An Imperial Beach Hidden Gem and Bird of the Week, the Royal Tern
May 25, 2017 09:38AM
● By Paul Spear
An Imperial Beach Hidden Gem and Bird of the Week, Bryan Brillhart Photography present the “Dig IB” Bird of the Week, the Royal Tern
The column will provide a picture of a bird(s) locally photographed and we will have background on the bird.
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Royal Tern (Thalasseus maximus)
This week’s “Bird of the Week” is the Royal Tern (Thalasseus maximus). Common along tropical and subtropical shores, the Royal Tern is a characteristic sight along the Gulf Coast and southern Atlantic Coast, and are less numerous in California. Aside from a few interior localities in Florida, it is almost never found inland except after hurricanes. Populations
declined seriously in late 1800s and early 1900s when eggs were harvested from many colonies for food. These terns made a substantial comeback during the 20th century, but are still vulnerable due to loss of nesting sites. Populations have declined in California since 1950, coinciding with the decline in the population of the Pacific sardine.
This is a large tern, second only to Caspian Tern, but is unlikely to be confused with the carrot-billed giant, which has extensive dark under wing patches. The royal tern has an orange-red bill, pale grey upper parts and white under parts. Its legs are black. In winter, the black cap becomes patchy. Juvenile Royal Terns are similar to non-breeding adults. Differences include juveniles having black splotched wings and a yellower bill. An adult Royal Tern has an average wingspan of 130 cm (51 in), for both sexes, but their wingspan can range from 125–135 cm (49–53 in). The Royal Tern's length ranges from 45–50 cm (18–20 in) and their average weight is anywhere from 350–450 g (12–16 oz). The calls of the Royal Tern are usually short, clear shrills. Some of the shrills sound like “kree” or “tsirr”; the Royal
T ern also has a more plover like whistle that is longer, rolling and is more melodious.
Habitat is on coasts, sandy beaches, and salt bays, favoring warm coastal waters, especially those that are shallow and somewhat protected, as in bays, lagoons, and estuaries. They are also found well offshore at times, and travel freely between islands in the Caribbean. They usually nest on low-lying sandy islands.
Royal Terns usually first breed at the age of 4 years. Nesting is in colonies. Courtship involves high spiraling flights by two or more birds. On ground, males present food to females; both birds bow and strut in circles. Nest sites are on the ground (usually sandy) in the open. Nests (probably built by both sexes) are a shallow depression, with or without a sparse lining of debris.
Royal Terns forage mostly by hovering over water and plunging to catch prey just below the surface, sometimes flying low, skimming the water with their bills, they occasionally catch flying fish in the air, or dip to the water's surface to pick up floating refuse. They are known to steal food from other birds, and sometimes feed at night.
Feeding mostly on small fish (up to 4" long, sometimes up to 7") and crustaceans, especially crabs, they eat a wide variety of small fish, shrimp, and squid. Soft-shelled blue crabs are a major item in their diet on the Atlantic Coast.
After mating females lay one, rarely two whitish to brown, blotched with reddish-brown eggs.
Incubation is by both sexes in about 28-35 days, but usually 30-31. Within 2-3 days after hatching, young leave the nest and join others in a group called a "creche." Both parents bring food. Parents and offspring are able to recognize each other by voice, so that adults feed only their own young. Age at first flight is about 4-5 weeks. Young remain with parents for up to 8 months or more, migrating south with them.
I spotted a large flock of Royal Terns this winter near the Tijuana River mouth. You never know what you will see there. Get out for a walk on the beach or on the many trails in the Estuary, and until next week, happy birding!###