Since I am trying to turn the corner after yesterday’s disaster, I am happy to announce that Gabby Jukkula’s and my paper is now available. The editor at Journal of Avian Biology seemed pleased with the article; he asked me to produce a short blog post for their website, which I did. It describes the genesis of the article, the preeminence of male parents in defense of loon chicks, and a rare case in which a male parent died when his chick was less than a week old and his mate beat the odds to rear the chick to adulthood without him. Perhaps the glow of having the article and blog come out will cheer me up!
Many of you are not in a position to help, but to those folks who live in or near our study area: we are in a bind.
We had a mishap this morning with the Chapman vehicle that we use for both making behavioral observations and — more important — for towing the boat we use to catch and band our birds. With less than two weeks before the capture season begins, we are without a vehicle to do the work.
If anyone knows of a reliable, used vehicle that we can purchase or rent and that can be fitted with a trailer hitch, we would love to hear about it. We will probably figure out some way to solve this problem on our own, if no one can help, but we would appreciate any help you could give us.
Feel free to call me at 949-751-9015 or e-mail me at email@example.com.
On 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.
After 2014’s disastrously low chick production owing to black fly infestation, I was anxious that breeding success would rebound in 2015. My concern defied reason. Loons are long-lived, of course, and a few or even several consecutive years of below-average chick production are not enough to have a lasting negative impact on the population. Still, blinded by the irrational human tendency to infer long-term impacts from short-term patterns, I wished to see our loon pairs come back and raise many chicks in 2015, just as Linda Grenzer’s pair has (see photo).
This year is shaping up to be a very good year indeed. As of this date, 31 of the 120 territories we follow (25.8%) have already hatched chicks. In contrast, only 2 breeding pairs (of 112 pairs; 1.8%) had chicks on this date in 2014. That is an unfair comparison, because the black flies devastated early nests in 2014. However, 2013 was a rather good year for chick production, and in 2013 only 20 of 108 pairs we followed (18.5%) had chicks on this date. Although these data are slightly biased because of yearly differences in nesting schedules — that is, 2013 was a slightly later year than this year — 2015 should be an awfully productive breeding season for loons in northern Wisconsin. As a scientist, I am breathing a huge, sheepish sigh of relief!
The Loon Project counts on efficient exchange of information with lake residents and loon enthusiasts as a means to acquire good scientific data. We cover enough lakes — about 120 this year — so that we make visits to them only once every 5 to 7 days. This permits us to track the identity of the breeding pair and record their breeding activity. Over time, we accumulate important data on territorial fidelity, eviction of breeders, and their relocation to other study lakes. But weekly hourlong visits leave lots of holes in our knowledge. So it is helpful that almost all of our lakes are occupied by humans who take an interest in “their loons” and contact us or the Wisconsin Department of Natural Resources when something is amiss.
Yesterday, a resident on Flannery Lake called with distressing news. The male on the lake, a 14 year-old reared on Washburn Lake, was dead and being fed upon by a mink. We were particularly saddened to hear such a report from Flannery, because the breeding pair had attempted to rear young every year there since we began to follow them in 1993, but had not fledged a chick successfully since 2006. That unlucky string seemed about to be broken when, earlier this month, the pair hatched two vigorous chicks. We were delighted, though perhaps less so than lake residents, who had watched their loon pair build nests, lay eggs, and incubate them diligently year after year only to lose them — or their small chicks — for reasons unknown.
This morning Seth visited the lake to see whether the female and chicks were still alive and whether another male had taken the deceased male’s place. He snapped the photo above, showing that the female, who is at least a quarter of a century old, is alive and well, as are both chicks. However, he also reported that a possible incipient pair was present on the lake. This makes sense. As I have noted in recent posts, male loons use their yodels to keep hopeful settlers at bay. With no male present to yodel, intruders flying overhead readily land in the lake. Since the female cannot safely leave the two-week-old chicks alone, she cannot easily engage intruders and drive them off. In short, Flannery is prone to intrusion and settlement.
Despite the difficulty of her situation, Seth reports that the Flannery female continued to show territorial behavior towards intruders this morning. It remains to be seen whether she can find refuge on the lake such that she can both avoid any new pair that settles and forage to sustain herself and her young chicks. It is a tall order. Indeed, we have only once observed a female whose mate died or was evicted raise a young chick on her own. In 2012, the male on Squash Lake died of lead poisoning owing to an ingested sinker, leaving his mate and a chick only a few days old. The Squash female that summer miraculously succeeded both in rearing the chick to fledging and in pairing with a new male — a lesson to us all that child-rearing need not prevent an active social life. “Miracle Chick”, as we came to call the survivor on Squash, became our most revered juvenile that year. (Miracle Chick is pictured below with Kristin and Gabby.)
