It is only a glimmer — the kind of glimmer one often gets when eyeballing new data. But the implications of this small discovery are enticing.

You see, I have been looking at our data on tameness, Since 2014, our team (mainly Kristin, Seth, Mina, and Nelson) has measured tameness of loons by creeping up to birds resting on the surface. We do this by first measuring our distance to the loon with a rangefinder and then paddling slowly in its direction, taking distance readings every few strokes. The final distance reading — just before the loon dives to avoid us — is our measure of tameness. Determined in this way, tameness varies from well above 50 meters to less than 2 meters. (In fact, some of our marked birds, like the male in Linda Grenzer’s photo above, find our approach so unremarkable that they simply veer slowly out of our path, instead of diving.)

We can examine the origins of tameness in far greater depth than most other studies, because we have tameness readings on many sets of close relatives in the study area. In fact, owing to the duration of our study, the limited natal dispersal of many individuals (especially males), and our efforts to find adults that we banded as chicks, we now have tameness measured for 60 sets of relatives. These include Linda’s male (“Clune”) and his son, who breeds on tiny Virgin Lake; the notoriously skittish male on Oneida-East and his full brother on Hughitt; and the Bear female and her full brothers on Cunard and Gilmore (all three banded 13-15 years ago on North Nokomis Lake).

As the figure below shows, we have noted a strongly and statistically significant relationship in tameness between parents and offspring. This pattern implies that either: 1) offspring inherit their tameness from parents, or 2) parents teach their offspring to be tame or skittish during the chick-rearing phase (or both). Either way, similarity in tameness between adults and their young means that despite being measured on different lakes, many years apart, and at very different ages, tameness is stable within individuals and is largely fixed early in life. A loon’s degree of tameness is, in effect, part of its personality.

Screen Shot 2019-02-17 at 10.00.46 AM

Parent/offspring similarity in tameness is more than a hollow novelty. Since tame parents produce tame young (either via genetics or rearing environment), those young should respond to the habitat in much the same way as their parents. I am in the process of writing a proposal to the National Science Foundation to study, among other topics, the possible impact of loon tameness on habitat selection. Specifically, I wish to test the hypothesis that tame loons might be suited to lakes with lots of human recreational activity (generally large lakes) and skittish loons to lakes with limited human activity (generally small ones). If this logical hypothesis holds up, then pity skittish individuals. Since human activity is increasing, and even many small lakes now see frequent human usage, skittish loons appear to have a small — and shrinking — set of lakes on which they can breed. Moreover, the reduced chick production of small lakes might also doom skittish loons to poor breeding success, so that fewer skittish individuals are produced each year.

The long-term consequences of parents passing skittishness to their young and fewer offspring produced by skittish loons are easy to guess. Tame loons will produce a large proportion of all offspring in the northern Wisconsin population, and tameness should increase in frequency in coming decades to the point where skittish loons are hard to find at all. This vast behavioral shift might go unnoticed by most observers, since there will still be loons on the lakes. But to an ecologist, it is exciting to think that we might be on the brink of learning the precise mechanism by which a population of an important animal can become tame.

 

 

I have touched upon this theme before. A peril of longitudinal investigation is that one decides, after a period of time, that one understands the system. So it has been with the Loon Project.

For many years I have thought I had a good handle on territorial behavior. Indeed many aspects of the loon territorial system have become clear during the course of my work and are not in doubt. Both sexes usually fight to claim their territories and face the constant threat of eviction. Males, which establish strong ties to a territory through controlling nest placement and learning where the best nest sites are, fight harder than females, and sometimes die during territorial battles. Early senescence among males sets the stage for them to become very territorial and aggressive as they reach their declining years (their mid-teens in many cases), which seems a means to help them eke out another year or two on a familiar territory.

But I was way off in my understanding of the role of lake size and body size in territorial behavior. I have always thought of breeding territories on large lakes as much sought-after, because large lakes have ample food for rearing chicks. (Small lakes, you might recall, run low on food for chicks, resulting in lower fledging success.) If large lakes produce more young, I reasoned, large-lake territories must be highly desirable. Competition must be fierce, then, for these territories. A recent analysis of territorial tenure — how long a male or female can hold onto their territory before getting evicted from it — has forced me to rethink the effect of lake size on territorial competition. The figure below is a plot of territorial tenure versus body mass for males on lakes smaller than 20 hectares (50 acres) in size (like Langley, whose current pair is pictured). As you can see, small males — especially those below 4600 grams — have very short stays on small lakes, in most cases, while large males — notably those heavier than 5000 grams — often enjoy very long territorial tenure. This pattern suggests that, contrary to my expectation, territorial competition is fiercer on small lakes than large.

