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.
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.
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.
Publishing papers in scientific journals is hard work. It requires patient and well-planned data collection, thoughtful statistical analysis, and painstaking writing and editing of a manuscript. And then the real work begins! Among the dozens of scientific journals that might publish the paper, one must select a journal that suits the topic of the paper, employs competent editors and reviewers, and makes its published papers available to a wide audience so that it will be read and cited by many colleagues in one’s field. Most crucial, one must convince the journal’s anonymous reviewers that the findings reported in the paper are robust and valuable. In short, publishing a paper is a journey.
Recently, we completed a successful journey, as our paper describing the process of territory settlement in young loons was accepted by Animal Behaviour. Although we would like to celebrate this event, we are more relieved than joyous; relieved because the paper represents a vast amount of field work, number-crunching and writing and became long and unwieldy enough that it earned harsh criticisms from some reviewers. So its publication became, as some journeys do, a story of survival in the face of adversity.
The paper will make available a trove of valuable findings. We report in the paper that young loons do not adhere to the most prominent model for territory settlement. This idea, termed the “foothold model”, maintains that young animals in search of breeding territories target a small set of established territories for intrusions, gradually gain confidence through increased familiarity with that limited set of territories, and then evict the owner of one of those territories (or outcompete another young loon for the vacancy, in the event of the owner’s death) in order to claim the territory as their own. We show in our paper that, instead of using a foothold of this kind to gain a territory, young loons merely settle on a territory that is similar to their natal one. In some cases, they are able to occupy a vacant territory and breed there. In other cases, they wait to mature and improve in body condition and then evict an owner. But the repeated intrusions that young loons make to specific lakes are not attempts to build upon their familiarity with the lake and thereby increase their competitive ability there. Rather, they are efforts to assess the fighting ability and perhaps the motivation of the current owner to defend its territory so that the young loon can judge when an attempted eviction is likely to be successful. Reviewers described our findings as “provocative” within our field, and we hope they are right!
Thanks to all our supporters, especially landowners and friends, who allowed us to study their loons year after year. Publication of this meaty paper is evidence that our mutual investment in loon research is paying off.
Well, the loons are gone from the study area. I know we all miss them. Each year I mourn after the loons migrate south and we all have hunkered down for the winter.
But research goes on. I am in the midst of an analysis to learn whether loons that have settled on one lake and bred there — either successfully or not — choose a second breeding lake that is similar to the first. What I am asking here, in effect, is whether a loon learns what constitutes a good breeding lake through its reproductive efforts and applies what it has learned in subsequent reproductive attempts. For example, a loon might first settle on a very clear lake, adapt to foraging on that lake, and then look for a second lake that is also clear. We have preliminary data to suggest such a pattern. If loons do learn what features of lakes are helpful to breeding, and fine tune their lake choices on the basis of their first territory settlements, this would be an interesting and important advance in the study of habitat selection. It would also add to our recent finding that loons initially choose to settle on breeding lakes that match the lakes on which they were reared.
I will let you know what I find out about territory settlement as the work progresses. Meanwhile, enjoy these nice photos from Linda Grenzer, who tracked the breeding female from her lake onto Bridge Lake this fall and caught her molting.
The July 4th issue of Nature notes our finding of natal-site matching in their “research highlights” section. This is really exciting for the project. It demonstrates how valuable a study population we have, as we are able to gain insights into habitat selection behavior that most other studies cannot. The finding reported in the article has the potential to change the ways ecologists look at territory settlement, as it runs counter to the prevailing viewpoint in the field. Briefly, current theory suggests that young animals looking for breeding territories try to choose those that are likely to maximize offspring production. Our results in loons suggest that, in contrast, young animals are looking for breeding territories similar to their natal lakes, because such territories might maximize their likelihood of survival.
We were pleased to be included in a list of recommended readings that accompany a popular animal behavior textbook. Our article, which is available here, summarizes in non-technical language the findings of our study over the past ten years or so. Naturally, the editors of the readings could not resist using our photogenic study animal for the cover!
Great news! Our manuscript that describes natal site matching was just accepted for publication in a prestigious ecological journal. Very exciting to get the story out there that young loons have a strong statistical tendency to settle on breeding lakes that match their natal lake in both size and pH.
From the field….about half of our breeding pairs are now incubating eggs. Although blackflies are moderately bad, they do not seem to be terrorizing the loons enough to cause them to abandon their nests. I am anticipating a good year for reproduction in Oneida County. (Fingers crossed, as always.)
Our article on juvenile survival in loons just came out. Based on the hundreds of loons that we banded as chicks and have reobserved as adults in the study area, the paper reports that about half of all loon chicks return to the breeding ground as adults. Most of these individuals are seen within 15km of their natal lakes.