A strange sight over the marsh

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From the marsh at the head of the bay, it arose, as a dark cloud lifting from the tall grasses. The dawn was faintly lighting the eastern sky behind the amorphous form as it undulated and shifted, gradually gaining altitude. The only thing I had ever seen that looked anything like this was a “murmuration” of starlings on a television nature series.

The phenomenon typically occurs as a predator avoidance strategy and there is usually a falcon harassing the flock. In this case, there was no hungry raptor nearby and these were not starlings. It was a massive flock of tree swallows, answering the wake-up call of dawn and resuming their age-old migratory journey.

For several days, each year in late winter I see unending streams of these small birds flying low over the water along our Panhandle shores. I was lucky enough to be in a boat on the Apalachicola River that day, at the precise time this flock left its evening roost. I am reminded of that stunning vision as I drive to work during late February each year and see distant relatives of these same birds streaming along our coastline on their annual journey.

According to Cornell University’s “All About Birds” website, tree swallows overwinter in the southern U. S. and down into Central America and Cuba. The birds I see are typically heading east along the water’s edge. This means they must be part of the group that winters in south Florida or Cuba.

In spite of their gregarious nature during migration, tree swallows are not colonial nesters like their cousins the bank and cliff swallows. As their name implies, they are tree-nesters and require a cavity made by some other species. Woodpeckers often construct the cavities but tree swallows will use human-made nest boxes, the eve of a building or even holes in a riverbank made by the bank swallow.

As with all swallow species, they eat primarily insects, but have also been known to consume some plant berries during winter such as wax myrtle. Protection of dead trees throughout their breeding range is an important conservation measure as this is by far the most important nesting habitat.

A dark cap and upper body characterize adult birds, while the underneath is solid white. When the sun hits at the correct angle, a deep blue iridescence is revealed (more so in males). First-year juveniles are dull brown above and white below. No other swallow species in North Florida will be seen migrating in such large numbers along the coast so you keep your eyes peeled along our coastal highways for these long-distance migrants.

Find a safe pull-off spot before you get too enthralled with the spectacle and take some time to enjoy the show. When you get ambitious, visit one of our expansive coastal marshes at the crack of dawn during February (Brrr!) and look for a whirling, writhing swarm which proves to be a real show-stopper.

Erik Lovestrand, the UF/IFAS regional Sea Grant agent in Wakulla, Franklin and Gulf counties, can be reached at elovestrand@ufl.edu

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