Pondering Tameness

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Since the inception of the study, we have known that some adult loons permit a canoeist to approach to within 5 meters without alarm, while others become uneasy and dive at a distance of 30 meters or more. Over the past several years, we have worked hard to quantify such variability in “tameness”. Our efforts are motivated by the belief that — in a region well-known for human recreation — tameness must matter. That is, it seems inconceivable that loons’ survival rate and reproductive success are not impacted by the way they respond to humans.

At first blush, I would expect loons to have higher fitness (i.e. be able to survive and breed more successfully) if their tameness reflects the lake they inhabit. That is, loons that are very tame should fare well on lakes where humans are numerous and often approach loons closely. A skittish loon on a lake with abundant human traffic would spend a great deal of time and energy avoiding humans and might have to spend more time foraging to compensate for the extra energy expenditure. A skittish individual on a busy lake might even become distracted by humans and pay too little attention to eagles, which occasionally attack adult loons and often attack chicks. On the other hand, shyness towards humans should have no impact on fitness if it occurs in a loon that occupies a remote lake.

Tameness is surprisingly vexing to measure. While it is easy to see that loons vary in approachability by canoe, it is another matter to assign a number to the degree of approachability they show. One obstacle to measurement is simply that of measuring distances accurately across water. Another is the problem that we seek to know exactly at what approach distance a loon dives to avoid a canoe; once this critical distance has been reached, the loon has left only its wake on the lake’s surface for us to measure! After numerous trials, however, Seth Yund, a Chapman student, and I have found a technique that seems to work that requires use of a highly accurate laser rangefinder — and a lot of patience. In July we began to collect measurements on each banded loon in our study population, and this work will continue into the fall and in future years. (By the way, the technique requires paddling slowly in a canoe towards a resting loon until it dives, while taking constant measurements. Since the process must only be carried out once or twice per loon, it involves very mild disturbance. We have found that loons quickly resume normal behavior after we take a tameness measurement.)

It will be some months before we begin to see if our quantification of tameness is stable and consistent enough to constitute a useful behavioral measure. At that point, we can begin to test our preliminary hypothesis that a loon’s tameness should be correlated with amount of human usage on its lake. Since we have many parent-offspring pairs in the population and follow individuals throughout their lives, we can envision asking questions about the heritability of tameness and its constancy over time. We hope that tameness will become a rewarding topic of research for us. Perhaps our ability to quantify this behavioral characteristic will permit us to foresee negative impacts that increasing human-loon contact will have on our population and help recommend ways to minimize such impacts.

What We Know, and Don’t Know, about Territorial Intrusions

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A few days ago, I was conducting observations on the lake where Linda Grenzer lives when she snapped this photo of me, the two pair members on the lake (the two loons closest to my canoe), and five territorial intruders. Linda’s picture captures beautifully what transpired during my visit of an hour and a half. Better yet, the photo shines a spotlight on an enduring question that drives much of my research on loon territoriality: what is the purpose of territorial intrusion. This is a question that we have only half-answered.

We do know that many intruders visit in order to learn whether or not a territory has chicks; if they detect chicks, they are more likely to intrude in the following year and attempt to evict the breeding pair member of their sex. (This makes some sense, as the presence of chicks is an indication of good nesting sites and plentiful food for young.) We also know, from a recent analysis, that loons practice natal-site matching; that is, they attempt to settle as a breeder on a lake that is similar in physical size and in pH to the lake they were reared on. So undoubtedly some intruders must be learning about lakes where they intrude so that they can settle on one similar to their natal lake.

But there must be more motivation for intruders to visit lakes defended by breeding pairs. Among the 5 intruders pictured in the photo, for example, were: a banded 9 year-old loon not known to be settled on a territory yet (i.e. a probable “floater”), an unbanded loon whose status is wholly unknown, and three banded loons known to be members of breeding pairs from neighboring territories. While the first two birds could plausibly be shopping for territories through chick detection or natal-site matching, the neighbors are unlikely to be doing so.

