Increased Admittance of Royal Terns

provided by Clinic for Rehabilitation of Wildlife

Royal terns (Thalasseus maximus) are quite deserving of their common name. In fact, a flock of royal terns is referred to as a “highness”. These shorebirds sport a black crested-crown that, as they grow into adulthood, will gradually cover the top of the head to sharply contrast their bright white plumage. The royal tern’s most recognizable feature is their long, tangerine-colored, daggerlike bill. They utilize their sharp, vibrant bills like tweezers to pluck their prey from the surface of the water. Although, the royal tern’s size allows it to sometimes steal fish from other birds- specifically, the brown pelican!

Royal terns are most commonly found along warm, saltwater coasts where they will nest and forage near the shore. Recently, residents of the area and seasonal visitors have voiced their concerns about the heightened numbers of royal terns seen on the causeway. Many people have reached out to the Sanibel Captiva Conservation Foundation (SCCF), the City of Sanibel, and to us here at CROW in regards to the carcasses on the causeway bridge. We are entering the pre-breeding migratory season where royal terns are leaving their non-breeding grounds in South America and the Caribbean to return to their breeding grounds around coastal Florida. Royal terns have one of the longest migrations of all birds traveling on average over 21,000 miles each year.

Marine lab scientists at SCCF have detected decreased levels of the algae that blooms into red tide (brevetoxin); however, the toxin has increasingly impacted wildlife. SCCF staff covered all of Sanibel and Captiva on foot to collect data for the state-wide winter shorebird survey.

SCCF Shorebird Biologist Audrey Albrecht stated, “I would say across both islands there were several dozen, maybe close to 50 royal terns that appeared sick with possible brevetoxicosis.”

Year-to-date, there have been over 92 royal terns admitted to the Clinic for the Rehabilitation of Wildlife (CROW). Since February 1, over 60 royal terns have been admitted with 22 still in care and receiving treatment. This is a stark difference from the 49 royal tern’s admitted to CROW in all of 2020. Tests performed on deceased royal terns resulted in confirmation of high brevetoxin levels. Veterinarians at CROW have sent out several birds to the Southeastern Cooperative Wildlife Disease Study (SCWDS) to be analyzed.

CROW Medical & Research Director, Dr. Heather Barron reports, “We are currently treating the terns for brevetoxins, and several are being treated for secondary infections since they’re already immunosuppressed.”

When an animal is exposed to the brevetoxin, it can have many neurologic effects on the individual. Some early signs of brevetoxicosis (red tide poisoning) include ataxic gait, uncoordinated movements, and appearing intoxicated. These symptoms can worsen with time and more exposure. The animal can become so neurologically inappropriate that they lose their natural fear of humans and forget their natural behaviors such as preening or hunting for food.

On February 7, an adult royal tern (#21-400) was admitted to CROW from Sanibel causeway where it was found lying in the bike path and unable to stand after being hit by a car. Being hit by a car was likely secondary to brevetoxicosis or another systemic disease or infection. Upon examination, the patient was able to stand but had blood on its right wing. Radiographs confirmed there was a non-displaced radial fracture. Supportive medications were administered and the patient was placed in a body wrap to support proper healing. The patient quickly began to receive physical therapy and was reported to have a good range of motion in the right wing. The patient has since been placed on strict cage rest to be re-examined in a week and will be considered as a candidate to move outside in about four weeks.

When traveling across the causeway, slow down and keep an eye out for low-flying birds that may be landing on railings. They are likely tired and could possibly be suffering from red tide poisoning so keep in mind their coordination can be affected.

THIS WEEK AT CROW (2/12-2/18):
There were 38 new patients admitted to CROW’s Wildlife Hospital including seven double-crested cormorants, six eastern gray squirrels, four royal terns, two gopher tortoises, a black vulture, a gray catbird, three North American river otters, a red-shouldered hawk and a loggerhead sea turtle. Recent Releases include an eastern gray squirrel, a magnificent frigatebird, an anhinga, and two peninsula cooters. Check out a full list of CROW’s current patients and recent releases! Wildlife doesn’t have health insurance! Your donations help cover the costs of medical and rehabilitative care for over 5,000 patients admitted to CROW’s Wildlife Hospital each year! Want to learn more about wildlife rehabilitation? Stop by CROW’s Visitor Education Center at 3883 Sanibel Captiva Road.

About Clinic for the Rehabilitation of Wildlife (CROW)
Established in 1968, the Clinic for the Rehabilitation of Wildlife (CROW) is a teaching hospital saving the sick, injured and orphaned native and migratory wildlife of Southwest Florida and beyond.  Through state-of-the-art veterinary care, public education programs and an engaging visitor center, CROW works to improve the health of the environment, humans and our animals through wildlife medicine. For more information, or to plan your visit, go to If you find an animal that is in need of help, call (239) 472-3644 ext. #222.

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