LMG_2782 Muskellunge Chicks Hide from Intruders

Linda Grenzer’s striking photo from two weeks ago got me thinking about loon breeding success. The picture is a sight that will please loon fanciers — two big healthy 9-week-olds resting side by side while their parents circle with intruders. (The chicks are holding their legs out of water, as resting loons commonly do.) Since territorial pairs almost never lay more than two eggs or hatch more than two young, the photo depicts a monster year for the breeders on Muskellunge Lake. Despite black flies and raccoons (which threaten nests), eagles, muskies and snapping turtles (which attack chicks), and constant intrusions by competing adults (which seek to drive adult breeders off of their lakes), the male and female on this lake reared two chicks to adulthood. Quite an achievement!

For Muskellunge, 2016 marks the sixth year in a row of chick production. Ten chicks in all have been raised by the pair during this stretch (including one rehabbed chick we added to their singleton brood in 2014). While I am thrilled to see such an abundance of chicks come from a single lake, it is not the norm. As residents on most lakes well know, loon breeding is a dicey proposition.

Consider, for example, South Two Lake, a normally productive breeding lake where the sudden disappearance of two successful breeders after 2015 left the lake wholly without a pair in May and June of this year, until it was finally resettled by a male and female in July — far too late for nesting. Or look at the Boom Lake-Hodag Park territory, where the pair had fledged five chicks across the past four seasons until the male became entangled in fishing line in the spring of 2016 near Panama City, Florida and never reached Wisconsin. Baker Lake was a consistent chick producer until 2013, when a five year-old male settled there with an unmarked female; they have lost nests to predators each year since then. Most spectacularly, the productive pair on Blue Lake-Southeast weathered the storm of parasites, egg robbers and chick predators only to see the male lose territorial ownership to a young usurper, which resulted in the chick’s death. Finally, pity the pair on tiny Liege Lake or Wind Pudding-West where, despite successful territory defense and incubation, the parents were unable to locate enough food to raise a single chick past six weeks of age.

In light of the many hazards facing loon pairs, it seems remarkable that we ever see a photo such as the one above. As one might surmise from the preceding paragraphs, there are several requirements for successful breeding. Abundant food is essential, of course. Each year, many pairs attempt to breed on tiny lakes where food limitation prevents them from rearing even a single chick, let alone two. Nesting habitat is vital; lack of boggy or marshy shoreline or an island prevents many pairs from even attempting to breed. Two less obvious factors can make or break a breeding effort: 1) the ability of both pair members to maintain their breeding positions throughout the season despite an onslaught of young adults looking to evict them, and 2) the male’s familiarity with proven successful nest sites, which dictates whether the nest is positioned in a location likely to survive four weeks of incubation.

Some breeding pairs have everything going for them, so that they surmount all obstacles and raise chicks to fledging year after year. Muskellunge (see photo) is large enough — at 160 acres — that food abounds, and the lake features several shoreline zones that support nesting. The resident female is much larger than average and aggressively repels intruders that challenge her. She is paired with a tough 18 year-old male — a bird experienced enough to know the locations of multiple nest sites on the lake but young enough to be in good physical condition and not vulnerable to eviction. In short, Muskellunge Lake is currently in a “sweet spot” for raising chicks, like Townline, Manson, Little Bearskin, East Horsehead, and Buck Lake. Lakes that get on a roll like these produce a disproportionate number of chicks, which will mature, return, and sustain the population. In time, these productive territories will falter, owing chiefly to the loss of one or both members of the vigorous, experienced breeding pair. For now, though, let’s enjoy the bounty of offspring that these lakes produce and look forward to the emergence of new productive territories that will succeed them.

 

If you have been floundering lately, as I have, let’s gain some perspective by considering the plight of the Silver Lake loons. The pair’s struggles began in mid-May, as black flies thwarted their efforts at incubating a first clutch of eggs. According to Pat Schmidt, who watches the pair carefully throughout the breeding season, incubation proceeded normally during the nighttime — cool temperatures kept the relentless pests at bay. But the marked female and male were unable to stay on the eggs during daylight hours, when black flies were active and biting. On again, off again incubation finally gave way to abandonment during the last week of May, but the pair reset themselves quickly, adding two additional eggs to the two they had earlier tried and failed to hatch. Despite the cumbersome task of warming four large eggs simultaneously, the birds produced a chick at the very end of June. Their fortunes seemed to have turned.

