Walter Piper

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The goose population has been increasing in northern Wisconsin. Ten years ago, a Canada Goose was an infrequent sight on one of our study lakes. Geese were confined chiefly to a few large lakes and seen overhead only as they migrated northwards. But no more. Now we encounter adult geese and often pairs with goslings on about half of our study lakes.

Apparently the increased availability of waste grain from agriculture, the proliferation of lawns, and increased temperatures have fueled the explosion in goose numbers, which has the potential to impact loon reproductive success. You see, geese and loons both prefer nesting sites safe from mammalian egg predators like raccoons and foxes. Such sites are often on islands and are limited in number. If a small island offers the only available safe nesting on a lake, goose and loon pairs are both likely gravitate to it.

The problem is not merely that loons must now compete with geese for nesting sites; geese actually get “first dibs”. While both loons and geese incubate their clutches for about four weeks, geese initiate their clutches two weeks or so in advance of loons. (The earlier onset of goose nesting is evident right now in our study area, as many goose pairs are rearing their broods of two to six goslings, while the earliest loon nests will not hatch for another week or ten days.) On occasion geese and loons nest within a few meters of each other on islands — as we observed on Oneida Lake a few years ago. Coexistence between the species is possible. But the presence of a sitting goose appears to discourage loons from nesting nearby, which often forces loon pairs to select sub-optimal sites for incubation.

Consider the plight of the Clear Lake loon pair. The safest, most desirable nest location on Clear Lake is a small shrubby island off of the public boat landing. Loons have shown a strong preference to nest on this island during most years. This year, the geese got there first, and the loons had to settle for a new nesting location on a long peninsula about two kilometers south. They may hatch chicks off of this peninsula, but the site is not offshore, like the shrubby island, so it is clearly vulnerable to mammalian egg predators.

I am optimistic that this spunky loon pair will be able to pull off a hatch. As can be seen from our shaky video, the male (on the right in the video) is still working on improving the surrounding nesting area, and the pair has a well-constructed nest with two eggs (visible to the left of the female, after the camera pans left). Still, this well-constructed nest will not protect them from a scavenging raccoon that ambles by.

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It is late May again. With nesting underway, loons must confront the first of many hazards that stand between them and successful parenthood. Simulium annulus are blood-sucking black flies that attack common loon specifically. In a good year, they make life miserable for loons, forcing them to increase their diving frequency and decrease preening and resting — simply to avoid spending time on the surface, where they are at the mercy of the flies. In a big fly year, like 2014, black fly infestation can cause 70% of all first nests to be abandoned.

While we can understand how bites from flies would make life miserable for incubating loons, why should loons — like the male above photographed today on Tom Doyle Lake — leave their nests? Like many problems in biology and life, this involves a trade-off. A loon that incubates in spite of relentless attacks from black flies can hatch chicks from the nest. But tenacious incubators also face a high threat of blood-borne parasites from the flies, which might weaken them and shorten their lives. On the other hand, a loon that punts on its incubation duties in the face of the flies will lose that nesting attempt but be able to renest two weeks or so later, when black flies are all but gone. Although this delay lessens the chance of producing chicks for the year, it might make sense to a bird that must take a long-term view — favoring health and condition, rather than risking disease for a slightly greater chance of producing chicks.

As I was writing this last passage, I realized that this is yet one more case where we might expect the age of a breeder to have an impact on incubation behavior, based on senescence theory. An aging loon that stands to have only another year or two on its territory might well have greater fitness (i.e. lifetime chick production) by investing heavily in the current breeding year, rather than preserving its health for a future year that might never come. So we might expect male loons, which senesce mightily, to be tenacious incubators during their waning years. (In contrast, young males should readily abandon a nest, when black flies become thick.)

I will certainly look at the data to see if age has an impact on male incubation behavior; I am excited to do so. But there is a catch. As I have noted in a previous post, dual incubation by both males and females muddies the water. That is, we might expect that an old male would boost his eggs’ chances of hatching with heroic incubation during a heavy black fly season, but such a male is unlikely to be able to compensate fully for a mate that refuses to incubate. So at best we might expect that an old enthusiastic male incubator might decrease likelihood of nest abandonment by an amount great enough to justify his efforts.

