The least tern (Sternula antillarum) is the smallest species of tern in Florida. It is protected under the Endangered Species Act and the Migratory Bird Treaty Act due to population declines caused by habitat loss and disturbance. The Florida Fish and Wildlife Conservation Commission (FWC) manages and protects nesting colonies of least terns along Florida’s coasts.
What is a least tern?
The least tern is a small, graceful seabird in the family Laridae. It measures around 9 inches in length and has a wingspan of 20 inches. Least terns have pearl gray upperparts, snowy white underparts, a black cap on the head, yellow bill, and yellow legs. Their tail is deeply forked and their wings are long and pointed.
Least terns nest in colonies on open, sandy beaches or flats along the coast. They lay their eggs in shallow depressions in the sand or shell material. Their diet consists mostly of small fish and invertebrates like shrimp and crabs. Least terns plunge dive for prey in shallow water or pick insects and small fish from the water’s surface while flying. They have a high-pitched, sharp “keey” call.
Why are least terns endangered?
There are several reasons why least tern populations have declined over the past century, leading to their protection under the Endangered Species Act:
- Habitat loss – Development of coastal areas for human use has destroyed and degraded least tern nesting and feeding habitat.
- Disturbance – Beachgoers, vehicles, pets, etc. can disturb nesting colonies, causing nest abandonment and chick mortality.
- Predation – Predators like gulls, racoons, and foxes prey on eggs and chicks.
- Storm events – Hurricanes and storms can wipe out entire colonies by flooding nests.
Least tern population trends in Florida
Historically, least terns nested along the entire coastline of Florida. Over the last century, the least tern population in Florida declined significantly due to habitat loss and disturbance:
- In the 1920s, estimated 20,000+ nesting pairs in Florida
- By 1960s, population dropped to about 1,500 pairs
- In 1973, least tern was listed as threatened in Florida
- In 1987, listed as federally endangered
Thanks to conservation efforts, the least tern population in Florida has rebounded substantially since listing. In 2019, there were over 7,000 nesting pairs across the state. Some of the largest colonies are found along the Gulf Coast from Franklin County to Collier County.
Least tern nesting habitat
Least terns nest on barren to sparsely vegetated sites near water, including:
- Sandy beaches
- Shell/gravel bars
- Islands
- Spoil islands
- Salt flats
- Dredge material sites
Ideal nesting habitat has these characteristics:
- Open terrain with good visibility to watch for predators
- Lack of vegetation or very sparse vegetation
- Close proximity to feeding areas with shallow water
- Minimal human disturbance
Nesting season
In Florida, least terns arrive at breeding colonies in April and May. The nesting season runs from May through August. Here is an overview of the nesting timeline:
- Courtship and pairing – April – May
- Nest building – May – June
- Egg laying – 2 eggs per nest, early May – mid July
- Incubation – Both parents incubate; lasts 20-25 days
- Hatching – Late May – August
- Chick rearing – Both parents feed chicks; fledge at age 3-4 weeks
- Fledging – June – August
Nesting colonies are extremely sensitive to disturbance during the breeding season. Care must be taken to avoid disturbing incubating or brooding adults, chicks, and fledglings.
Threats to nesting least terns
Some of the major threats to nesting least terns in Florida include:
- Human disturbance – Recreational beach use, vehicles, unleashed pets, fireworks displays, etc.
- Habitat loss – Coastal development, erosion, vegetation overgrowth
- Predators – Gulls, foxes, raccoons, ghost crabs, fire ants
- Storm events – Hurricanes, tropical storms
- Sea level rise – Reduction in nesting habitat
FWC conservation efforts
The FWC coordinates statewide conservation efforts to protect and recover the least tern. Some FWC programs include:
- Annual statewide survey to monitor population and nesting success
- Banding program to track individual terns
- Predator control at nesting sites
- Public outreach and education
- Habitat management, including vegetation control and placing shell/gravel
- Nest enclosures or exclosures to protect against predators
- Law enforcement presence at nesting beaches
- Coordinating with partners like Audubon Florida and U.S. Fish and Wildlife Service
Public cooperation needed
The FWC emphasizes that public cooperation is critical for the conservation of least terns in Florida. Here are some ways the public can help protect nesting least terns:
- Avoid entering posted nesting areas
- Leash pets at beaches during nesting season
- Don’t fly kites or drones near nesting sites
- Take down beach equipment at night so it can’t attract predators
- Pick up trash that may attract predators
- Fill in holes dug in the sand after your beach day
- Report disturbances or predators to FWC
Interesting facts about least terns
- They are monogamous and mate for life. Pairs reunite at the same nesting site each year.
- If a mate doesn’t return, the remaining bird will find a new mate.
- Their legs and feet are yellow-orange, leading to the nickname “yellowlegs.”
- Least terns hover and then plunge-dive feet first to catch fish.
- They fly with fast, stiff wing beats and look mostly white below with dark outer wing edges.
- Groups of terns making high “keey” calls while flying are called “commuters.”
- Least tern chicks can walk and swim within hours after hatching.
- The oldest banded least tern was over 17 years old.
Conclusion
In conclusion, the least tern is the smallest member of the tern family nesting along Florida’s coasts. Habitat loss and disturbance caused significant declines in the 20th century, leading to Endangered Species Act protection. Thanks to conservation efforts by agencies like the FWC, least tern numbers in Florida have rebounded while still facing threats. Protection of nesting habitat and public cooperation in avoiding disturbance are key to the continued recovery of these special seabirds.