So there is reason for hope for the young Flannery chicks. If she is vigilant and fortunate, a female can raise a chick, perhaps even two, without help from a male. Considering the long odds of such an achievement, we should certainly resist optimism at this point. We will keep an eye on this fractured family, and I will let you know how things turn out.
In his routine visit to Two Sisters Lake to check on the status of an incubating pair, Chris was alarmed to find out that the male had a hook lodged in his cheek and fishing line protruding from his bill. This male — captured and marked in 2010 as a breeder on Brown Lake before being evicted two years later — had been a “floater” for the past three years before replacing the absent Two Sisters male this spring. I was thrilled to see this tame bird get his life back together.
When Chris reported the hook in this male’s bill, I wondered if this bird was just snakebit. The entanglement could not have occurred at a worse time. The male and his mate were on the brink of completing four weeks of incubation and hatching of two chicks, which require great care and protection at this stage. Indeed, between yesterday morning and afternoon, the male had finished incubating the second egg and left the nest for good with two head-sized chicks alternately hiding under his wing and riding on his back. Attentive as he was, the hooked male was ill-equipped to defend his brood. As we have learned recently, male loons are especially vital to the defense of a pair’s young chicks, because the male-only yodel discourages landing by intruders (which, on occasion, kill young chicks) and because males are active defenders of chicks towards intruders that approach them in the water. With the hook lodged in his mouth, the male was unable to open his bill, and his protective vocalizations yesterday were so muffled and distorted as to be ineffective.
Upon receiving the report of the hooked male yesterday, we agonized over the decision of how to proceed. Adults with small chicks are the easiest to capture, so we were not worried about catching the male. However, one must take great care when young chicks are present, as they are tiny and are always on, next to, or underneath the wings of the adults. When one is netting the 10 to 12 pound parent and hauling it into the boat, it is conceivable that an unseen chick might be crushed beneath it. Would it be wise to wait for a few days or a week, until the chicks were larger and stronger, before attempting capture? In the end, we decided that the male was impacted enough that we were endangering his life and those of the chicks if we did not act immediately to help him. So last night, Joel, Eric and Seth set out on Two Sisters to try to: 1) gently separate the tiny chicks from the male, and 2) catch the male so that the hook could be safely removed by Mark Naniot of Wild Instincts, who was standing by on shore.
As you can see from Seth’s photo, we caught the male, and Mark expertly removed the hook from his cheek. The chicks were unharmed in the process. The male seemed in good shape, considering his close encounter with an angler’s line. (We suppose that he became hooked only a day or so before we caught him.) Still, we shall be checking today to see that the family is back to normal. While there are many dangers facing loons in the first few weeks after hatching, the team of rehabbers and loon researchers has given them a chance to confront these dangers without human impacts layered on top!
Two mornings ago, I saw my very first chick of the year on Woodcock Lake. My visit to Woodcock was memorable — not just for that reason, nor because of the rarity with which the loon pair there hatches a chick. Rather, I chanced to witness with great clarity one strategy that adult loons employ to defend their offspring. It is moments of this kind, when loons’ behaviors and motivations become visible suddenly and starkly, that fuel much of my thinking and writing about the species.
If you have read my recent posts, you know that we have learned a good deal about how loons defend their young from opportunistic intruders, which on occasion find and kill chicks less than two weeks old. We know that males possess a acoustic tool that females do not — the yodel — which conveys aggressive motivation and therefore can be used to discourage intruders within earshot of the territory from landing there and imperiling the chicks. What was less clear was whether males yodeled at a high rate as a generalized strategy to inform would-be intruders that visits to the yodeler’s territory would likely provoke an attack or whether, instead, yodels were targeted at specific intruders as they passed over a territory or began to land there.
On Saturday morning I arrived at Woodcock to find the male with a tiny chick riding on his back. The female was on the nest 200 meters away, incubating the second egg, which by now might have produced a second chick. As the sun rose above the horizon that day, intruders criss-crossed the airspace above the territory. Two such “flyovers” were especially enlightening. At 535, two intruders began to descend as they crossed the lake, preparing to land next to the male, near the lake’s center. The male crouched down, dumping the chick into the water, and uncorked a deafening yodel at just this moment. In response, the two flyers checked their glide down towards the lake, flapped rapidly to regain lost altitude, and flew off to try their luck elsewhere. Seventeen minutes later, this pattern was repeated. This time a lone flyer crossed just above my canoe, descended to within three meters of the lake surface — the whistling of wind across its wings easily audible in the morning stillness — before hearing the male’s acoustic objection and beating its wings desperately to abort the landing and ascend.
