Good Morning Gloucester

FISHING FOR SEX

Or is it Sex for Fish? –The Quid Pro Quo Courtship of the Least Tern

While learning more about Piping Plovers on North Shore beaches I happened to be on Winthrop Shore Beach on an afternoon in May when dozens and dozens of Least Terns were pairing up in an elaborate dance of courtship and mating. It was fascinating to observe their courtship feeding and I was so curious to learn more.

That very same afternoon, the “Rosetti’s” Piping Plovers were mating, too. Well known to the area is a pair of Plovers that nest every year directly in front of Café Rosetti’s, a fabulous Italian restaurant located on the main boulevard that runs along the beach. The Rosetti’s Plovers are very successful and each year they fledge a clutch of chicks. This year was no exception!

For the past several months I have been documenting through film and photographs the Rosetti’s Plovers and the Rosetti’s Terns, along with a family of PiPl at Revere Beach (more about the Winthrop and Revere Beach’s PiPl in future posts). Both species of birds are on the state and federal threatened species list. Piping Plovers and Least Terns began nesting on the area’s urban beaches as a direct result of the Boston Harbor cleanup, a wonderful, and very surprising to all involved, turn of events. In some regions, both species share the same habitat, as is the case with Winthrop Shore Reservation.

The more we learn about how and why Plovers (and other species of threatened shorebirds) successfully nest on other north of Boston much loved and much utilized beaches, the more we can help our Good Harbor Beach Piping Plovers successfully nest in years to come.

During the breeding season Least Terns perform courtship displays in the air and on the ground. In dramatic aerial display, a fish-carrying male is chased by the female, sometimes up to four females.

On the ground, the male parades his fish to a prospective mate. With fish dangling from his bill, he bobs his head from side-to side, then opens and closes his wings over the female.

The male mounts the female, still with fish dangling. During copulation he passes the fish to the female.

The funniest thing is, when the female allows the male to mount, she sometimes snatches the fish and flies away before mating has occurred.

No privacy, and lots of piracy!

The male continues to feed the female throughout the incubation period. Both parents incubate the eggs however, the female does about eighty percent of the brooding, while the male provides most of the fish for she and the chicks.

When one adult Least Tern feeds another, whether during courtship when the pair are first becoming established, or during the incubation period, this behavior is called “courtship feeding.”

The courtship feeding display perhaps provide the female tern the assurance that her male mate will be a good provider of fish for both she and the young. Both male and female Least Terns feed the chicks for the first several months after hatching; the better the fisherman, the stronger the chicks. Studies have shown too that courtship feeding provides the female with considerable nutritional benefit. The number of eggs, and weight of the eggs, are determined by the female’s nutritional status and how much food is fed her by her mate.

In Massachusetts, Least Terns primarily eats fish, including Sand Lance, Herring, and Hake. They also eat insects and crustaceans.

And we have a nest, with two eggs!

Read more about Winthrop Shore Reservation here.Winthrop Shore Reservation Nesting Bird Observers