What, in fact, could neighbors stand to gain from intruding next door? Several hypotheses are possible here. Neighbors might gain by becoming familiar with other loons with which they might become mated in the future, if they both lose their current breeding positions and must settle elsewhere in the general area. Neighbors might also be trying to learn about the territory, which they might occupy in later years, providing one of the current pair members dies. Another possibility is that neighbors have no particular interest in the territory where they intrude but, rather, are intruding in order to draw attention away from their own territory (since loons on the water tend to attract flying loons to land and investigate). That is, intruders might be attempting to “decoy” loons away from their own territory so that others do not learn about it and attempt to settle there. Finally, neighbors might simply visit to forage in someone else’s territory, depleting the food supply there instead of at home.

An additional question raised by the photo is: what is the breeding pair’s response to intruders? One might expect that the breeders would react aggressively towards intruders, driving them out immediately so that they cannot learn about their chicks (of which there were two in this case, hiding our near shore and far from the intruders) or harm them. Yet this pair — typical of breeders — was tolerant of the intruders and allowed them to roam freely throughout the territory for over an hour. Are the breeders feigning nonchalance to reduce the likelihood that intruders will look closely for and detect the chicks? Or do large numbers of intruders pose a severe threat to territory ownership such that territory owners must tolerate them or risk losing their positions?

I hate to raise so many questions that we cannot answer immediately. Testing of most of these hypotheses for intrusion and defense towards intrusion is feasible in our population. For example, we can look statistically at the “decoy” hypothesis by seeing whether pairs that vacate their territories and intrude next door experience a lower rate of territorial eviction than pairs that remain on their territories faithfully throughout the season. And we can test whether pairs that attack and stalk intruders, rather than tolerating their intrusions peacefully, suffer a higher rate of territorial eviction, because they betray the presence of their chicks and place a target on their own backs.

Such statistical analysis requires large samples of lakes and intrusions, so it will take time. Meanwhile, we will have to enjoy the experience of tracking intruders and breeders around territories by canoe and wondering what peculiar combination of evolutionary interests of breeders and intruders could produce such flotillas.

 

A Bit of Cheer amidst the Gloom

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By any reasonable measure, 2014 has been a dreadful year for loon reproduction. Even if we capture every remaining loon chick that we know of, our total number banded will be almost exactly half of last year’s total. Clearly, the black flies hit the loons’ breeding efforts in the mouth, and they could not recover. Still, it is only one year. As my work has shown me over the past two decades, breeding success is a roller-coaster. In fact, if you combine last year’s bumper crop of chicks with the withered output of this year, the message is that loons are producing enough chicks to sustain the population. So all is not lost.

There have been a few bright spots this year. Though we were alarmed in early June when the Jersey City Flowage male ingested a fishing lure and became hopelessly entangled, the folks at REGI were able to save the bird, he was released near his old territory and recovered — except for possession of his territory! The REGI folks were brought an emaciated chick found by a roadside that they fed back to reasonable health and that we were able to foster successfully to a loon family that has raised it as their own. We recently banded both this fostered chick and its sibling, a true biological chick of the pair. Both chicks have become big healthy, strapping young birds, thanks to their parents’ tireless efforts.

In short, life goes on. I am confident that we will long remember 2014 and not wish to repeat the experience. But perhaps we should best remember 2014 as a year that, while dismal for chick production, was balanced out by strong reproductive years surrounding it and did not pass by without a few cheerful tidings.

Former Male Breeder on Jersey City Flowage is Back in the Game!

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Good news has been scarce this year. Black flies snuffed out first nesting attempts by virtually all breeding pairs and will reduce chick production by about 40%, compared to last year. One of the few pairs to continue incubating in defiance of the flies hatched chicks, only to lose them to infanticide when a new young male evicted the male breeder. And one of our most consistent chick producers and well-loved birds, the 19 year-old male on Jersey City Flowage, barely survived severe entanglement in fishing line that caused him to lose 20% of his body weight.