impact of lk size, male body size, on terr tenure

Let’s look at the same pattern on medium-sized lakes (20 to 80 hectares; or 50 to about 200 acres). You can see that the overall pattern is still evident, although it is weaker here, because a number of very large males (5400 to 5800 grams) have anomalously short tenure.

i2 mpact of lk size, male body size, on terr tenure

Finally, let’s inspect the data only for males on lakes larger than 80 hectares (200 acres). In contrast to my earlier hypothesis, large males are not holding their territories any longer on large lakes than are small males, as you can see from the plot below. Males of all sizes may enjoy long tenure on large lakes.

3impact of lk size, male body size, on terr tenure

How on Earth do small males hold their territories much longer on large lakes — which  seem much in demand, get more intrusions, and appear difficult to defend — than on small lakes, which get fewer intrusions and should be more easily held? I don’t know exactly how males hide in plain sight on large lakes, but it might have to do with the difficulty that territorial intruders have in simply finding a nesting pair and identifying nesting habitat on large lakes. Consider the Lake Tomahawk-Little Carr pair. This pair nests in a marsh at a well-hidden location. When one bird is incubating, its mate is usually far off in the wide open portion of Lake Tomahawk, which is many kilometers long and has an area of 1400 hectares (about 3500 acres). A male intruder might well find and socialize with the off-nest pair member on on the big water, but it would have no way of knowing that the mate of this loner was on a nest hidden far away in a marsh. Similarly, when the eggs hatch, the pair quickly leads the chicks to the main bay of the lake, far from the critical nesting area. Pairs with chicks provide an enticing cue to young males seeking territories, because the presence of chicks tells of the availability of nesting habitat. But a male intruder that encounters the Tomahawk-Little Carr pair and their chicks on the main bay of the lake would face the needle in the haystack problem in locating the precious nesting area that yielded the chicks. A dangerous battle might win the territory, but the knowledge of how to use the territory (that is, where to place the nest) would vanish with the old male’s departure. Hence, large lakes appear to be less valuable to males.

A male intruder bent on taking a territory likely to yield chicks in the future would be better-served by evicting a chick-rearing male on a small lake. Such an intruder would have a much smaller set of nesting areas to inspect and would likely find and use the nesting area that produced the chicks. Thus, we might expect stronger competition among males for small, easy-to-learn territories — a pattern that dovetails with the longer tenure that large, competitive males enjoy on small lakes, compared with small, easily-evicted males.

What about females, you might ask? Do large females on small lakes, like large males, have an advantage in holding their territories when compared with large females on large lakes? If my hypothesis is correct, and the value of a territory depends upon knowledge of safe nesting areas, then large female size should not be especially beneficial on small lakes. Indeed, any impact of female body mass on territorial tenure should be equal across all lake sizes. Why? Because females do not control nest placement in this species. An intruding female that evicts a breeding female with chicks and pairs with the breeding male would have access to that male’s knowledge of nesting sites on a lake of any size. As predicted, large size is no more beneficial to small-lake females than large-lake females. (Indeed, size has an overall weaker effect on competitive ability in females.)

So my post hoc hypothesis for the fierce territorial competition on small lakes holds for the time being. My explanation is not the only one consistent with these data, by the way, and there remain many further tests to run. For example, we might expect competition not to depend strictly upon lake size per se, but upon the obviousness of nesting habitat. In other words, an intruding male should fight hard for a large-lake territory if the territory contains islands or other obvious safe nesting habitat, but not if there is no clear nesting habitat in the vicinity of a pair with chicks. We might even expect that breeding pairs on large lakes would purposely move their chicks as far as possible from their nesting areas, in order to avoid betraying their whereabouts and getting evicted. Clearly a refined, more robust test of the hypothesis is in my future.

Finally, a plea. I am about two-thirds done with a new long-term NSF proposal, which might fund my work for 5-10 more years. Even if I get the proposal funded, though, the funds will not be available for 6-8 months. So we are facing a 2019 season with very minimal funding — fumes from the end of my current NSF grant. To have a chance for future funding, we must continue to cover the study population. Please let me know if anyone can help us out this year with 3 weeks of lodging (or some portion of that) early in the season (late April-early May) and/or 3 weeks (or part of that) in July-August, when we must capture and mark pairs with chicks. We might be able to pay a very modest rent, if my remaining funds are not gobbled up by travel. I am embarrassed to ask this, but I am desperate. I just do not know where we could possibly afford to stay this year. Thanks for any help!

