I often thank my lucky stars that I am a field biologist. Being outdoors, especially in Wisconsin, is a huge perk of my profession. There is something thrilling about being in a situation where nothing is planned and anything can happen. Yet as glorious as it is to be outdoors, field work is perilous. Although I might tell the National Science Foundation, or Chapman, or the U. S. Geological Survey (who provide leg bands) that I have much of loon behavior figured out — that I have systematically tested all hypotheses and eliminated all plausible alternatives — I never feel confident when I am watching loons. They invariably surprise you by doing something that defies explanation. “What does that adult have to gain from wailing so often and so loudly when there is no other loon nearby to hear it?” or “Why is that loon wasting time alarm calling at the harmless muskrat?”. Rarely does a day in the field go by when I do not scratch my head at least once at inexplicable loon behavior.

Paradoxically, the best place to be when you are trying to figure out why animals behave as they do might be in your office, crunching the numbers, without any animals in sight. Free of distractions and laser-focused on the data, sometimes you discover a pattern that gives you a clear answer to a central question.

That happened to me yesterday. I was puzzling over a weird finding. In the midst of analyzing patterns in territorial intrusion, I was surprised to learn that territorial loons intrude more often into neighboring territories with chicks than do young, non-territorial floaters that are looking to settle on a territory. How on Earth could this be so? Floaters are young adults that are on the prowl. They search widely for territories with chicks, use those chicks as a badge indicating a good territory, and then return to try and evict a pair member in order to seize the territory for themselves. So it is floaters, not territory holders, that should be obsessed with finding, visiting, and competing for territories with chicks. Territory holders should have as their priority simply holding onto the territory they already own.

I must point out here that intrusions into territories with chicks, regardless of which loons make them, are generally a bad idea. As many of you have seen, territorial loons do not appreciate landings or close approach by intruders when they have chicks to protect and are much more apt to attack intruders at such times. This fact only thickens the plot. Now we must try to understand why a territory owner — a loon with something valuable to lose — would take a chance at being injured by visiting a nearby territory with a super-aggressive owner!

Lacking any other obvious path forward, I dove even more deeply into the curious tendency of territorial loons to seek out neighbors with chicks. Late in the breeding season, territory owners can be partitioned into two groups: those with chicks and those without. So I could look to see if, as one might predict, territory owners that had failed to raise chicks — and who therefore might be looking to trade up to a better territory — were those most likely to intrude. But quite the opposite was true. Territory owners rearing chicks of their own were much more likely to intrude at neighboring lakes with chicks than were territory owners that had no chicks.

As it happened, I discovered this last vexing pattern late in the day and could not dwell upon it. At 2:32 a.m. — during that inevitable hourlong period of sleeplessness that comes each night — I figured it out. While successful rearing of chicks is the ultimate goal of an adult loon’s life, chicks pose a great hazard too. To a floater, a territory owner’s chicks signify a high-quality territory, and so chicks raised in one year guarantee the owner will spend the next year fending off eviction attempts from floaters. It follows that owners should take any and all steps they can to keep floaters from learning about their chicks. Simply decamping and leaving your chicks alone during early morning is a good strategy, because floaters learn about chicks chiefly after spotting their conspicuous parents on the water and landing near them. If you are not on your territory, then no floater is likely to find your hidden chicks. But being away from your own territory and also intruding into your neighbor’s territory is doubly beneficial for a loon with chicks, because your presence will draw other adults to the neighbor’s territory (and away from your own territory nearby) and increase the likelihood that your neighbor’s chicks will be the ones that are spotted. That is to say, neighboring pairs with chicks seem to be locked in a desperate, reciprocal effort to expose each other’s chicks to floaters in order to protect their own territory ownership.

As I write this, I am listening to the hideous whine of a circular saw next door. Our own neighbors have contracted with the loudest and most inefficient construction crew west of the Mississippi to renovate their home. I find the noise, the clutter, the truck traffic, and the ceaseless cursing and shouting tiresome, to say the least. But I am fairly confident that our neighbors are not conspiring with outside forces to get us evicted. So I guess we have it pretty good.