Though we had statistical evidence to suggest that male loons used yodels to repel specific intruders, I had never observed as clearly the effective targeting of flying intruders by a yodeling male. While songbirds sing incessantly during the spring in nonspecific fashion — that is, they sing repeatedly over hours, days and weeks to communicate their readiness to mate to any female in the vicinity and/or their willingness to defend their territory to any male that happens to be nearby — male loons seem to use yodels with surgical precision. In other words, loon males yodel rarely, and when they do, they aim their yodel at a specific target with a specific goal in mind.
Why are male loons so stingy with their yodels? Two possibilities come to mind. First, yodels appear to have a relatively high metabolic cost compared to songs of other animals. Perhaps, then, mere energy conservation places a limit on the frequency of this call. Second, Jay Mager’s work has shown that males reveal both their physical size and their physical condition when they yodel. By yodeling, therefore, a male might convey information about himself that he would prefer to keep private. Of course, a large male in good physical condition should be more apt to yodel, one might argue, whereas a small, ailing male should keep his bill shut so as to avoid an eviction attempt by a rival passing overhead.
I look forward to testing the prediction that male loons yodel rarely — and vary systematically from one to another in their tendency to emit the vocalization — as a means to avoid sharing information about themselves. That is a clear, well-grounded prediction that might produce an important finding. But my morning on Woodcock reminded me of a great benefit that I earn from spending time in the field observing loons. One can spend countless hours entering data and churning through statistical analyses to reach a rock-solid conclusion about animal behavior (and I do). But the occasional “Eureka” moment spent with animals in the field is invaluable.
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.
We have almost completed the first round of visits to study lakes. Our ever-expanding list of lakes makes this no mean task, as our list has grown from 95 territories in 2008 to 123 this year. Kudos to the field staff of Joel, Eric, Chris, and Linda (whose photo appears above), who have worked hard to visit lakes and ID loons from leg bands — and also Al on West Horsehead and Pat on Silver Lake, who have e-mailed with data from their lakes.
Of 162 banded loons on territories as of late 2014, 141 (or 87%) have reclaimed those territories this spring. Among 21 missing territory holders from 2014, 4 have been resighted in 2015, but were apparently evicted from their territories early this year. Thus, the minimum survival rate from 2014 to 2015 for territory holders is about 90%. This figure agrees closely with survival rates calculated from Wisconsin and elsewhere within the breeding range.
Sky-high return and survival rates for our population highlight a simple pattern in the life history of common loons. In ecological terms, loons are “K-selected”. That is, they are long-lived, take several years to reach sexual maturity, produce few offspring during their lives, and invest heavily in parental care for the few offspring they do produce. Loons are not explosive reproducers that “shot-gun” many offspring out into an uncaring environment in hopes that a few survive. Rather, they work hard to maintain ownership of their breeding territory, eke out one or two chicks a year (in a good year!), and defend their chicks vigorously against all comers!
Sorry to trouble you with posts on back to back days, but we just got good news from the Journal of Avian Biology. A paper by Gabby Jukkala and me that describes chick defense of loon parents towards decoys has just been granted final acceptance. We are delighted, because we have forged our way through numerous revisions of this paper over the past year or so. It is nice to see that our labors were not in vain.
In fact, the struggle to get this manuscript published is a good illustration of how peer review can lead to new perspectives and discoveries. The paper quantifies the defensive responses of parents to a decoy of an adult intruder; intruders attack and sometimes even kill small chicks. Gabby and I had been able to document that parents of small chicks (0 to 2 weeks) remain near them when a decoy is placed nearby (apparently to ward off surprise underwater attacks), whereas parents of older chicks (4 weeks+) confront the artificial intruder. But in response to reviewer comments, we sharpened our analyses and discovered two more behavioral patterns. While we had long known that males are especially apt to yodel when they have small chicks, we learned through this improved analysis that males with TWO chicks are four times as likely to yodel as males defending a SINGLE chick. This find suggests that males increase parental care in response to the value of the chicks. In addition, we noted that males are more than twice as likely to penguin dance in defense of their chicks as females.
In short, our new paper clarifies our picture of chick defense in loons. Males shoulder a disproportionate share of the burden for chick defense, as we document. Males spend far more time with chicks than do females, yodel at intruders (which females cannot do), and penguin dance much more often than females do. Moreover, male behavior is not mindless, all-out aggression. Indeed, it is nuanced, as males’ toughness towards intruders is combined with a cold calculation of how they can best maximize their Darwinian fitness.