Least Tern Life Stages In Photos

Least Tern Chick (Photos Coming Soon)

A Least Tern is born precocial which means they are born with a sort of development headstart. They have open eyes, and fluffy down feathers, and leave the nest within a few days (not flying, just wandering around within the colony). Eggs take about 19-22 days to incubate.

A Least Tern chick is ready to fly after about 19-21 days from hatching (Source: https://flshorebirdalliance.org/media/1067/nesting-timeline.pdf). Even though they can fly, they are considered fledglings and not flight-capable. Flight-capable would be when they reach the ability to plunge dive to catch fish themselves. The fledglings rely on mom and dad to hunt and deliver fish for another month or two.

The adults not only have to catch a fish, but they must find their young fledged chick within a colony that often moves around like musical chairs. The adult calls out while clenching the fish in their bill. The fledgling also squeaks out a return call. They recognize each other, and the adult plunges straight down to its chick to feed them the fish. I have also watched behavior where the adult holds the fish while the fledgling attempts to take it. I am not sure what this behavior is and perhaps it is the adult starting the teach how to forcefully grab a fish. 

As far as colors go, the downy feathers are molting away, and new brownish tinge-colored feathers are visibly growing in. The Florida Shorebird Alliance has a great aging guide located here: https://flshorebirdalliance.org/media/1058/aging-least-tern-chicks.pdf. The young juvenile almost looks more prominent (larger) than the adult. The prominent or larger appearance is because the feathers growing in through the downy feathers may make the young bird look thicker. The scalloped brown is noticeable on the crown of the head and down the back. The bill is primarily black with a little yellow, although this seems to vary. The head does not have the sharp black and triangle white of a breeding adult. However, a  strong black stripe is obvious behind the eye. The adult has a strong sharp black stripe thru the eye and meeting the bill. The stronger black helmet starts to grow in as the brown and white molts away. The juveniles will stay with the parents for approximately 3 months, according to the Audobon website here: https://www.audubon.org/gulf-restoration/least-tern

The late first-year or early second-year juvenile Least Tern has lost the brownish tinge. The bill is still black with some yellow appearing. The head feathers are molting and the sharper black helmet is getting more noticeable. The wings (primaries and secondaries) seem to have a charcoal black color instead of the gray with black tips.

Adult Least Terns in breeding plumage, have the very obvious sharp black helmet and the strong white triangle between the eyes.  The bill is now a strong orange-yellow with a black tip. The body is mostly white with light to medium gray on the backs of the wings. The wing primaries have a black leading edge. 

The adults are amazing flyers and fishers. After watching them, I consider them the best fishers on the beach as they seem to catch more fish than Ospreys. They fly over a fish-filled body of water and then hover when a small fish is spotted. They have a nickname from the past called strikers as they quickly drop out of the air and strike through the water's surface to grab a small fish. Watching them hunt is amazing. They also may have gotten that nickname from striking down on humans who have unknowingly entered their breeding territory, especially during nesting season. Unfortunately, this bird's population has plummeted over the years as with many animals, humans have taken over their habitat. Nesting in the past has occurred on beaches all over the East Coast of the United States and the Northern tip of South America. Due to nesting habitat loss from human and dog disturbances on beaches, the population has shrunk tremendously. They also had huge breeding colonies fail during the 2010 BP Deepwater Horizon oil spill. Florida has listed them as a species threatened with extinction. They are now rarely found nesting naturally on beaches and have taken up tar and gravel flat commercial rooftops. They nest in colonies which provides protection in numbers. If you watch and listen closely, you can hear when one or a few of the adult terns suspects a predator. They make an alarm call causing the entire colony to flush (fly away). They are amazing to watch and within a short time of observing them, you can see their resilience to survive.

More info can be found here: 


Least Tern Fish Exchange Mating Ritual

The Least Tern mating ritual is something extremely cool to witness. The ritual involves a male presenting and eventually handing off a fish to a female. They point their heads from side to side and do a posturing type of behavior. They do this over and over again for several minutes as if warming up. See the video above for the eventual and awkward body-bending cloacal kiss that only lasts a few seconds. Those few seconds are enough for the male to deposit sperm. 

Powered by SmugMug Owner Log In