as one of their own.

Naturally, I was intensely curious to observe the aftermath of this territorial carnage. Even what little we had seen in the few weeks following the loss of the Cunard family was tantalizing. The lake was left vacant. The evicted male, the male that had evicted him, and the female from the lake all went missing. The lack of loon activity in Cunard was odd, particularly in the case of the victorious male. This male had scouted out Cunard, observed the chicks, challenged the male breeder for this proven territory, and defeated him in battle, only to desert the lake after driving away the former owner and seizing ownership.

My visit to Cunard a week ago was anticlimactic. While I had expected to see the usurping male paired with the original Cunard female — the normal aftermath in  cases of eviction — both original residents (a 15 year-old female hatched on nearby Woodcock Lake and a 13 year-old male reared on North Nokomis) were back and acting as if nothing had happened. It was a complete territorial reset. To be sure, there is a slight chance that the usurper had died during migration or over the winter. But it is far more likely, given the 94% annual survival rate of young males in their prime, that he had simply changed his mind about settling on Cunard.

We have seen this behavior before. I had always expected that evicting a territory owner and settling on its territory would occur in one fell swoop, but it is not so. On numerous occasions, nonbreeders (either male or female) have taken the great risk of challenging an owner in battle, defeated the owner, and then not settled on the territory they had invested so heavily to win. Why?

We can only speculate at this point. One peculiar behavioral pattern that might help us understand the failure of usurping loons to settle is natal habitat imprinting. Natal habitat imprinting refers to the strong tendency of loons — both male and female — to choose breeding lakes that closely resemble the lake on which they were reared. There could be a variety of benefits to settling on a lake like the one you were raised on, such as having similar prey to eat, availability of similar nesting areas, or simply being able to use one’s natal lake as a model of what sort of breeding area to look for, which might speed up the territorial search. At this point, let’s take natal imprinting as a given, since we know it occurs strongly in this species, and ask the obvious question: “Why would a loon not decide if a territory was to its liking before engaging in a dangerous battle to win it?”

As is so often the case, I can merely state a plausible hypothesis based on what I have observed of loon behavior. Territory owners, of course, are intolerant of intruders. Thus, while a loon that attempts to evict a resident from its territory is likely to have visited the territory on numerous previous occasions, the strong tendency of the breeding pair to drive out all intruders shortly after they enter prevents non-residents from learning much about the territory. As a result, once it has defeated the resident and taken ownership of its territory, a usurper might find (to it chagrin) that its hard-won territory does not resemble its natal one as closely as it had seemed. This hypothesis will be difficult to test, but not impossible. It predicts that many nonbreeders will battle for and win territories that are similar to its territory in obvious ways (like overall size) but that usurpers that find that their new lake is unlike their natal one in more subtle ways (like available prey species) might not stay.

So, we must keep working. In the meantime, enjoy my photo of a new pair that has settled on Swamp Lake. The female (on the right), evicted from Prairie Lake in 2015, seems gung-ho to settle and breed. Let’s hope the male (left) finds Swamp similar enough to his natal lake, East Horsehead, to stay.

It is my 60th birthday today. I ran 5.3 miles just to show that I still had it. Since I find running unpleasant, I listen to music in an effort to distract myself as I run. (This works poorly.) Amidst the classic hits on my playlist today (by Jim Croce, Don Henley, Talking Heads, David Bowie) was an outlier: “New Rules“, a 2017 hit by Dua Lipa. Wikipedia describes New Rules as a “tropical house, electronic dance music and electropop song with a drum and horn instrumentation”. While I do not understand most of that description, I understand enough to know that few men my age would find the song meaningful. When you consider that the song concerns a young woman’s efforts to break up with an unfortunate boyfriend, its profound significance to me becomes even more alarming.

I can explain. New Rules describes a very logical practice common to many of us: trying to interpret a vexing phenomenon and chart a course forward by looking, not at a single event, but a series of related events. The idea, of course, is that an isolated event might be misleading, whereas many events, studied together, offer a better picture of the world. And this is what scientists like me do. We resist the temptation to generalize to the world from a single event and instead study sets of related events and use statistical tests to discern patterns that may or may not align with our hypotheses. When I heard New Rules for the first time, I laughed out loud, because Dua Lipa sings “Now I’m standin’ back from it, I finally see the pattern” — referring to her boyfriend’s persistent misbehavior. This is just exactly what I have devoted my life to doing…..in a very different context.