I will let you know what I find out.

 

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Sleet greeted me as I landed yesterday at Rhinelander Airport. Since I had come from 75 degree southern California, it took me a few moments to adjust. I hurriedly dug through my clothing and threw on four more layers of clothing, gloves and a woolen cap. Our research vehicle, a 2007 Toyota Corolla, was as reluctant as I was to face the elements. The car sputtered to life, and I drove from the storage box to our research cottage on Currie Lake. A panicked search at the cottage produced most of the items I would need for a day of field observations: binocs, data sheets, life preserver, paddle, GPS.

Meanwhile, Royce, my first field assistant of the year, had arrived. After equipping him for a day in the field, and a grabbing three hours of fitful sleep, we were ready to hit the lakes this morning.

On the first day out, novelty and adrenaline keep one going. Royce and I raced from lake to lake, doing “quick-hitters” to locate pairs. In other words, we wrote down any leg bands the loons would show us readily, mapped any nests we found, and threw the canoe back on top of the car to go to the next lake. (Truth be told, we took a quick break at Dunkin Donuts for two vanilla-frosted and a chocolate creme to bolster our flagging spirits at one point.) All told we hit Soo, Flannery, Julia, Buck, Hilts, Hildebrand, Townline, Langley (the 28+ year-old female there is pictured in the photo), Squaw and Gross. Four of these pairs had nests and two others were clearly making plans. Based on this small sample, almost half of our pairs are now nesting. Considering that we have about 110 more lakes to cover, we no doubt have 50 or so nests to find in the next few weeks. Sadly many of these nests will fail quickly — before we can visit the lake — so we will never record them. In order to limit that tragic loss of data, we will continue quick-hitters until we exhaust our lake list.

This is a stressful way to start the research year, but it is also traditional. Some years, in fact, are worse, as I am unable to enlist others’ help to make a first sweep through the study area. Kristin and Linda’s first round of visits in April to locate returning and newly settled breeders spared us the trauma of having to nail everyone’s identity AND find nests. So we will endure, cheered on from time to time by a selfie — and a very occasional stop at D&D.

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The first round of censuses in the study area each year is always bittersweet. On the one hand, it is exciting to see the crop of new young adults that have settled and to wonder how well they will defend their new territories. On the other hand, some old familiar loons are missing. This year is typical in that the disappeared veterans are mostly males. Three of 12 males of 20+ years have failed to reclaim their 2015 territory; only 1 of 12 20+ females have not resettled on their territory from the year before. Thus, male senescence lives!

Among the 2016 no-shows are the Jersey City Flowage male, who bounced back from a nasty fishing entanglement in 2014, regained his territory in 2015 and hatched a chick there. Another loss is the Soo Lake male, who was among the most aggressive in our study area. I still tremble when I recall his response when we played a few loon calls in his direction in 2000. He approached my canoe to within 2 feet, sat right next to me in the stern and glowered for the better part of two minutes. A spine-tingling experience for sure!

Yet the news is not all bad. Six young ABJs (“adults banded as juveniles”) have settled in the study area, providing us with valuable data on loons whose age is known precisely. New settlers include two females hatched in Vilas County — a 9 year-old that settled on Manson and a 6 year-old now paired with the male on Harrison Flowage. New male faces belong to an 8 year-old that took over Brandy Lake (near Woodruff) and a 7 year-old that battled and evicted the 22 year-old male from Oscar Jenny. (Thanks to Jeremy, who observed this eviction in progress.)

Perhaps the most intriguing findings from the first round of lake visits by Kristin and Linda are the serendipitous ones. Kristin relocated one of our oldest males — a bird known to be 27 years of age or older. Evicted two years ago from Muskellunge Lake, this loon licked his wounds and got himself back in the game by settling on nearby Swanson Lake, which had fallen into disuse in 2015. We had not seen this bird in two years and were almost ready to give up on him. Linda found a female with even greater resiliency. This old loon produced a dozen chicks over the years as the breeder on Buck Lake from 1998 to 2009. After her eviction from Buck in 2010, she floated, found a breeding position on Hildebrand in 2012 and produced a chick there in 2013. But she was driven off of Hildebrand last year. Her response to this second setback was typical of female loons — she bided her time and claimed that territory again when the opportunity presented itself. As I confront another season of hauling canoes from lake to lake, my back begins to ache in anticipation. I hope the examples of these two dogged old codgers gives me the strength to persevere!

