No, I am not talking about the Buccaneers. Kansas City and Tampa are both far from anywhere I have spent meaningful time. Besides, KC won last year, and Tom Brady has won countless times. Enough already!
I am talking about Tampa Bay the place — the large, protected inlet halfway down the west coast of the Florida peninsula. Loon enthusiasts should love Tampa Bay because it serves as the wintering grounds for a good many loons from the Upper Midwest. In fact, so far 33 of 53 recoveries of loons banded by the Loon Project and others in the Upper Midwest — sadly, these are mostly loons found dead on the beach or elsewhere and reported to the Bird Banding Lab in Maryland — have come from Florida’s Gulf Coast, between Pensacola and the Keys. By chance, or more likely just because it is an area of dense population, a good percentage of these birds come from the Tampa Bay area.
This is not a brand new finding. Kevin Kenow of USGS has used satellite transmitters to track loons from Minnesota, Wisconsin, and Michigan and reached the conclusion that Florida’s Gulf Coast is a vital wintering area for our birds. He puts the percentage of Upper Midwest loons that winter there at above 70%. So we have two separate lines of evidence that tell the same story about the wintering location of Upper Midwest loons. Well, okay, you must be thinking, our loons have to winter somewhere. Why does it matter where exactly? It matters because, while we only see them in the summer and tend to focus only on their trials and tribulations during summer, our loons must also survive on their southward migration, sustain themselves on the wintering grounds, and then make it through another northward migratory journey in order to get back to us each year. Of the period during which it is out of our sight, a typical loon from our area spends four to five months on Florida’s Gulf Coast.
When you learn where breeding animals are spending their winters, conditions on the wintering ground suddenly get very real. During the past two decades, ecologists have improved in the ability to track individual animals (usually birds) from breeding to wintering locations, using such tools as satellite transmitters and geolocators. They have also learned that migratory trips do not somehow “reset” an individual so that all individuals that have migrated to the breeding ground start on equal footing. Instead, a difficult (or easy) migration or wintering period leaves a lasting imprint on an animal, placing it at a disadvantage (or giving it an advantage) during the next phase of its life history. Such impacts are called “carryover effects” and have become hot topics for investigation. Surges or declines in breeding populations, we now see, can be as easily explained by events on the wintering grounds as those during the breeding season.
We are at an early stage in our analysis of breeding season impacts on wintering loons and vice-versa. In fact, we know nothing about carryover effects in loons. But now that we are zeroing in on wintering locations of loons from different breeding populations, the stage is set to look for such patterns. At the moment, I have set my sights on a less lofty goal. You might recall my post in June 2020, when I pointed out how many adult loons had failed to return to Wisconsin in spring of 2020 after leaving in fall 2019. The simplest explanation for this very low return rate of Wisconsin breeding adults is that some event occurred during the winter of 2019-2020 along the Florida Gulf Coast that killed many loons there. More broadly, I have begun to explore data that Florida wildlife officials collect annually on red tides and other environmental events that threaten ocean-dwelling animals. Could fluctuations in annual survival rates of loons in Wisconsin be explained by mortality events recorded along the Florida Gulf Coast?