 

 

Behavioral ecologists are human. Although we try hard to view biological events critically – to look for confounded factors, biased samples, untested assumptions – we miss a lot. So it is when we look at the nesting behavior of birds.

Ecologists around the world have made a simple, elegant discovery about how birds respond to nest failure. Once they have settled on a breeding territory and reared young successfully once, breeding birds get conservative. They reuse the same nesting site again and again. On the other hand, if they try to nest in one location and the nest fails, they shift to a new location. We call this simple strategy the “win-stay, lose switch” rule.

Let’s think a bit more about the win-stay, lose-switch (”WSLS”) nesting rule. What is it about a nest’s location that links it so critically to success or failure? The main answer is predation. Most predators are long-lived mammals (raccoons, squirrels, foxes), reptiles (mainly snakes), or birds (crows, jays, hawks, or gulls) that travel within fixed small ranges looking for food throughout their lives. If a bird’s first nesting attempt is not found and gobbled up by a vertebrate predator, a second one at the same site will likely escape predation as well. On the other hand, a raccoon, blue jay, or rat snake that found and ate your eggs at one site in mid-May will likely do so again in June, if you reuse the nest site. By moving away from the site of a failed nest, you might find a new site that does not fall within the predator’s home range – or is better hidden or otherwise inaccessible to the animal – and the prospect of successful breeding is renewed. That is the simple beauty of the WSLS rule.

While predation is the most obvious and important reason for using the WSLS rule, there are other reasons why moving a nest might be beneficial following failure. A species like the cliff swallow, whose nests become infested with swallow bugs – blood-sucking insects that attack and kill nestlings – should (and does) respond to infestations by moving the nest. The key point: vertebrate predators and tenacious parasites are persistent and location-specific nesting threats. To place a new nest at the same spot shortly after losing a first one to such a threat is to court disaster.

The WSLS rule has been confirmed as a logical and successful nesting strategy by ecologists around the world. Numerous theoretical papers have been written about it (including one by me). The rule is so widespread that scientists often think of it as “the way” that birds respond to nest failure. But closer inspection of nest failures shows that we have oversimplified the picture.

Nest failure can also occur owing to threats that are fleeting and non-location-specific. Fleeting, non‑location-based threats are those that occur at a brief moment in time, are not likely to recur soon, and are no more likely at one location than another. Examples are “freak” weather events, like early spring snowstorms or heat waves. Fleeting threats of this kind usually end quickly – so quickly that they abate before the nesting pair can even lay a new clutch of eggs. Fleeting threats make very different demands on nesting birds than do persistent threats and should be countered with a different strategy. Why? Think of a pair of loons whose nest has been flooded by a 6-inch rainstorm. If the pair were to use the WSLS rule to respond to this fleeting threat, they might move their nest away from a traditional nesting location (say, a favorite island) that they had used to produce many fledglings in years past and choose a new, untested nesting location. In so doing, the pair would discard years of accumulated knowledge about their territory and  dim their breeding prospects.

What is the proper response to a fleeting threat of nest failure? Nothing! That is, the logical and adaptive response (i.e. that which maximizes the chance of breeding success) is to ignore fleeting causes of nest failure and consider the next nesting attempt a “do over”. Do birds have the capacity to respond differently to different causes of nesting failures? It is too soon for a general statement, but loons can do so. If a predator gets their eggs, loons use the WSLS rule (i.e. they move the nest). If a fleeting threat causes them to abandon their eggs, loons ignore that nesting attempt, often placing a new set of eggs right back in the same nest they started and abandoned a week or so before.

Followers of the blog will know that loons face a fleeting (but very severe) threat to nesting that most other birds do not: black flies. Perhaps their vulnerability to black flies — which typically only cause nest failure for a week or so in late May —  has caused loons to evolve a more sophisticated response to nesting setbacks than other birds. I have begun combing through the literature on avian renesting behavior in order to determine if, indeed, the nuanced renesting behavior of loons is unique. Since I have just started, we can bask for the moment in the possibility that loons are a cut above the rest.

Loons are always with me. With its fires, mudslides, and Mediterranean climate, southern California could hardly be more different from northern Wisconsin, but the loons winter here. I see them at Newport Pier, a bustling wharf that juts out into the Pacific and draws scads of Vietnamese anglers…..and me. The chattering fishermen are after pacific mackerel, which feed beneath the wharf in great whirling clouds. I am looking for pelagic birds that might fly by, like red-footed boobies, pomarine jaegers, and common murres. But I always see loons too. In fact, common, pacific, and red-throated loons all occur along the coast of southern California in good numbers.