The greatest risk faced by a breeding loon pair with a chick is our national bird. Bald eagles nest on tall white pines along lake shores and are a frequent sight over lakes. Indeed, eagles are such a routine part of the scenery on the lakes that loons often deign to wail at them as they pass overhead. Eagle fanciers might try to convince us that these raptors even purposely lull loons into a false sense of security with their constant, mostly innocuous flights nearby so that they can occasionally strike at loons suddenly with deadly purpose. An opportunity for such a surprise attack might occur when an eagle appears just above the tall trees at the lake’s edge as a week-old chick’s parents both happen to be underwater diving for food. Perhaps it was such happenstance that allowed an eagle to carry off the Silver Lake chick on July 2nd. In any event, eagle predation brought the breeding efforts of the pair to an unsuccessful close this year.

The sting felt by lake residents at the loss of the chick had begun to abate by July 18, at which point the territorial female, “Copper” (named for one of her plastic leg bands), found herself in a desperate battle. She was beaten badly, chased across the water, attacked from below as she rested on the lake surface, and finally forced to take refuge on land to escape further damage. By the time the violence had ceased, Copper had to be carried, helpless, to the Northwoods Wildlife Center. She died there a few days later.

As I have made clear in numerous posts, males are the ones that battle dangerously (apparently because of senescence) in most cases. So how do we explain the latest Silver debacle? An oddity concerning contestants might offer a clue in this case. Copper, who had reared chicks on Silver in 2014 and 2015, had battled repeatedly for ownership over the past several years with her bitter rival, “Mint”, the previous Silver female and mother of the chicks in 2010 and 2012. Even after losing the territory to Copper in early 2013, Mint was a frequent intruder into Silver Lake. Hence, both females had raised chicks in multiple years with the male, and both were highly motivated to vie for control of the territory. In addition, banding records indicate that Copper and Mint were of very similar size.

Now to game theory. If an animal encounters a long-lived opponent with which it is very closely matched in fighting ability but happens to get the upper hand at some point, it might then pay for that first animal to press its advantage and even kill the opponent. Why? Because our research has shown us that closely-matched pairs of females, like Copper and Mint, often give each other fits. Two females on Heiress and two others on Oscar-Jenny were so close in fighting ability that they traded off ownership of those territories over many years, each female hindered in her breeding efforts because of the constant interruptions of the other. The result was poor reproductive success for both rivals. Although there is enormous risk involved, it might occasionally pay for females to exhibit the vicious battling we associate with males. Specifically, a lightning strike to finish off your archrival might sometimes be worthwhile to avoid a chronic, destructive feud.

 

_IMG7567

With Mother’s and Father’s days still fresh in mind, maybe this is an apt occasion to relate a quirky instance of parenting in loons. The topic came up abruptly last week, when Doug Giles, a lake resident in British Columbia, sent these photos. At first, I could not even

_IMG0771 fathom what species of duckling was receiving this unanticipated caregiving. A frantic web search of ducks breeding in the vicinity revealed that this is a young Common Goldeneye. But how could such a duckling escape the watchful eye of its own mother and blunder into the path of a pair of loons?

The curious breeding behavior of goldeneye ducks provides a clue. Goldeneyes lay 7 to 10 eggs in tree cavities, and the female is the sole incubator. (Male goldeneyes leave the picture shortly after incubation begins and play no role in rearing offspring.) Goldeneye ducklings follow their mother away from the nest a few days after hatching. Unlike loons, goldeneye young feed themselves; their mother merely protects them and guides them to feeding areas where they are relatively safe from predators. The task of herding ten or so ducklings about creates logistic hurdles; ducklings commonly fall behind or lose track of their mother and siblings. When goldeneye hens converge in the process of guiding their respective broods, young intermingle, creating creches of dozens of ducklings of varying parentage. Finally, female goldeneyes, especially those with small broods, often abandon them — leaving the ducklings to fend for themselves or coalesce with broods where the female is still present.

_IMG0793.jpeg

 

In short, rearing of massive goldeneye broods seems haphazard and impersonal when compared with the parental behavior of common loons. If common loons are modern-day human parents in the era of small families, abundant participation awards, and kindergarten SAT prep; goldeneyes are the all-out reproducers of the pioneer days, never quite certain of how many young they have and where they all are! So we should not be surprised to encounter a misplaced or forgotten goldeneye duckling.