A few days ago, we received a bit of good news. The Jersey City Flowage male, after surgery and rehab work done by the folks at REGI and release near his original territory, has not only shown the capacity to feed himself normally, but has re-paired with a female hatched on Fisher Lake in Vilas County in 2010. This May-December pair seems settled at the north end of Jersey City Flowage, according to Linda Grenzer. Now, whatever judgements we are tempted to make about the age disparity in this relationship, it is nice to see the old male get himself back in shape and ready to give life another try.

The Lasting Impact of Black Flies

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Since 2014 marked by far the most intense explosion of black flies in recent memory, I wanted to look at how loons are faring reproductively this year compared to last. It has now been over a month since the peak of “black fly season”, which was miserable for loons but lasted only about a week. Yet the flies were thick enough and their outbreak coincided so closely with the start of incubation for most pairs that about 70% of all loon pairs in our population abandoned their nests.

It seemed certain that the epic abandonment of early nests in 2014 would negatively impact the number of chicks produced by our population. And it has. Based on my analysis of 96 territories covered in 2013 and 2014, I have the following results. Last year, 41 pairs  had hatched chicks by 30 June, while 14 had nests close to hatching, 10 had early nests whose outcome was uncertain, 21 pairs had failed for the year, and 10 pairs had never nested (to our knowledge). In 2014, the numbers were 6 chicks, 30 promising nests, 15 early nests, 21 failed pairs, and 14 pairs without no nest during the season.

The disparity in chicks produced is alarming, of course. This is the most important number. The picture gets a bit rosier when you crunch the numbers and recognize that many pairs currently on nests will eventually hatch chicks. Based on an assumption of 70% hatch rate among pairs in the “likely hatch” group and 40% in the early nest stage — perhaps slightly optimistic — the total estimated chicks produced in 2013 and 2014 are 54.8 and 33.0, respectively. To put it another way, about 57% of all pairs reared chicks in 2013; 34% will in 2014. This is a decline of 40% in the number of territorial pairs producing chicks.

Now, we need to step back here. Loons are long-lived animals, and most pairs that failed to raise chicks, owing in large part to black flies, will try again next year. So, in the big picture, the decrease in rate of chick production is not so awful. In a few more years, we will look back on 2014 as just a worse-than-average year for loon chicks, not a year that threatened to end loon life as we know it. But it is hard to be very upbeat at the moment.

Elation….then Devastation on West Horsehead Lake

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After the black fly debacle in recent weeks, we were all ready for some good news. Indeed, most territorial pairs had shaken off the flies and gotten back to the business of reproduction. Good tidings seemed the order of the day. Yesterday, Al Schwoegler of West Horsehead Lake called with a thrilling and unexpected report: the eggs laid by the pair, which they had left unattended for many long hours on several days because of the torment of black flies, had begun to hatch! At first neither Al nor I could believe that the eggs were viable. As Al described the behavior of the female on the nest — who has reared a whopping 19 chicks to fledging since 1996, when she was first banded — we gradually let ourselves believe that the impossible had occurred.

But our positive feelings were dashed suddenly by the cruel realities of loon territorial behavior. You see, the last few weeks at West Horsehead have been marked by frequent territorial intrusion. At the very time that the pair was trying to recover from the onslaught of biting insects, the male owner was facing repeated challenges for his position. Finally, by yesterday, both Al and Sally Yannuzzi of my team confirmed that male ownership had passed from the 14 year-old male hatched on Alva Lake who had resided on the lake for most of the past decade to a 9 year-old upstart from Harrison Lake in Lincoln County. The new male, confident in his new position, spent much of the morning resting and foraging near the nest, while the female patiently sat on the eggs. Finally, the female slid off of the nest into the water, revealing a newly hatched chick and second egg, which was on the brink of hatching. Alas, the new male behaved as animals typically do when confronted with helpless young that are not their genetic offspring: he quickly pecked the chick to death as its mother looked on helplessly. The celebration of an unexpected hatch gave way to a wake for a young loon doomed by territorial usurpation. Al took this photo of the female, still mildly protective of her nest containing the dead and unhatched chicks. (Shortly after the photo was taken, the female left the nest to forage with her new mate, with whom she might still renest.) IMG_20140616_134217_724Sorry for the unpleasant photo and description. But there is a valuable lesson here. Loons, like lions and langurs and mice and water bugs, behave so as to promote their own reproduction. Despite the ugliness of this episode, we can hardly hold it against the 9 year-old that he is looking to produce his own biological offspring — before a new usurper comes along and shows him the exit.