My first sighting this morning was auspicious; I spotted a fast-flying parasitic jaeger as I reached the end of the pier. Small pods of common dolphins surfaced at intervals as they too pursued mackerel, exciting the gulls and pelicans near them. Great rafts of western and Clark’s grebes stretched out north and south of the pier. Experience told me that these circumstances were likely to produce a rare bird sighting.

As I completed my initial scan of the water adjacent to the pier, I saw a common loon with a buoy near it — at least, the odd dayglow-pink item near the loon registered as a buoy on my first glance at it through my spotting scope. (A photo taken with my phone through the scope appears above.) As I studied the loon and pink item further, I realized it was a bobber connected to one of the legs, because it followed along a foot behind and bobbed up and down rhythmically as the bird swam slowly along the surface. I groaned. Even in winter, apparently, loons face fishing entanglements.

My relaxing birding trip at an end, I watched the loon for an hour to learn how it was coping with the fishing gear. Fortunately, it swam southward during this period, which, bit by bit,  brought it closer to the pier. Despite the cheerful fishermen whose casts and puttering about blocked my view at intervals, the loon was simple to track. Early on, another common loon approached and preened within a few meters. The entangled loon remained alert but showed no other obvious response. Similarly, it ignored a smaller pacific loon that came near while diving. A second common loon came over and showed a hint of social behavior, such as we see in the breeding season. For a third time, the loon with the bobber made no response. The bird did not even react noticeably when a juvenile western gull flew over, settled beside it, and began to pick at the bobber. At all times, the entangled loon sat high in the water; it never dove, preened, or even gave a wing flap.

The lack of social interaction, disinclination to dive or exhibit other normal loon behaviors, and posture of the loon in the water speak volumes about its condition. These signs indicate that it has probably been dragging the unwanted bobber for some days and is severely impacted. Fortunately, bald eagles, the loons’ nemesis during summer, are rare in southern California, so the loon is not likely to succumb to predation. But its inability to dive means it has already begun to lose weight and become weak. It will surely starve if the bobber is not detached soon. I will visit the pier tomorrow to see if I can relocate the bird. If so, and if its status appears unchanged, I will see if I can put together a capture team. With great luck, we might free the doomed bird.

 

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.

As my family and friends will tell you, I am judgmental. When an event happens that could be attributed to mindless error, I am inclined to view it, instead, as deliberate selfishness or irresponsibility. I derive my hypercritical worldview in part from my profession. As a behavioral ecologist, I presume that much of the behavior we see in animals (including humans) has evolved in order to promote their evolutionary fitness. Put another way, I assume that a good deal of animal behavior is selfish — evolved because it allowed the ancestors of living individuals to survive better and leave more offspring than others of their species.

The presumption of selfishness is a helpful touchstone in my field. It provides a starting point when one is interpreting a new and unexpected behavior pattern. For example, if I notice a new soft call emitted by female loons during courtship, I am apt to hypothesize that this call might help mates synchronize their breeding activities so that each will be prepared to do its share of the incubation duties, once eggs are laid. (Such synchronization, which involves rising prolactin levels in the blood, has proved crucial to successful breeding in many species of birds.) So the presumption of selfishness can  be a useful prism through which to understand animal behavior.

A week ago, the folks at REGI learned of an event that pushed even my cynical viewpoint to the limit. Following a report from a lake resident, they found an injured loon on Metonga Lake, which is just south of Crandon, Wisconsin. After Linda and Kevin Grenzer captured the loon (pictured in Linda ‘s photo above) and the REGI team examined and x-rayed it, they learned that it had been shot at close range with a shotgun and had lead shot throughout its body. Despite efforts to save the unfortunate shooting victim, it died in their care. The story might have ended there, except that the loon was banded.

Since Metonga is outside of our study area — some 20 miles east of our southeasternmost lake — we do not know the lake at all. Sleuthing by Linda and me revealed that this oval 2000-acre waterbody supported two breeding pairs in 2018. According to the loon ranger, both pairs hatched chicks this year, although only one of the pairs fledged their two hatchlings. Most important, neither pair contained a banded individual. Thus, the shooting victim was not a member of either resident pair.