But why would loons adopt a young animal that differs markedly from a loon chick? First, it is important to understand that loons — like many animals — are hormonally primed to care for young. That is, young production is the crucial measure of evolutionary fitness, so we should expect all species to be committed to the rearing of young, if parental care is obligatory for survival in that species. Apparently, the drive to provide parental care is sufficiently strong that it can get misdirected at times. Among all ducks that loons might adopt, goldeneye are a good match, as they are diving ducks (not dabblers, like mallards) and subsist mainly on aquatic invertebrates and occasional small fish. Clearly this duckling is developing more of a taste for fish than is usual for its species, as Doug Giles’ first photo shows. The duckling’s willingness to accept food from another individual, moreover, shows impressive flexibility in behavior that we might not have expected.

While we can understand how the adoption of a goldeneye by loons is plausible, it is still a remarkable event. The likeliest outcome of a close brush between a small duckling and a loon pair is an attack; many ducklings are killed by loons each year. Perhaps this loon pair was primed for adoption by having lost their second chick shortly before they encountered the stray duckling.

One factor to which we definitely cannot attribute the successful adoption is relatedness between ducks and loons. Ornithologists have long known that ducks and geese are not closely related to loons. In fact, goldeneyes are cousins of turkeys and chickens, while loons are in the evolutionary lineage that includes herons, cormorants and penguins. The superficial similarity in appearance between loons and ducks results from evolutionary convergence, not common ancestry. In my view, the distant relationship between loons and goldeneyes is yet one more reason to marvel at the odd parent-offspring bond that has formed here — and hope that it leads to a good outcome.

 

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 their 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.

 

 

2016-05-20 16.48.46

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.

 

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.

2016-05-15 12.48.07

LMG_7851 Walter n Sammy

The season began inauspiciously at Crystal Lake in Lincoln County, which is along the southwestern fringe of our study area. Though it is a pleasant, rather clear lake, Crystal offers no nesting habitat for loons. Loons love most of all to place their nests on islands but also make use of boggy or marshy areas, which seem to provide safe havens from egg predators like raccoons and skunks. Crystal offers none of these options, as its shoreline comprises upland habitat and is thus easy for a hungry mammal to patrol. In fact, Crystal is such an inhospitable place for loons to breed that loon eggs vanish from its shoreline almost as soon as they are laid.

So I had mixed feelings to see a six year-old male hatched on nearby Muskellunge Lake settle to breed on Crystal in 2012. On the one hand, I was pleased that the young bird had found a territory after wandering around the local neighborhood of lakes for the three previous years. On the other hand, a settler on Crystal seemed doomed to reproductive failure. But the male and his parade of mates (three females in five years) persisted in their breeding efforts. As I reported earlier this summer, the male and his new mate in 2015 (she still licking her wounds from a recent eviction from neighboring Deer Lake) took a new approach to nesting in 2015 by choosing to place a nest on a swim raft off of a resident’s dock.

LMG_6672 dad n chick on raft

Once the egg had been protected from rolling off of the raft with a ring of rubber cut from an old tire and some natural nesting vegetation (thanks to quick thinking and skillful craftsmanship from Linda and Kevin Grenzer), things began looking up for the breeding pair. Although it was a bear for the male and female to clamber up onto the swim raft to incubate the egg, the setup seemed little different from the artificial nesting platforms that many lake residents place on the lake each year for their nesting pair to use. Given the virtually impregnable location, the probability of hatching a chick had gone from almost zero to near one.

As expected, the chick hatched successfully, and though it had trouble maneuvering around the rubber-reinforced nest (as Linda’s photo shows, above), it left the nest with its parents within a few days. Only when Linda reported that Crystal was experiencing a burst of territorial intruders — one of whom, by chance, was the mother of the Crystal male and hence the grandmother of the chick — did she and I become panicked. Intruders pose a grave hazard to small chicks. Would the pair that had so miraculously pulled off a hatch turn around and lose the chick to an infanticidal visitor? The threat was not trivial. As Linda’s remarkable and chilling photo shows, the Crystal parents broke a very basic rule of loon parenting: never permit intruders near your chick when it is less than 2 weeks old.

LMG_6709 Two intruders approach parent n chick2

Yet the chick survived this brush with death. Nourished by a healthy supply of fish from the lake, the chick grew so rapidly that we were able to band it at three weeks of age, much younger than is usually possible for loon chicks. It has continued to flourish since capture. Now, at roughly 8 weeks of age, it looks like a 10-week-old, as the opening photo attests.

