Where Our Loons Are Now

We have had an exciting last few weeks. First, our paper on population decline in northern Wisconsin has been the most frequently read paper in Condor: Ornithological Applications every single day during the past three weeks. Of course, I jinxed it, and when I looked just now I found that we have fallen and are only the second-most read paper! In any event, we seem to be getting the word out about problems that loons are facing in the Upper Midwest.

Second, Brian Hoover’s paper that describes and explains lake preferences of juvenile loons — those that have just fledged and become independent of their parents — has just come out. Brian’s paper shows that juveniles tend to visit lakes that have similar pH to their natal lakes and also that they use large lakes with a variety of fish species present. In other words, if we are to preserve the Upper Midwest loon population, we must look out not only for lakes where loons nest but also those lakes nearby where juveniles fatten themselves up to prepare for migration.

Third, our collaboration with Sarah Saunders of Audubon has borne fruit; Sarah’s paper has just been accepted by Journal of Animal Ecology and should appear as an accepted article in the next week or two. Her model, which combined measures of land use, climate, and our study population, indicates that the North Atlantic Oscillation — a fluctuating climatic pattern that is projected to increase under climate change — is having a net negative impact on both adult loon survival and chick production in northern Wisconsin. The pattern is complex, but it dovetails logically with the population trends we have seen in northern Wisconsin. The simplest interpretation of her findings is that the North Atlantic Oscillation affects food levels on the loons’ wintering grounds, which, in turn, impact survival and subsequent chick production. Sarah also found that increased human development reduced adult loon survival. Most alarmingly, Sarah’s simulations of the next decade all project decline for the northern Wisconsin population, just as our Condor paper did. So, we must look for more ways to boost loon breeding success and adult survival on the breeding grounds in an effort to counter what is a most worrisome trend.

Sarah’s findings place new urgency on my efforts to understand all 12 months that constitute a year in a loon’s life. Most recently, I have batch-plotted recoveries of loons banded in northern Wisconsin that covered distances of more than about 200 miles. As you can see from the featured image above, we have a lot of these data. (You might have to click on the title in the e-mail to see the map.) Leaving aside the small number of interesting shifts westward and northward, the photo confirms the wintering pattern that I mentioned in a recent post. Our Upper Midwest loons winter in large numbers along both coasts of Florida — especially the Gulf Coast. About a quarter of our loons, however, winter off of the Carolinas, especially North Carolina. Concerned as I am with the increased rate of mortality among adults in recent years, I cannot help thinking that hazards along these coastlines are creating trouble for them. Clearly while I can use the fall, winter, and early spring to rest and recover after intense field work during May, June, July and August, my study animals do not have that luxury.