Now we have the answer! From Jack Chiles Tuesday Bird Census for June 12, "The highlight of the day was discovering that the Least Terns have settled in, starting to nest."
The Refuge was ready, with two nesting platforms placed in Lake Texoma. (Photos were taken in 2015 by Rusty Daniel and Gary Hall)
Habitat for the Least Tern, as described by Cornell Lab of Ornithology on All About Birds is “Seacoasts, beaches, bays, estuaries, lagoons, lakes, and rivers, breeding on sandy or gravelly beaches and banks of rivers or lakes, rarely on flat rooftops of buildings.” You can add to that the two artificial nesting platforms at Hagerman, especially designed and built by Refuge employees for the Least Tern. Funding for the project was provided by Jetta Operating Company, Inc and the Nancy Ruth Fund.
The Least Tern, the smallest American Tern, is an 8 to 9-inch bird, with a black "crown" on the head, a snowy whiter underside and forehead, grayish back and wings, orange legs, and a yellow bill with a black tip. Males and females are similar in their appearance. The name “Interior” is attached to Least Terns who breed in isolated areas along the Missouri, Mississippi, Ohio, Red, and Rio Grande river systems. They winter in coastal areas of Central and South America.
Interior Least Terns at HNWR, photographed by Eileen Sullivan in June, 2011
The Interior Least Tern is endangered due to loss of habitat, primarily because of changes in river systems and competition from recreational development. Terns arrive at the breeding ground in late spring – early summer and spend several months there. According to Dr. Wayne Meyer, courtship behavior includes the male showing off a fish to potential females, see photo above. Nesting in small colonies, Terns scratch out a shallow depression in sand or gravel for a nesting spot. The female lays 2 – 3 eggs in 3 – 5 days. Parents take turns incubating the eggs for about 3 weeks; Dr. Meyer says that the female does the lion share of the incubating. Chicks hatch one per day and leave the nest a few days after hatching but continue to be fed and cared for by adults for about two months.
Nesting adults defend an area surrounding the nest (territory) against intruders. Intruders can include humans, coyotes, fox, raccoons, bobcats, domestic dogs and cats, American Crows, Great Egrets, and Great Blue Herons among other creatures. When defending a territory, the incubating bird will fly around giving an alarm call and diving repeatedly at the intruder.
Terns feed on small fish and aquatic creatures and can be seen hovering and diving for prey, as well as skimming for insects. The young have to learn these hunting skills during their "nursery" days.
Tern in flight, photographed by Mike Chiles
Terns usually return to the same nesting area year after year. Before the launch of Tern Island I and II, the birds chose the rocky surface of the pad roads for their nursery, completely vulnerable to predators and extreme summer heat; the successful hatch rate was low to none. However, they still had not taken to the presumably safer man-made nesting platforms in 2017; they produced 10 eggs and 5 live chicks, on the pad roads C and D.
Nesting Tern, photographed by Jack Chiles in 2011 on one of the Pad roads at HNWR.
Hopefully, the terns will have a successful hatch this year.
Thanks to Jack Chiles, Texas Master Naturalist, for the original post on Least Terns, July 13, 2011. Material has been updated in 2015, 2017 and 2018. In addition to All About Birds, information for this post came from Texas Parks Wildlife and from US Fish & Wildlife.