Here is the latest puzzle in which I am trying to see the pattern: old female loons are reluctant incubators. That is, when sitting out in the open on a nest becomes unpleasant, old females are less likely to put up with the unpleasantness and continue sitting on the eggs. Instead, they tend to bail on the breeding attempt, to their great cost and that of their mate. In loons, of course, the unpleasantness derives from black flies that specialize on sucking loon blood, Simulium annulus, which are in profusion at the moment in the study area. (The photo below is from Clara Lake, where the pair is beseiged.)

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I observed the reluctance of an old female to sit on eggs on Oneida-West four days ago. The very tame male that just took over the territory this year  — a 9 year-old hatched on McCormick who settled first on Oneida-East, and then shifted to the territory on the opposite end of the lake — had a nape that was seriously chewed up. The feathers on his nape were misaligned, showing that the skin beneath them was swollen from countless bites of black flies. Disrupted nape feathers are a telltale sign that the loon has been incubating for a long period in the presence of many black flies. But the female of the pair, a veteran of 23 years breeding on Oneida Lake and mother of at least 18 fledged chicks, had a pristine nape. While her appearance was more pleasing to the eye than the male’s, it revealed her dark secret: she had been neglecting her incubation duties after laying an egg in the nest a few days before.

One pattern is clear here. Statistical analysis of known-age breeding pairs has shown a very strong tendency for pairs containing old females to abandon their eggs when black flies are severe. In contrast, old males, young males, and young females incubate clutches enthusiastically when black flies abound. Why on earth would old females have evolved to drop the ball on incubation as they do?

As a biologist, I have learned that most behavior is adaptive — it tends to increase the breeding output of the individual displaying the behavior — so I am inclined to interpret what might be called irresponsibility on the part of old females as calculated to help them in the long run. Perhaps old females have somewhat weaker immune systems than young females, so that exposing themselves to countless bites and the harmful protozoans that flies transmit might weaken them, making them vulnerable to territory eviction by a healthier female competitor. By refusing to incubate and weaken themselves, old females are costing themselves a single chance to rear young but might be protecting their ownership of the territory, which increases the young they raise down the road.

My explanation for old females’ behavior is just one possibility. It is quite likely to be incorrect. Like Dua Lipa, I will have to stand back a bit more — and collect more data on old females — to see the true pattern.

 

After the blur of our early-season census, we are left with a massive whiteboard showing all territories and their current status. Sometimes I find it pleasing to gaze at the board and enjoy what we have accomplished already this year. But this year’s whiteboard reveals a worrisome pattern: a decline in the number of occupied territories in the study area. Those territories occupied in May 2018 but on which we have not yet found a pair this year number twelve: Bullhead, Dorothy, Johnson, Mercer, Minocqua-East, Minocqua-South, Minocqua-Huber Bay, Muskellunge (Oneida County), Nokomis-North, Pier, Swamp, and Wind Pudding-East.

Before we panic at what seems an alarming number of lakes where territories have winked out, let’s consider a few other possibilities. First, we surely missed a pair or two on our original census because they were off foraging on another lake that we had not seen them visit previously. This actually happened on Spider, where I observed no pair on May 4 but where Elaina just today found last year’s pair with a nest. Second, at least a few of these now-vacant lakes will probably support pairs soon — or at least by the end of the season. Loons are notoriously slow to occupy vacant lakes and even, in some cases, to replace dead breeders. Third, it is a normal part of loon population ecology that the species ceases to breed on a few lakes each year. In order for the breeding population to be stable, of course, such losses must be offset by settlement of new pairs on territories that did not exist before. In fact, new territories — vacant in May 2018 but occupied in May 2019 — have popped up on McCormick, Buffalo, and South Blue lakes, owing to settlement by a four year-old male, a six year-old male, and a displaced thirteen year-old male with unbanded females. We will surely find a few more new territories in the coming weeks. But even those projected additions will not be sufficient to offset the apparent number of lost territories this year.

Perhaps we should look more closely at individual lakes to learn what has happened to cause territory loss. Bullhead is a mystery, as neither pair member has been seen; the same is true of Dorothy, Johnson, Mercer, Minocqua-South, Nokomis-North, and Pier. In the remaining five lost territories, though, we can see that male has simply not returned. In each of the five, the female has come back from migration, settled on the territory, and has found no male with which to breed. Broadly, the pattern is not surprising; it is what we expect in an adult breeding population that is female-biased. As I have noted many times in this blog, males senesce and die much earlier than females, and this causes a persistent dearth of the former and a surplus of the latter among adults wishing to breed. Could we be seeing the leading edge of some die-off among male loons that will push the population into decline? It is possible but not likely.

