It has been awhile since my last post. Sorry about that. With our study animals hunkered down in the Atlantic — mostly off of Florida — there has not been much to write about. But they are molting now, beginning to vocalize, and are readying themselves for a return to Wisconsin. Although the northern weather is not cooperating at the moment, our study animals will soon begin winging their way north.
Even after the summer, though, we accumulate data on our birds. How? By receiving reports of recoveries of our loons during migration and on the wintering grounds. Now, a “recovery” is, in essence, an unpleasant event. The term refers to a report of a bird banded with a U.S Fish & Wildlife Service metal band that has died, been found, and been reported to the Bird Banding Lab in Patuxent, Maryland. I get an e-mail from the BBL each time someone recovers one of the loons we banded. When I see the BBL address pop up on my phone, my pulse races, as I fear that one of our valuable breeding birds may have died. Each time we lose a loon that we have known and studied for 15 years or so, I grieve a bit. This happened two years ago when I learned that the long-time breeding male from Hancock Lake had died. More often than not the news from the BBL is sad but not devastating, as most of the recoveries are of first-year loons — birds we banded as chicks the previous summer that did not survive their first fall migration or winter. We are always sad to lose a bird we banded, but we understand that its first months of life pose a severe test for a loon, as it must complete migration, learn to forage in the ocean, and face a set of dangers to which it is unaccustomed.
Something positive emerges from recoveries. As we accumulate a record of which first-year loons have died and which have survived, we have a chance to confirm a pattern that we detected recently from our summer work. Young hatched on small, acidic lakes return to the breeding grounds at a lower rate than those hatched on large lakes of neutral pH. We do not yet know at what point this difference in mortality occurs. Do juveniles from small, acidic lakes fail to make it off of the breeding grounds? Do they die disproportionately during fall migration? Or do they tend to die in larger numbers after reaching the wintering grounds? Recoveries of these young birds during late summer, fall migration, and winter — as sad as they are — can provide us with the valuable answer.