Some of the circumstances surrounding the tragic shooting make sense. As many of you know, breeding loon pairs become restless in September and October, often leaving their territorial lakes. Moreover, large, clear lakes like Metonga are favorite spots for wandering adults to visit, as they forage intensively and lay down fat stores to fuel their southward migration. So it is not at all surprising that a breeding adult from a neighboring lake — as we presume the victim was — would be found on Metonga. Finally, virtually all of the loons that we band that show up that far from our study area are females, because females are the more dispersive sex. (On average, females settle 24 miles from their natal lake, while males settle 7 miles from their birthplace.)

The identity of the shooting victim allows us to speculate about its tragic end. When I looked up the band colors and partially-obscured USGS band number that Linda provided, I learned that we had banded this female nine years ago as a chick on Bear Lake in Oneida County. We have not seen her since. The father and mother of this female were among the most approachable loons in the study area. (The male still holds the territory there, as he has since 2001 or earlier.) As Chapman student Mina Ibrahim showed a year ago, tameness (the minimum distance that a resting loon will permit a canoe to approach before diving) is similar between parents and offspring. So it is almost certain that the dead female was a tame individual, like both of her parents.

If our simple inference is correct, then this incident has exposed one hazard of extreme tameness in loons. While the vast majority of humans who approach loons closely are merely curious and would never dream of harming them, an occasional human might do so. It is easy to reconstruct the chain of events that led to the shooting. In the opening week of duck season, a hunter got an easy shot at a duck-like diving bird and took full advantage.

This analysis might well be correct, but it has one hitch. Loons are so well-known across the heart of their breeding range that they can scarcely be confused with ducks. None of the species of ducks that a hunter in northern Wisconsin would be looking to bag is patterned much like a loon. Furthermore, all duck species in the area are far smaller than loons and are prone to fly, not dive, when approached by humans. And since we know that the hunter blasted this loon from very close range, it is even more difficult to believe that the incident arose from a misidentification.

Call me cynical, but I believe that the hunter who killed this loon was not foolhardy, as generous and forgiving people might believe, but rather purposely wicked. Of course, this conclusion further erodes my opinion of other humans. What kind of person deliberately shoots a loon?

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.

 

Recently, I made the kind of finding that gives scientists fits. It came about in the same manner that findings often do initially: a hunch.

Since I spend much of my life either working closely with loons or poring over data that describes their breeding success, I am in a good position to notice subtle changes that occur over time. Occasionally when out on a lake, I observe a breeding event and think, “Wow…..that did not happen in the old days!” Then I retreat to my computer, look at data from years past, and see if I am correct. I have to confess: in many cases, I am wrong.

Slide1

This past August, I noticed what I thought might be a growing pattern in breeding ecology. Mated pairs, it seemed to me, were less often rearing two chicks to fledging. That is, they were either hatching one chick and rearing the singleton only or hatching two chicks and losing one. At least that was my impression. In this case, field data confirmed my suspicion, as the above graph shows. The proportion of singleton broods has risen during the study. In three of the past five years, in fact, two-chick broods were quite uncommon, making up only 1/5 of all broods. Most of the pattern, moreover, appears to result from failure of one of two eggs to hatch, rather than loss of the second chick after hatching.

Faced with a puzzling and unexpected finding, I looked immediately at the usual suspects. Black flies, which have also been worse in recent years, are an obvious possibility. Flies harass incubating loons, reduce incubation times, and might reduce hatching success. In fact, I was convinced when I wrote our recent paper that black flies were the culprits. But then 2018 happened. This season featured a warm spring, a rapid die-off of flies, and very few fly-induced abandonments. So we could not blame flies for the low hatching rate of eggs in 2018.

What about the changing climate? As I have emphasized in a recent post, warm weather is projected to drive loons northwards; could it also be the root cause of the lower hatching rate? I looked to see if warmer May temperatures are correlated with reduced hatching, but they are not. (In fact, warmer temperatures are associated with a slightly higher hatching rate.) Likewise, precipitation might, in theory, reduce hatching rate. Again, years of higher May rainfall were not years of lower hatching success. I breathed a sigh of relief to learn that the lower rate of hatching does not (preliminarily) appear to represent the harmful leading edge of climate’s impact on loons.

Two possibilities remain. First of all, there is a small chance that the pattern is a statistical anomaly — that hatching rate is not actually falling, but that the result occurred by sheer chance. Scientists must always be circumspect about their results, and the statistical test says that there is a 0.6% chance that the finding does not represent a true pattern. (That is roughly the likelihood that you toss a fair coin 9 times in a row and get “heads” every time.) Second and more likely, some unknown factor is at work here. Might there be an environmental contaminant, picked up by loons, that increases developmental abnormalities in embryos or perhaps causes adults to cease incubation of the second egg prematurely? Might disturbance of incubation by humans be the cause of lower hatching success? These possibilities — and numerous others — generate testable predictions, and I will test them. In the meantime, let’s all keep our fingers crossed that the distinct decline in loon hatching success over the past 20 years is, after all, just a blip.

