Birdwatch

Forster’s Tern

Acrobats of the autumn air

By Susan Campbell

It is the cooler time of the year — and not when you would expect to see terns along our coastline. In summer, there is an abundance of common, gull-billed, royal, Caspian and least terns along the beach. Truthfully, the variety is only evident to non-birders by the array of vocalizations of these fast-flying birds. Terns, with their unique patterns of dark and light plumage as well as bill coloration, are often thought of as the diminutive cousins of gulls: also being primarily fish eaters and associated with saltwater.

The Forster’s tern, a medium-bodied species, can actually be found in eastern North Carolina year-round. Indeed, in winter they are seen patrolling the breakers for their next meal. Individuals or small flocks will forage in saltwater habitat for small fish or larger invertebrates from late summer through spring. Their acrobatic diving is eye-catching no matter the season. Individuals patrol shallow waters watching for prey, which can range from jellyfish to starfish and crabs to smaller fish such as mullet.

Forster’s terns are not the easiest bird to identify — especially in the winter months. Both adults and first winter birds have a black eye crescent, pale gray upper parts, red legs and a dark bill. Unlike other tern species, these birds actually have very limited dark markings on their wings. The blackish coloration is only evident on the very tips on the dorsal surface of the flight feathers. Their short bills are only moderately thick. And the tail is noticeably forked but not terribly long: only such that it projects just slightly beyond the wing tips when the bird is perched.

Interestingly, although this species breeds in a variety of freshwater habitats in the interior of the U.S., it can also be found nesting in marshes of our coastal plain. The percentage of our wintering population that is made up of long-distant migrants from the Great Plains and/or Canadian provinces is unknown. However, it has been long recognized that these birds change their habitat and food preferences seasonally. Although speculative, it is possible that local Forster’s terns are precluded from feeding in salty locations specifically by common terns in the summer months. With the competition absent in cooler weather (i.e., common terns have departed for the tropics), their feeding grounds are significantly less restricted.

Certainly if you are away from the coast between October and March, Forster’s is the most likely tern that you will encounter — and possibly in large numbers. Inland reservoirs such as Jordan Lake (in the Triangle area) host hundreds to thousands of these terns each winter. However, in these locations, miles from saltwater, terns of any variety are a treat.  b

Susan would love to receive your wildlife sightings and photos. She can be contacted at susan@ncaves.com.

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