Let’s try to match up this year’s apparent decline in territories with likely causes. While scientists project the long-term withdrawal of loons from northern Wisconsin owing to climate change, and loons each year face slightly greater human impacts from angling, boating, and shoreline development, negative impacts of these factors should occur gradually, not in one or two years. So the net loss of six or seven territories we have seen this spring (after accounting for the gain of three territories and a few pairs missed) seems too great to be a harbinger of a larger population decline. Thus, I will tentatively conclude that this year’s losses are a blip — a short-term downward bounce in number of territories caused by chance and/or a temporary downward shift in breeding success.

Could the decline come back to loons’ nemesis, the black fly Simulium annulus? Possibly. Looking back across years, in fact, we see the dreadful breeding year of 2014, caused largely by the prolonged explosion of black flies in that year. Male chicks that would normally have hatched in 2014 would be at their crucial settlement age of five right now. So we might speculate that the “missing” five year-old males — males that would have slid into many of the territory openings for male breeders that are evident this year — are the cause of this year’s decline in active territories.

If my speculation is correct, we should expect a sharp increase in the rate of territory settlement (i.e. a net increase in territories within the study area) in 2020 and 2021, because those years fall five years after the productive breeding years of 2015 and 2016. We shall see. In the meantime, perhaps I can dispel some of the negative feeling caused by all this talk of territory decline by showing you this year’s nest on Hanson Lake. Though she took a short incubation break two days ago, which allowed me to snap this photo, the female soon jumped back on the eggs. She seems determined to do her part to help reverse the current downward trend.

I have been out on the lakes for the past fifteen days. This time of year, we race around to all of our study lakes from the previous year – and a few more where we suspect new pairs might have settled – and see who is on territory. We do not dawdle; our task is to identify the pair present on each territory and move on to the next. It is an exciting but frantic annual ritual. While we usually observe the breeding pair on each territory for an hour, a minute will suffice during scouting, because we are merely confirming the identity of breeders, then moving to the next lake. Therefore, on a really good day – if the loons are easy to find and show us their bands – a scout might hit ten lakes.

I had the kind of scouting visit we dream of on Lake Seventeen on Sunday. Seventeen has beautiful clear water, but it is large (175 acres) and has multiple bays and convolutions. One can be certain that a visit there will require putting in the canoe and searching for twenty minutes or more for the birds. Three days ago I stopped by a home at the northern tip that is our access point, glanced at the lake as I habitually do, and was delighted to see the pair foraging thirty meters offshore. I grabbed my binoculars and ran to the water’s edge. Five minutes later I confirmed that the male was “Yellow/Silver, Green/Copper” and the female “Silver/Red, Pink/Red”. The loons were so close to my position that I even observed several small bluegill scatter and flee to within inches of shore as the female pursued them. For a moment I wondered what life must be like for a small fish that ventures occasionally into open water, where predators lurk. But my reflection was cut short; I had six more lakes to hit that day.

Few scouting visits go as my recent one to Seventeen did. Yesterday, in fact, I had one of those days when I think that loons might have gone extinct suddenly. The pair on Tomahawk-Little Carr territory was cooperative: I got their bands quickly and saw them building a nest in their usual spot. But that was the end of my good fortune. I was skunked on Bullhead Lake, where the pair was missing (for the third visit this spring), and the usual nesting location showed no signs of usage. Minocqua-North, an area where the Bullhead pair has foraged in previous years, was also vacant, though I found two patches with marshy hummocks that would make excellent nesting spots. In short, the banded male and female of Bullhead, consistent breeders and chick-producers since 2010, are at large. The same is true for Minocqua-South, where a banded pair first nested on an island in 2018. Johnson Lake, where the banded male was caught on a fishing line­­­­ last May, was empty as well. My next lake, Mercer, is one we dread, because both pair members are extremely skittish. A typical datasheet from Mercer following an hour-long visit might list the leg band colors of the male and female, respectively, as “Red or Orange?,light band?” and “banded?”. It is that bad. After an hour and 53 minutes of exhaustive searching yesterday, though, I would have been thrilled just to see a loon. As on the three previous lakes, I did not find the pair.

2019-05-12 06.14.19

Yesterday’s hours of fruitless scouting ended the first round lake visits with a whimper. All other days have gone far better, however. Linda’s great work at the southern boundary and my observations in the central and northern parts of the study area have clarified the picture of who is back and who is not. Though I was stung by the disappearance of many banded and well-established pairs — or possibly my failure to find them – I also can look back and smile at the return of the venerable female from Upper Kaubashine. Banded first with her chicks in Vilas County in 1993, she has been a most successful and itinerant breeder, having produced chicks with at least four different mates on four territories. She is at least 31 years old and probably older. So let’s lift a glass to this resilient bird (on left in photo with her larger mate). With luck, she will dodge the blackflies, raccoons, eagles, and fishing lures, and add two more offspring to her lifelong tally.