Thinking skeptically about loons

I've been thinking about loons lately. This is not hard do do because every time I turn around there is a loon either watching me fish, yodeling off in the distance, flying overhead, or feeding its babies just off to my right as I sit here writing stuff. This year, the pair of loons that lives in front of the cabin seems to be producing two offspring ... the young ones grew quickly to near adult size and seem fit and healthy as far as one can tell. Last year, the pair living here produced zero offspring.

I had thought the other day of writing something about loons in winter, in part because of all the people I see on a day to day basis here in Minnesota, I seem to be the only one who has seen the loons wintering, and to me it (the wintering) is rather remarkable. But this led me to do some additional reading about loons, and this in turn led me to encounter some information that made me put on the old skeptical thinking cap. So this is an essay about thinking skeptically, but also about bird lovers and how sometimes they don't, and about environmental denialism, adaptability, and possibly, evolution. In fact, as I starting putting this together, I realized that this needed to be the first in a short series of essays, as there is too much to put into one post.

Now, I'm not a loon expert. There are people who did their PhD on loons, and I did my PhD on something else. But I do try to be observant and I am a student of nature, and except for the years I was commuting between grungy apartments, windowless laboratories, and the rain forests of Central Africa, I think very few years in my life have passed with out loons. Over the last four years I've had the pleasure of closely observing a pair of loons at my wife's family cabin. From where I sit right now, and this is generally where I sit and write, I can see the tongue of land on which the loon nest is built. The nest itself is just around the corner and out of sight. I can see the entire feeding territory of these loons. There is a lake very near by that I think one of the loons occasionally flies to for some reason, but I'm not sure. But, I'm pretty certain that nearly 100% of the foraging that these loons do is within sight as I sit here. I can see the four loons now, across the bay floating near the aforementioned tongue of land, over a substrate that ranges from three to six feet in depth, rocky, with a reed margin. The loons are not particularly active at the moment, they are close to each other, and they are not yodeling. Also within sight is the breeding nest not currently in use and the roosting areas (very much in use) of the resident eagle pair, and although I cannot see it at the moment, the great blue heron is most like within 500 meters of the loon.

So, those are my loons. What I'd like to do now is to run down a set of observations that I've heard or read about and see how they fit with what I know from my personal observation of loons. As I do this, there is are a couple of questions to keep in mind. If there is a contrast between something I've observed and something I've read, is this because my observations are wrong? Is it because of natural variation in the system, so my observations are correct but I'm not getting the normative picture? Is it because the common knowledge, or the literature, about loons is biased in some way? Or, is it because loons and loon evolutionary and behavioral ecology is dynamic and things change? Most of the common loon knowledge and most of the literature I have laying around the cabin is from the 1980s. Now, I could go and get new information and just update it, but I thought rather that I'd stick with this information because I like the idea of comparing the Loon Gestalt of 1985 with what may be going on about 20 years later. I'm going to call the older information "Common Knowledge" and the other information, either my own observations or just stuff I've learned more recently, "Challenge." Then bird experts or loon-ologists can swoop in and have their way with me.

Common Knowledge: It is said that loons do a thing called the Broken Wing Behavior. This is where a parent loon senses a predator moving in on the young, and takes off, looking very much like a panicked bird with a broke wing, thrashing just over the surface of the water but not taking off. The idea is that the loon is saying "what would you want that baby loon for when you can easily get this pre-wounded large morsel of food over here!"

Challenge: I've seen this behavior many times in my loons. I have only seen it during the beginning of the season when the loons have arrived and are setting up their pair bond, along with lots of other displays. One year there were three adult loons, two of which fought with one apparenly killing the other. During this fight, which lasted for days, the loons did this broken wing display many times. It is not unusual for a display that appears to have evolved for use in one context gets used in another, especially if that secondary context is mating display. But, if I had never learned (from Common Knowledge) about the broken wing display as a predator avoidance strategy ... and I remember learning about that when I was a very young child from a TV show on loons or northern lakes or something ... I would never have guessed that this is what it was. Indeed, the behavior itself does not look anything like a damaged or less dangerous loon. It looks like a pretty impressive loon that can beat the water with one wing as it flies along with the other dragging against the surface and making a nice wake. Wow. Better leave that loon alone. Or mate with it. Or whatever.

The anti predator behavior I have seen, used against the eagles that seem almost always in sight as well as the resident great blue heron, is to yodel at the offending attacker, move in closer to each other, and look like a loon. A loon is a big bird with a big head. They are heavy (for birds) and have a nasty beak and a strong neck. I think that a loon could do some serious damage to an attacking eagle. I think the eagle gets this.

A secondary anti-predator behavior I've seen, which seems to be more a matter of direct interference competition but could be used as such, is the attack-from-underneath behavior. I've not seen this described elsewhere so maybe it is just my loons that do it. In this behavior the loon swims underneath a duck (often but not always a merganser) and shoots up like a Polaris missile from below. Usually the ducks are in a group. This scatters the ducks, and is actually quite fun to watch.

So, in the end, I know loons do this behavior, but I'm not entirely convinced that it is primarily an anti-predator tactic.

For the next edition of Thinking Skeptically about Loons, we'll look at lead poisoning.