Royal terns are a species of seabird found across much of the Americas. They are large, graceful birds with distinctive orange-red bills and a shaggy black crest on the top of their heads. Royal terns get their name from the ornate, feathered “crowns” on their heads, which resemble the ceremonial headwear of royalty.
These medium-large terns breed in colonies on sandy or rocky beaches and islands along the Atlantic and Pacific coasts, as well as on islands in the Caribbean Sea and Gulf of Mexico. They spend their winters along coastlines from the southeastern United States to Brazil.
Royal terns are classified as “least concern” on the IUCN Red List of Threatened Species. This means they have a large global population and are not currently at risk of extinction. However, in some regions their numbers have declined due to threats like habitat loss, pollution, and disturbance of nesting colonies. Understanding royal tern population trends and implementing conservation measures are important for ensuring the long-term survival of this species.
Royal Tern Description
Royal terns are elegantly built birds with long, narrow wings and shortish tails. Adults range from 40 to 50 cm in length and have a wingspan of about 95 to 105 cm. They weigh 300 to 400 g on average.
The plumage of adult royal terns is pale gray above and white below. The crown and long, shaggy crest are jet black. The stout bill is bright orange with a black tip. The eyes are dark with white eyerings, and the legs are black.
Male and female royal terns look alike. Juvenile birds have a black bill and eyes, pale gray plumage, and a smaller crest. By their second year the young terns resemble the adults except for having some black flecking in their crest and a paler, yellowish bill.
In flight, royal terns appear buoyant and graceful. Their long, pointed wings beat leisurely as they soar and glide. These birds are very vocal, with loud, rolling and grating calls. They use their sharp bills to plunge-dive for small fish, which make up the bulk of their diet.
Royal Tern Range and Habitat
Royal terns have an expansive breeding range across coastal areas in the Americas. In North America they nest along the Atlantic coast from Nova Scotia to Florida, around the Gulf of Mexico, and along the Pacific coast from California to Mexico.
There are also breeding colonies in Central America, northern South America, and throughout the Caribbean. After nesting, royal terns migrate down the coasts of Central and South America to overwinter as far south as southern Brazil.
These terns frequent nearshore ocean waters, sandy beaches, barrier islands, sandbars, and coastal lagoons. They require flat, open, sandy or gravelly sites for nesting in colonies. Nesting habitat includes beaches, shell banks, rocky islands, dunes, and dredge spoil islands.
Royal Tern Population and Conservation Status
The global population of royal terns is estimated to number 130,000 to 170,000 mature individuals. Their numbers today are considered stable, though some regional populations saw declines in the mid-20th century before rebounding in recent decades.
The species is classified as Least Concern on the IUCN Red List of Threatened Species. This indicates it is not currently vulnerable to extinction at the global level. However, royal terns face threats in parts of their range from human disturbance, habitat degradation, and predation. They are considered a Species of Special Concern in California due to population declines there.
Major threats to royal terns include:
– Disturbance and destruction of nesting colonies by humans and predators. Royal terns nest in dense colonies that are highly vulnerable to disturbance. Increased human recreation on beaches near colonies can cause nest abandonment. Predation pressure also reduces productivity.
– Habitat loss and degradation from shoreline development, erosion, invasive plants, etc. Breeding royal terns require undisturbed beaches and islands with little vegetation. Habitat loss reduces the number of suitable nesting sites.
– Environmental pollution. These birds are vulnerable to oil spills, chemical contamination from industrial discharge and agricultural runoff, garbage, plastics, etc. Pollution can poison birds and degrade their habitats.
– Extreme weather. Hurricanes, storms, flooding, and other extreme weather events directly destroy nests and can lead to colony abandonment. Sea level rise due to climate change threatens nesting habitat in the long term.
Royal Tern Behavior and Biology
Royal terns are highly social and breed in colonies that may contain just a few dozen to thousands of pairs. Nesting peaks vary across their range but occurs mainly from April to August.
Both sexes help build a simple scrape nest in the sand, gravel, or shells of the colony site. The female lays 1 to 3 pale greenish-blue eggs with dark brown markings. Incubation lasts about 4 weeks and both parents take turns sitting on the eggs.
Chicks hatch over a 2-3 week period. They are cared for by both parents and fledge at about 5 weeks old. Young royal terns stay with the parents for a period after fledging as they learn to fish and fly skillfully.
These terns feed by plunge diving for small fish such as anchovies, herring, and silversides. They may fly up to 20 miles offshore from the colony to forage. Royal terns also regularly steal fish from other seabirds. They are graceful flyers and sometimes soar high in the air to locate schools of fish.
Adults and juveniles form large staging flocks during migration and on the wintering grounds. They are highly gregarious at all times. While breeding, pairs engage in elaborate mating rituals, including aerial displays, parading, and offering fish gifts.
Key Facts
Here are some key facts about royal terns:
- Species name: Thalasseus maximus
- Conservation status: Least Concern
- Population: 130,000 – 170,000 mature individuals
- Body length: 40 to 50 cm
- Wingspan: 95 to 105 cm
- Weight: 300 to 400 g
- Lifespan: Over 20 years
- Diet: Small fish
- Range: Coasts of the Americas
- Habitat: Sandy beaches, barrier islands, coastal lagoons
- Nesting: Dense colonies of hundreds to thousands of pairs
- Clutch size: 1-3 eggs
- Incubation: Around 28 days
- Fledging period: 35 days
Comparison to Other Tern Species
Royal terns belong to the family Laridae, which includes gulls, terns, noddies, and skimmers. There are over 40 species of terns worldwide. Here’s how royal terns compare to some other common tern species:
Caspian Tern
Caspian terns are larger, have a heavier red bill, and lack a shaggy crest. They occur along inland lakes and rivers as well as coastally.
Elegant Tern
Elegant terns have yellow bills with black tips and winter further south than royal terns along the Pacific Coast. They have smaller crests.
Sandwich Tern
A European species with a black crest tip and yellow-tipped black bill. Sandwich terns are occasional vagrants along the U.S. Atlantic Coast.
Common Tern
Our most widespread tern. Common terns are much smaller with gray upperwings, a black cap, and reddish legs and bill.
Forster’s Tern
Forster’s terns have white heads, gray backs, long tail streamers, and orange-red legs and bill. They occur widely across North America.
Least Tern
Our smallest tern. Least terns have a yellow bill with black tip, white forehead, and black cap and eyeline. They nest inland on river sandbars.
Conclusion
In summary, royal terns are elegant, crested seabirds found across coastal areas of the Americas. They nest in large colonies on beaches and islands and plunge dive for small fish.
Royal terns have a broad global range and large total population. They are not currently threatened with extinction but do face regional pressures from human disturbance, habitat degradation, and other factors. Maintaining protected breeding sites will be important for conservation of this iconic seabird.