Terns still looking after their young

Caspian terns in mixed flock by Lindsay Addison

At inlets in southeastern North Carolina, mixed flocks of Royal, Sandwich, Caspian, Common, and Forster's Terns are gathering. At high tide they cover exposed sandbars in their numbers, and they fill the air with plaintive cheeps. The cheeping is the work of the young Royal, Sandwich and Caspian Terns that hatched this spring and summer and are working hard to get their parents’ attention in the hope that Mom or Dad will provide a meal.

Not only are terns attentive parents when their chicks are downy and flightless, they continue to feed their young into the fall as they stage for migration and move south. In fact, Sandwich Terns have been seen feeding fledglings on their wintering grounds, and Royal and Caspian Terns migrate with their young and may feed fledglings into late winter or early spring of the next year. It’s easy to spot a tern youngster. Their wings and backs are gray like the adults’, but more patterned with black and dark gray, so they will stand out upon a quick scan of a flock. They also continue to adopt the begging posture, hunching up their necks and crouching low in front of the adults.

Just today several young were working their parents over at Lea-Hutaff Island, hoping for a tidbit. Several adults flew overhead carrying fish and shrimp in their bills. When they are not in the mood to respond to their chicks’ begging, instead of providing a fish, adults will turn away looking for all the world as though they are trying to ignore a persistent kid pleading for candy at the check-out line.

The extra food tern parents provide has a serious side, though. While the fledglings take care of themselves and do catch their own food, mortality is higher for first-year terns than for adults of two or more years. Among Royal, Sandwich, and Caspian Terns estimates of first-year survivorship vary depending on the parameters of particular studies, but they range from less then 50% when chicks are included to around 80% when looking at chicks from fledging on. Meanwhile, rates of adult survivorship from year to year can exceed 90%. So, when adults can make the first winter easier for their offspring by extending the period of time they provide care, they might be giving them a crucial leg up.

-- Lindsay Addison




How you can help, right now