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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.

black fly

Black flies have a terrible beauty. From a distance, they are merely pests, which we must tolerate for a few weeks each year. Up close, they are carefully crafted machines with specialized sensory capabilities and sharp tools sculpted to pierce the skin of mammals and birds and extract the blood they require to nourish their eggs. You have to respect them from the standpoint of evolutionary design.

Yet I spend little time admiring these creatures. Indeed, I dread the two-week period in early May when adult female black flies (Simulium annulus) emerge in vast numbers and descend upon loons. Black flies render each day a trial for loons, which are trying to locate nest sites, mate, build nests and prepare themselves for four weeks of joint incubation. Hounded by flies throughout daylight hours when they are above water, loons drop their normal routine and begin to dive incessantly to minimize blood lost to the flies. Breeding pairs that have completed nests and laid eggs are often forced to abandon efforts to incubate them owing to the relentless insects.

In the past several days, fly populations have spiked, and loon pairs are now suspending their breeding efforts for the moment and simply ditching the flies. We hope that loons’ nesting efforts are not so closely synchronized with fly emergence this year as they were last, when black flies reduced loon breeding success dramatically. If this is a typical year, a small percentage of loon pairs (say, 10-20%) will abandon their eggs on account of the flies, but many more pairs will persevere in spite of the pests. So our hopes for a banner year of chick production are, as yet, intact.

Although their travails pale in comparison to what loons face, even loon researchers are impacted by black flies. Eric, Joel, and Chris are in the final stages of covering the study lakes for the first time. Since they are trying to observe leg bands of loons that are diving constantly to avoid flies, the LP team will confront a steep challenge in the next few weeks. I hope they are up to it!

LMG_3148 SOO ABJ It is easy for me to say, I suppose, because I am sitting here in southern California in my shorts and t-shirt, wondering only if we have enough lemonade to survive the day (and enough water to make lemonade)! Still, I think most of us can agree that the season is beginning to turn. This week’s highs in Oneida County will be in the 60s, which should take care of most or all of the remaining ice on the lakes, especially with the help of the wind. After a rather brutal winter, we have an ice-out that is about a week earlier than average. Early iceout created an odd spectacle on many lakes this week past: open water devoid of loons. To be sure, breeding pairs are trickling back. Joel Flory has confirmed that both members of the breeding pair on Manson Lake have returned. Lake residents have spotted a pair on Lake Mildred and one of two pair members on Sherry. Linda Grenzer reports that “Clune”, the male on Muskellunge Lake, returned on Friday for the first time, although his long-time mate, “Honey”, has not shown up, and he is currently frolicking with a new female (see Linda’s photo, above) that we banded as a chick in 2004 on Soo Lake, Linda reports. (We are not judging!) Why would territory owners leave their lakes undefended, especially at a time when many adult loons without territories are on the prowl, anxious to seize any vacant lake? The answer is simple. Weather changes rapidly. As migrants that must fly hundreds of miles between the wintering and breeding grounds, loons face a meteorological puzzle. If they molt their feathers and migrate too early to the breeding grounds, they will encounter wintry conditions and uninhabitable frozen lakes on arrival, struggle to find enough food on open water along rivers, and ultimately settle on their breeding lake in poor condition. They will then be at risk for losing their territory to a fitter, stronger usurper who times his or her arrival better and remains in better condition. If, on the other hand, they wait too long to migrate, they might return to find a squatter established on their territory. In such cases, a territory owner would have to battle the squatter to reassert itself as owner. In short, gauging when to return to the lake you own is an inexact business for a territorial loon. We can understand why they might often arrive a bit too early or too late. So we must be sympathetic about the pitfalls of long-term planning and content with a steady trickle of returning loons. Don’t worry. Territorial loons have evolved a sound set of strategies for coping with fluctuating weather conditions — and interlopers. We expect to see most of them re-established on territories within a week. I will keep you posted!

LMG_2826 Three Month Old Chick Wing Span

I just got a report from Kristin, who is still in the study area. The chick hatched and reared on little Buck Lake popped over to Crescent Lake for a visit. Kristin was excited, because she had seen many cases of juveniles flapping their wings and practicing takeoffs, but this was the first flight of a juvenile she had recorded to a nearby lake. Thus begins the phase of juvenile wandering that characterizes the fall months. If this year proves typical, trips of maturing juveniles to neighboring lakes — sometimes up to 10-15 miles from their natal lake — will abound in the next 9 to 10 weeks.

But why do juveniles abandon the comforts and familiarity of their home lake to venture to lakes unknown? This is a difficult question with many possible answers. First, let’s think about the downside of such movements. In deserting its natal lake, a juvenile will be faced with new food sources to which it will have to adjust. Since it must feed itself and mature rapidly to put on weight for fall migration, leaving home seems a gamble. A new lake will also contain new risks in the form of predators or aggressive territory holders (although aggression is generally low in the fall, to be sure).

In order for wandering to new lakes to be a sound behavioral strategy, we would expect there to be advantages that more than offset these risks. One can imagine a number of potential benefits to shifting to a new lake. In the case of the Buck juvenile observed by Kristin, the bird was moving from a small lake with limited food resources to a much larger lake with a more abundant prey base. So the short-term benefit of being able to capture more food and put on weight for migration might be a large part of the explanation. Catching and consuming new food items might pay benefits down the road for young loons, as well, as this forces them to practice new modes of foraging that might be useful during migration and winter, when they will be faced with vastly different prey.