The Downside of Dual Incubation and a Ray of Hope

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To be sure, 2014 is shaping up to be a dismal breeding season. Ice-out occurred weeks later than usual, owing to thick ice and cool weather in March and April, and delayed breeding for all loon pairs. The ensuing warmup in May caused the black fly population to explode to higher levels that we had ever seen. Pairs that had just laid eggs were blanketed by the relentless bloodsuckers and incubating males and females driven off their nests at rates never seen before. In short, almost all loons abandoned their first nests.

Although it is counterintuitive, loons are probably more vulnerable to nest abandonment than many other birds because males and females incubate the eggs equally. Consider the plight of loons trying to incubate their eggs to hatching for 27 days in the presence of black flies. Each pair member must incubate for stretches of several hours before being relieved by its mate. The rotation system must be efficient enough that eggs are incubated over 99% of the time. When not sitting on eggs, a breeder rests, preens and forages to replenish its energy reserves. If either pair member fails to incubate, the nest is doomed to failure, because its mate cannot compensate for missing incubation by remaining on the eggs at all times without long breaks for foraging. So we have a case where the weakest link breaks the chain. Even a tough, determined male incubator is destined to lose a clutch if his mate is less determined than he is and refuses to sit on the eggs and tolerate the torment of biting insects.

We have learned about the necessity of dual incubation from past observations. Nest abandonment commonly occurs following territorial eviction of a pair member during incubation. If its mate is evicted by an intruder, the remaining pair member usually continues to sit on the eggs for a time. With rare exceptions, though, its new mate (the usurper) does not incubate — why should it sit on eggs containing young to which it is unrelated? — the cycle of shared incubation duties breaks down, and the nest fails within a day. (If it is early enough in the season, such pairs will lay a new set of eggs that both will incubate.) A rarer cause of nest failure during incubation is death of a pair member. In 2005, the female on Alva Lake was killed by an eagle while sitting on the eggs. The male valiantly sat on the eggs, taking breaks to forage from time to time, even as female floaters competed in front of him to fill the breeding vacancy. Despite being within a week of hatching, this male could not complete incubation on his own, and the nest was lost.

Enough talk of failure! I will end on an up note by showing you the sweet photo that Linda Grenzer took of a breeding male sitting on a nest. This bird and his mate both tolerated the record outbreak of blackflies earlier in the season and were rewarded with a little fuzz-ball — a much-needed reminder that all is not lost this year. Let’s cross our fingers that other pairs, many of which are incubating a new clutch of eggs after abandoning the first, will be able to duplicate this effort.

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So Far, So Good!

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Sorry for the posts on back to back days, but I wanted to report on the status of the Jersey City Flowage male, released four days ago. He is looking healthy and diving normally, it seems, as this photo by Linda Grenzer suggests. Thanks, Linda, for tracking him down!LMG_0964

He has moved about a mile in the large lake where he was released, and has skirted the territory of a pair that nests in the lake. So, while it is far too early to pronounce him out of the woods, things are looking promising. It is remarkable to observe the severe injuries from which loons can recover. Let us hope that this bird — who has both the brightest bands in the study area and the calmest disposition — can add to the short list of loons that have flirted with death following fishing entanglement, been captured and disentangled, and recovered to become territory owners again.