 

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LMG_9628 Manson Lake Male Yodeling

Loons do not settle on territories as we think they should. Traditional models in long-lived animals maintain that hopeful young individuals should be systematic in settling on territories. By current theory, a young loon should explore a certain region within proper habitat, find several territories that might be suitable for breeding, and then routinely monitor those potential breeding spots, waiting for a vacancy to occur. During this exploratory period, it is thought, the young loon gains familiarity with this small cohort of territories that will lead to a competitive advantage in territorial battles with other would-be settlers once a territorial slot opens up. The “foothold hypothesis”, as I call this model, is quite pleasing and logical. What’s more, there is evidence that many territorial animals gain territories in this manner. Loons do not.

We got another reminder of the quirky territorial settlement pattern of loons this past week, when Linda and Kristin scoured the study area and ID’d the pairs that had taken possession of the lakes we monitor. Among these settlers were many familiar faces — including a male on Townline Lake that has been in possession of the territory since 1994 and a female on West Horsehead who has bred there with a series of different males since 1995. One of the surprises was a 9 year-old female hatched on Rock Lake in Vilas County who settled on Manson, replacing a female that had bred on Manson for a dozen years. Owing to Linda’s careful observations, we know this Rock Lake female as a frequent intruder during 2014 and 2015. But she did not intrude into Manson Lake, where she eventually settled; instead she intruded repeated onto nearby Muskellunge Lake! Thus, our expectation that the Rock female was laying the groundwork for settlement on Muskellunge was not fulfilled.

There are several possible reasons why loons often do not settle on lakes that they seem to prefer. One of the most obvious is that settlement is not merely a matter of finding a desirable territory.  A loon bent on settling must also contend with the current resident on a territory where it hopes to settle. So a young nonbreeder that visits Territories A, B, and C might prefer Territory A but be prevented from settling there by a healthy and aggressive territorial resident of the same sex. In that case, the nonbreeder might end up settling on Territory B or Territory C. The Rock female is fortunate; Manson Lake, where she has settled, is one of the most productive territories in the study area. So even if she could not take possession of the territory she seemed to prefer, her future breeding prospects are bright.

You can read more about our testing of the “foothold model” for territory settlement in this blog post, which is based on a paper published in Animal Behavior. E-mail me if you would like a pdf of the paper.

The crisp photo above is by Linda Grenzer. It shows the Rock female performing a wing flap on Manson, her new breeding lake, while her mate, an 18 year-old male, yodels in the foreground.

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This past winter was a mild and relatively short one in the upper Midwest. The ice never became as thick as in most years. So the warming temperatures during the past few weeks succeeded in melting that thin blanket of ice covering our study lakes. I have gotten reports in the past few days that many of our study lakes now are mostly or completely free of ice. And the avian summer residents of those lakes are beginning to return.

LMG_8789 Clune on Territory

The first male reported back was “Clune”, seen here in Linda Grenzer’s photo from Wednesday. Playfully named by Linda after the voice-to-text feature on my iPhone butchered the word “loon” during one of our exchanges, Clune is well known to us. We first observed him as a chick on Manson Lake in 1998, found him when he settled as an adult on Deer Lake in 2003, and tracked him when he shifted to his present territory on Muskellunge Lake five years later. He and his mate have produced a whopping seven chicks since 2011 on Muskellunge — eight if you include the rehabbed chick that we released on the lake in 2014 and that Clune and Honey readily accepted and reared as their own. (Yes…Linda has named the female too!)

I am a scientist. I try to stick to the data and not be influenced by emotions and superstition and unsubstantiated inklings. Nonetheless it cheered me when Linda reported that Clune had returned very early this year and already yodeled to defend his territory from a skittish intruder who dared to enter it. Despite my better judgment, I cannot help but think that this will be a productive year for loons in northern Wisconsin.

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My mother-in-law came to visit us in California last week. She is an avid follower of my blog (!), so I was excited to learn what she thought of my most recent post. She hated it. That is, she said of my report that loons get old:”I could have told you that!”. Naturally, I was deflated. To think that 23 years in the field had produced a result deemed pedestrian by my mother-in-law!