I have a tendency to dwell on disasters. Confronted with a large set of events — some positive, some negative — the latter seem to stick with me longer, leaving me with a sense that things are not going well at present and might not go well in the future. Yet at the end of a season when many breeding loons flirted with disaster — and one died — the story of the plucky Crystal chick stands as an odd and memorable exception.

LMG_5401 Crystal Lake NestOn its face, the photo is comical. A loon sits on its egg on a swim raft, a meter from an American flag. A garish McMansion is visible on the opposite shore. Few photos of the common loon are more at odds with the image of the species as a symbol of the northern wilderness. Yet Linda Grenzer’s photo of the nest on Crystal Lake is a poignant portrait of the situation faced by most territorial pairs in north-central Wisconsin.

Many popular accounts describe common loon populations as holding on for dear life. To be sure, loons are threatened by shoreline development, which reduces nesting habitat. Recreational fishing and boating kills many adults and chicks prematurely each year. And methylmercury in the food chain, swollen by coal-based power production, likely impacts the loon population as well.

Against all odds, however, loons appear to be holding their own in northern Wisconsin. Despite consistent losses caused by collisions with boats and entanglement in fishing lines, populations have bounced back in recent decades. The surprising resilience of loons seems to result from two facts. First, loons prefer to nest on small islands and on boggy and marshy habitats that humans avoid. Thus, loon pairs continue to produce young on lakes that are virtually encircled by human dwellings. Second, as illustrated in the photo, loons tolerate — and rarely even benefit from — human alterations of aquatic habitats.

The pair on Crystal Lake, whose nest is pictured, were in a real bind. Crystal is a very pleasant lake, but it lacks islands — the nesting spots most favored by loons — and also features neither bog nor marsh. Previous nesting attempts by the male (reared on nearby Muskellunge Lake in 2006) and a parade of 3 or more different females since 2011 ended in abject failure, the eggs an annual donation to local raccoons. Although they crawl onto it with great difficulty and complete loss of dignity, the Crystal pair decided a few weeks ago to place their nest on a low-lying swim raft. The raft is high above lake level and not equipped with any sort of ramp to assist small chicks in re-mounting the raft once they have entered the water, so we are concerned that the chicks will not be able to return to the nest (to be kept warm by a parent in the first few days of life) once they have left it. Still, the likelihood of hatch is good, and Linda and her helpers placed nesting material on the raft to keep the eggs from rolling off. We are hopeful that the loons can cope with the problem of nest height just as they do with a host of other anthropogenic obstacles each day in northern Wisconsin.

I shall keep you informed. If the Crystal pair can hatch and rear their chick to adulthood, they will be a vivid example of the capacity of loons to adapt and thrive in an environment thoroughly dominated by another species.

LMG_4598 Feeding chick on nest

It was actually yesterday when Linda reported that her much-loved and -studied loon pair had hatched two chicks. May chicks are a very good sign! Even a better sign: 75 of 119 territories we observe are on nests, and only 8-10 pairs abandoned their first breeding attempts owing to black fly infestation. In short, we are off to a good start and hope for a bumper crop of chicks in 2015.

Linda’s stunning photo illustrates the exceptional efforts that loon parents make to care for their chicks. In the photo, the female offers a tiny minnow to one hatchling, while the male looks on, and the second hatchling scampers about the nest. In the coming weeks, the pair will offer steadily larger fish to their young. Both pair members — but especially the male — will guard the chicks closely. The male will yodel at any intruders that fly over or land in the territory. He will be particularly vocal this year, because he has two chicks, not just one. The female too will attend the chicks closely when they are young, but she will start to wander off a bit after they reach four weeks of age, leaving her family to forage apart within the territory and even visiting neighboring lakes.

Why do females seem to sherk their parental responsibilities, forcing their mates to take up the slack? We do not know. We suspect, however, that females desert their families and fly off to nearby lakes to draw attention away from their own lake and chicks. You see, intruders are attracted to adults in the water; the more adult loons they see on the water, the more likely intruders are to land. So females with chicks further two goals by “decoying” intruders away from their own lakes. First, they protect their chicks from intruders, which sometimes attack and even kill them. Second decamping females protect their own breeding position on the lake by reducing the likelihood that intruders will find their chicks and target the lake for takeover attempts the following year.