 

 

 

Humans are not good at thinking about the distant future. We are not alone in our short-sightedness. Living things, in general, are obsessed with the here and now and oblivious to what lies far down the road. There is a very good evolutionary reason for focusing on the present. Animals that succeed at surviving and protecting their progeny leave more young than other animals (in this case, hypothetical ones) preoccupied with what conditions might be like for their grandchildren and great-grandchildren. Animals that attend to their own survival and that of their offspring simply leave more offspring. Thus, natural selection can be said to favor animals that focus on the present — and animals within natural populations are chiefly descendants of parents and grandparents that cared for their own survival and that of their offspring. The short-term view makes sense evolutionarily.

Our very logical tendency to heed the here and now at the expense of the future has a limitation. Focus on the present adapts animals well to a stable environment, but leaves them poorly adapted to an environment that changes rapidly. Over evolutionary time, environmental change has generally occurred slowly enough to cause little problem for animals that live only for the present.

But humans have hastened environmental change. Anthropogenic changes have taken many forms, including introduction of invasive species, environmental degradation, and wholesale alteration of landscapes and vegetation. Perhaps surprisingly, many non-human animals have been able to keep pace with human impacts. In fact, some — crows, gulls and raccoons come to mind — have benefitted enormously from human activity. Others, of course, have become extinct, endangered or have seen their geographic ranges contract because of humans. We could quantify human impacts of each and every non-human species, if we cared to, and place each on a chart from least- to most-impacted.

Where on the chart would the common loon fall? Considering that loons are often viewed as the “voice of the wilderness”, one might suppose that they would suffer greatly from human encroachment. In fact, loons are hanging in there better than many other vertebrate animals. Knocked back in the middle of the 20th century, the common loon population has rebounded. Breeding populations are now generally stable or even increasing across most of the northern tier of United States. My study area in northern Wisconsin is typical; loons have re-colonized many lakes in the past few decades from which they had retreated. So loon populations are thriving despite extensive shoreline development, entanglements with hooks and fishing line, and increases in methylmercury levels, among many other challenges.

A new anthropogenic threat now looms that is more extensive and unrelenting than others that loons have faced. Climate change has already caused many geographic ranges of North American animals to recede northwards. A recent study showed that bird species differed greatly in their northward shifts, but that, on average, breeding ranges are marching northwards by over 2 km per year. We have a bit of an apples and oranges problem here; the bird species included in the study varied greatly in their diets and habitats. Some, no doubt, are highly dependent upon temperatures (and related factors like vegetation) for their survival; others are not. So it is difficult to project precisely how the geographic range of the common loon might be affected. But do this: take a look at Audubon’s animated depiction showing the contraction of the loon’s breeding range.

Two patterns are immediately clear from the animation. First, the northern Wisconsin loon population (and abutting populations in Minnesota and Michigan’s Upper Peninsula) exist on an isolated “finger” that projects southwards from the heart of the range, which lies in Canada. Second, the model paints a very bleak picture of the future loon population in northern Wisconsin. According to the model, loons are projected to be much less abundant in northern Wisconsin by 2050 and gone altogether by 2080.

Now, a word of caution. Audubon scientists have attempted to distill the climate down to two main factors: temperature and precipitation. On the basis of these two climatic factors, the current distribution of the species relative to these factors, and the projected future climate based on the report of the Intergovernmental Panel on Climate Change (IPCC), they have produced the  animated graph that loon enthusiasts like us find so disturbing. Their projection is likely to provide a crude estimate of the impact of climate change on loons, not a precise one. That is, loons are likely to cope with climate change better than most other birds — as they have other environmental threats. Then again, loons might be especially sensitive to climate change and retreat northward more rapidly than the study predicts.

Like many other humans, I am obsessed with the day to day. I have studied loons as if they would be around forever. I have battled to obtain grants to keep my study afloat, to publish my papers in high-impact journals, to hire diligent field technicians who would collect reliable data. Now, forced by changing environmental conditions to glance towards the future, I can scarcely believe that the animals that I have learned so much about and grown so fond of might be well on their way to vanishing from Wisconsin in my lifetime.