While one might argue that she is family and should have been blindly supportive of my work, Joanne is right, in a sense. As humans, we are accustomed to old age and deterioration of the elderly. But, as I tried to explain, senescence is not the rule in all animals. Birds are unusual, in fact, as they exhibit relatively late and gradual senescence compared to mammals of similar body size. So the striking and rather sudden senescence that I reported recently is mildly surprising for the taxonomic Class Aves. Still, I think I agree with Joanne that it is not terribly shocking!

But there is more. The blog where I reported senescence in adult loons was based on an analysis that pooled male and female individuals. Since then, I have analyzed the sexes separately. The results are striking. As the figures below show, the senescence that I reported for the species as a whole (measured by decreased survival) is driven purely by males. While males and females that have been on territory from 1 to 14 years survive at a rate of 95% annually, males with 15 or more years on territory only survive at a rate of 58%. (Old females show a very modest decline in survival to about 91%.) Since males and females that settle on territories are almost always 5 years old or older, we can say with confidence that territorial males in their twenties drop like flies; females, in contrast, are survivors.

young males and females do not differ in survival rate

old males die at a much higher rate then females

I don’t know if my mother-in-law will be impressed by these data. For the moment, I must be content in the knowledge that I have found a strong and highly unusual survival pattern. As a behavioral ecologist, this stunning disparity leads to several other questions. Among them are: 1) Do older males exhibit any other evidence of deterioration such as in territory defense, chick production or body condition? and 2) Does the high mortality of older males cause the adult sex ratio to swing towards females such that females are forced to wait years before finding a mate? Rest assured that I am exploring these possibilities with great enthusiasm.

 

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I have been back in California for some months now, my research in Wisconsin a distant memory. A stroll to the end of the pier at Newport Beach changed that. Several of my study species — unbanded animals that probably belong to breeding populations from Alaska, British Columbia, or Alberta — were foraging contentedly off the pier’s end, as fishermen cast their lines all about them. The fishermen appeared to avoid casting near loons, so I was not alarmed by what I saw. Loons are usually adept at avoiding fishing lines (though not always). Furthermore, an ecologist would not be surprised to see loons sharing a fishing hole with anglers, since they are competitors for the same small fish — mostly smelt and mackerel.

Common loons were not the only species diving and pursuing small fishes among the sea lions and occasional pod of common dolphins. It was a treat to find this juvenile red-throated loon out in the waves as well.

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Back home in Irvine I am crunching data, as I do habitually in the off-season. I feel some urgency at the moment, as I am about a week away from having to give a talk on my findings at the Winter Animal Behavior Conference in Colorado.  I will be more positive in a week or so, but I have already confirmed senescence in two different respects. First territorial common loons older than 20 abruptly begin to show much higher year-to-year mortality (roughly 20% annual mortality from 20 on; only 6% mortality up to 20 years). Second, territory holders 20 and older also stand a much greater chance of losing their territory through eviction (again a 20% rate of loss) than do those younger than 20 (12% rate of loss). In the coming days I will explore whether the sexes differ in these respects and whether old territory holders make any behavioral adjustments to this apparent decline in health and fighting ability.

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Several months have passed since Gabby Jukkala’s and my article was accepted for publication in the Journal of Avian Biology. We have been anxiously tapping our feet while the wheels turn and our article comes out in the journal. This has just happened. You may now view our article here.  Gabby and I are thrilled that: 1) our article has been selected as “Editor’s Choice” for this issue of the journal, 2) Linda Grenzer’s nice photo of the female on her lake with a chick from 2015 is the cover photo for the issue (and a second is featured in the blog spot), and 3) the journal has included extra information about us and our article on their website here.

I have already described the findings we report in the article, so I will not rehash those here, but do take a look at the article, which the journal is making available free of charge, since it is “Editor’s Choice”. It is a very small honor, in fact. Still, these days I am often on the Newport Pier, as that is a good local birding spot and I must prepare for the Ornithology class I am teaching this fall. Whenever a member of my study species wanders nearby, as it forages for mackerel or smelt, I find myself smiling a bit more strongly than before.