LMG_2823 Three Month Old Chick

There is a third and more nebulous hypothesis that might explain wandering by juveniles in fall. Three to four month-old individuals might be laying the groundwork for their lives as adults by exposing themselves to many different lakes and learning which are most suitable for them. That is, juveniles might try out lakes of different sizes and shapes containing different fish and invertebrates as a means of finding out what sort of lake allows them to feed most efficiently. If so, this period of exploration might allow them to target lakes more effectively when they return to northern Wisconsin (as they do) to look for a breeding territory in 2 to 5 years. It is even possible that young loons — especially males, which often settle to breed within a few short miles of their natal lake — move from lake to lake in order to create an internal map of the local area, which they will use in a few years when they return in adult plumage and seek a breeding territory.

Like many behavioral hypotheses concerning free-living animals, these 4 hypotheses for fall wandering are vexing to test. But they are not wholly untestable. For example, if juveniles simply move for better foraging, those that move should have higher masses in the fall than those that remain on their natal lakes. And if shifting between lakes prepares juveniles for foraging during migration and winter, frequent-shifting juveniles should enjoy higher survival than infrequent shifters. Even the hypothesis that juveniles begin to map out the local area for their later use can be tested to a degree, as it predicts more rapid settlement by frequent lake-shifters than infrequent ones. So we may, in time, begin to understand juvenile shifting. (This will come as a great relief to Kristin, no doubt, as she is braving the cool, rainy weather to document lake shifts by juveniles that we banded in July and early August.)

As I have noted before, the more immediate reason for tracking local movements of young juveniles has to do with learning about the development of natal-site matching behavior that we found recently. (Natal-site matching refers to the striking tendency of young loons to settle as adults on lakes that are similar in size and water chemistry to their natal lake.) We are curious to see whether loons show preferences for natal-like lakes even in their juvenile movements. If so, short trips during the fall to natal-like lakes will, of course, reinforce natal-site matching and yield young adults that have very strong natal preferences indeed!

Thanks, as so many times before, to Linda Grenzer, who provided these nice shots of the 2014 chicks on her lake. Although it is bittersweet for her, Linda hopes that these two juvies will soon themselves fly off to nearby lakes to gain valuable experience — or maybe just weight — that will prepare them for migration and beyond.

 

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.

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.

In most cases, loons die when they are hooked by fishing lures or snarled in monofilament line. Cases in which birds are able to free themselves and recover — or we catch them, nurse them back to health, and they put their lives back together — are the exceptions. So we are thrilled to report that the 9 week-old chick that was hooked in the leg, captured by our team, and placed on antibiotics by Wild Instincts to rid it of the resulting infection, was released on its natal lake last week and is now behaving normally. Indeed, Gabby saw it circle its lake three times in flight shortly after release.

Juvenile loons have a relatively short window during which they must: 1) learn to capture fish and invertebrates underwater, 2) learn to fly, and 3) develop large enough fat stores to migrate south to Florida for the winter. It seems remarkable that this youngster has bounced back from its dangerous encounter with humans to the point that it might be able to make the journey with its cohort.

We have reached the time in late summer when — following many trial runs, crashes and ugly landings — chicks have begun to fly. But chicks do not always take wing, circle and land in their own lake. They wander. The picture below was taken on September 17th by Bonnie Montgomery of Fifth Lake, east of Rhinelander. She caught the legs on a departing loon well enough that we could identify it (see two bands on right leg pointed out by green arrow) as one of the two chicks raised on Buck Lake, south of town.

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We have a keen interest in the local wandering of chicks like this one. Following our finding that loons settle on breeding lakes that are similar to their natal lakes, we are interested to see how this preference takes shape. Perhaps loons spend their entire lives preferring to live and forage in lakes of a certain size and water chemistry. If so, this lifelong predilection should make itself known early. That is, juveniles that begin to fly and visit lakes near to their natal lake should prefer lakes similar to the one on which they were reared.

Kristin and Gabby this year, Nathan last year, and Joel in 2011 have examined the hypothesis that natal site matching (as we call the preference of a loon to breed on a natal-like lake) is evident even in the local wandering of chicks. It will take a good deal of data to examine this hypothesis, but we are hoping that our crew will collect enough data (especially after this year’s bumper crop of chicks) to make statistical analysis possible.

Speaking of Kristin, Gabby and Joel, they caught another chick tonight that had become hooked in the neck by a lure and snarled in two types of fishing line. Luckily, the hook did not penetrate deeply. The lure was removed by Mark Naniot of Wild Instincts, the line was cut off of the bird, and the juvenile was released, still apparently in good health. 2013 has been a very bad year for loons and fishing!

A week ago, a fisherman hooked a juvenile loon in in the leg. We know the juvenile well; it is a chick that hatched 9 weeks ago whose parents and territory we have observed all summer. As a 9 week-old, this chick is close to adult size. At the time of the accident, it was feeding itself for the most part and beginning to practice taking off and flying. The fishing lure changed that. With a hook embedded in its left leg and monofilament line wrapped around the leg, the young loon no longer dove effectively and made painful and pathetic efforts to fly. Fortunately, our team captured the chick last night. A round of antibiotics and feedings, administered by Wild Instincts, might give this youngster a chance to resume its development, regain its health, and ultimately head south with its brethren. We are hoping for the best.