 

Another Territorial Male Victimized by Fishing Tackle

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Now…I am a long-time fisherman. Since I was a young boy, I have enjoyed throwing a line in the water and imagining the lunkers waiting to strike my lure. (I think it started with McElligot’s Pool, the fantastic Dr. Seuss book that my parents read to me and my sibs.) I have spent many fruitless hours fishing — and enjoyed every minute of it. But my lifelong love of fishing has taken some bruises lately, as it has become increasingly clear that many loons in northern Wisconsin die horribly each year after entanglement in fishing line. I discussed some such incidents last year, but we have already had a recurrence of the problem this summer.

The most recent casualty is the territorial male on Jersey City Flowage. We had become rather fond of this bird, whom we banded as a chick on Swamp Lake in 1995. Year after year he and his mates have reared chicks on the Flowage, taking advantage of the abundant marshy habitat and network of islands there. He is tame, permitting us to approach closely and identify him whenever we care to. I vividly recall an occasion in 2005, when I found him foraging with his big strapping chicks. Neither he nor his juveniles cared a whit when my canoe approached them. They all foraged peacefully, oblivious to me. Here is a photo — a rather poor one — that I took Image

of the foraging family on that day.

Our team noted a month ago that the male had not returned to his territory in 2014. We were disappointed at the loss of cherished individual, but accepted that he had died over the winter or on migration or, perhaps, been evicted by another male this spring. Such are the perils faced by loons. But Marge Gibson of Raptor Education Group, Inc. notified us last week that her group had picked up a badly injured and emaciated male from a lake near Tomahawk, Wisconsin which turned out to be this male. He had swallowed two lead sinkers and, as you see, had become irrevocably entangled in the attached monofilament line.  Image

Although this bird had lost 25% of his body weight (down to 3400 g from his normal 4500 g) and was in desperate shape, Marge reports that the REGI staff were able to disentangle him, remove the lead sinkers, and get his weight back up to 3800 g with vigorous feedings. They were also able to repair his bisected tongue and restore blood flow to it. Recently, he was released near his old territory. Although it is always tricky to rehab a bird in such a weakened condition, we are allowing ourselves to hope that he will recover and will let you know what we learn of his health and territorial status. (He has lost his territory, and the new male there and his mate are nesting, according to Linda Grenzer, our tireless citizen scientist. So it will be a long road back for the injured male, even if he does return to health.)

I think that I will always enjoy the unique mixture of natural beauty, solitude, and occasional surge of adrenaline that I have enjoyed while fishing. But I will never again use lead tackle, especially now that there are many appealing alternatives. Help me spread the word about them!

The Scourge of Blackflies

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As this searing photo by Linda Grenzer demonstrates, blackflies are making incubation miserable for loon pairs this spring. Actually, this guy — a 16 year-old male from Muskellunge Lake — is hanging tough despite dozens of the remorseless bloodsuckers. Where blackflies infestations are worse still, such as the hundreds we have seen swarming around nests on Bobcat and Upper Kaubashine lakes, loons abandon their nesting attempts altogether. Based on visits to dozens of lakes this spring, it seems that about 70% of all loon pairs that have started

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nesting have been unable to incubate owing to blackflies. This is much the highest rate of blackfly-induced abandonment that I have seen in 22 years of loon study. (32% was the worst rate before this year.) These dipterans are such a nuisance that they even cause loons to change their daily activities. Normal adults spend lots of time oiling their features, preening and resting, but those terrorized by the tiny flying demons spend virtually the entire day diving, surfacing to take a breath and shake their head free of blackflies, then diving again. Luckily, most pairs that abandoned their nests due to blackflies did so within the first week of incubation. Thus, they still have plenty of time to renest, which most will do soon.

While loons are no doubt the most serious victims of blackflies, the tireless arthropods impact field observers as well. You see, preening and resting are the two activities of loons that make it easiest to ID individuals. Since loons have reduced or eliminated preening and resting from their activities and, instead, begun to dive incessantly to avoid flies, we have a devil of a time getting close enough to individuals to identify them from their colored leg bands. (Loons have even shortened the resting time between dives to reduce their exposure to blackflies.) So, we too look forward to the end of a brutal year of blackflies.

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