Seabirds Nest on Offshore Islands to Avoid Predators

Red-billed Tropicbird at Carvel Rock

 

When tropicbirds and other seabirds are not nesting, they mostly stay out at sea, so you aren’t likely to see them unless you, too, are out on the water. And you probably need a boat to see them even when they are settled down and nesting. 

 

When I put together a book of photos of St. John birds, Looking for Birds on St. John, a few people (mostly sailors) asked why tropicbirds weren’t included. I explained that I was generally birding on land and had never seen a tropicbird. To me, tales of these high-flying white birds with long ribbon tails seemed fantastical. But then I got excited about trying to actually see one for myself.   

Red-billed Tropicbird

In 2024, as a Christmas treat, one of my sons rented a small boat (actually a Zodiak, a larger version of a dinghy) and captained our family around St. John. I had heard that some of the seabirds nest out on the back side of Congo Cay, off the north shore of St. John, so I asked to head out there first. Unfortunately the water was very rough when we got there, with swells from the north breaking against the cliffs and then quickly rushing back out to whack us from the other side. I was afraid we would capsize, and I would find myself dragged underwater by my heavy camera and telephoto lens. Anyway there was no way I could focus my camera with the boat lurching so heavily. Disappointed, I asked my son to turn around. 

 

We decided to go along the south shore of St. John instead and had a lovely day snorkeling. I looked for nests on the high cliffs by Ditliff Point and Ram Head, and deduced from telltale white poop stains that some birds had spent substantial amounts of time on those rocks. We didn’t actually see any birds there as we went by though.    

  

This past Christmas my son took us out again, and the water was somewhat calmer on the north shore. But again, it was too rough behind Congo. Then towards the end of the day, as we were returning to town along the north shore, he swung by Carvel Rock, which is just off the east end of Congo, and suddenly called out “There it is!” 

 

An unmistakable tropicbird was fluttering its long tail feathers above the top of a craggy cliff on Carvel Rock.  

Red-billed Tropicbird

 

After hovering for a while, the bird approached the rocks.   

 

Then it settled down on a rock shelf that seemed to be serving as a nest. 

 

When the tropicbird flew up again, I couldn’t see any sign of nesting materials on the ledge, or an egg or a chick. But we were looking up from the water and didn’t have a good view into the back of the cliff. 

 

I read later that a female red-billed tropicbird usually only produces one egg at a time, and just lays it directly on the rocks, cradled in a cavity or crevice. Then both parents help incubate it, for about a month and a half. Once it hatches, the chick stays in place for about three months until it is ready to fly. So if all goes well, there will still be some tropicbird activity at Carvel Rock for a while yet. Their peak period for nesting in this area is between December and March. However, a red-billed tropicbird pair might breed almost any time during the year, depending on water temperatures and availability of fish. (Cooler water generally means more fish.)

 

Meanwhile, the V.I. Audubon Society’s volunteers from Lovango Cay for the annual Christmas bird count, Dan Boyd and Fiona Russell, reported seeing two white-tailed tropicbirds while they were out scanning for seabirds from their boat. And also a red-billed one. Both types are known to nest in this area. So now I have a new mission: to see a white-tailed tropicbird too. They have lighter colored bills – more yellow or light orange – and black lines of feathers along their backs. 

 

Nesting on a remote island helps protect a bird’s eggs and chicks from being eaten by a foraging rat, cat, dog, crab or mongoose, or even another bird, like a pearly-eyed thrasher or a hawk. Plus it’s harder for people to come out and collect the eggs for food.

 

The nests are also less likely to be trampled, by people or goats. 

Goat climbing on a cliff on Lovango Cay

On the small offshore islands, rats that swim over to look for food seem to be causing the most problems. The V.I. Audubon Society has been collaborating with the Friends of the V.I. National Park, and park managers, to support a study of invasive predators on some of the cays within the park boundaries. A recent survey conducted by an Island Conservation team indicated that black rats are present on most of the small islands in the park. Implementing a plan for eradicating the rats would be an important step towards protecting the nesting seabirds.   

 

Carvel Rock already seems like a pretty secure place. Located just outside the VI National Park, it looms up in the water like a fortress.

Carvel Rock

 

There is no beach or space to land a boat, and the cliffs rise sharply from the water. Still, I have heard that people sometimes climb the cliffs to jump off. And I suppose a hungry, determined rat could swim over from Congo to explore new territory.  

Cliff edge at Carvel Rock

 

I was surprised to see that an intrepid tree had taken root in a crack in the rock face. I asked St. John’s local tree expert, Eleanor Gibney, about it and she said it was a native fig (Ficus citrifolia) that had been growing out there for over 50 years. I imagined a bird flying over there after eating a tasty fig, setting down, and then depositing a seed in its poop.    

 

I didn’t see many other signs of life on Carvel that day. There was one other bird, a brown booby, which seemed to just be taking a rest on the rock. These common seabirds are easily visible from the shoreline, or flying beside the ferries, but they make their nests away from people on offshore islands, usually gathering together in groups.   

 

Brown Booby at Carvel Rock

Last May, on a V.I. Audubon Society boat ride, I did see a few bridled terns nesting high up on Carvel Rock. Like tropicbirds, these are seabirds that rarely come close to shore. 

Bridled Terns nesting at Carvel Rock in May 2025

The idea of hiding out on an isolated island fortress can seem fairly appealing these days. Yet even though nesting birds are able to engage in some protective behaviors, they clearly have only limited defenses against predator invasions, climate change, more violent storms and habitat loss. Just like us. Except that hopefully we have a bit more capacity to anticipate, and avert, foreseeable dangers. 

 

Partying with Flamingos

Like people, flamingos enjoy getting together in groups and socializing. And this year we have been blessed with amazing gatherings in some of St. John’s ponds – the annual December bird count included over 100 flamingos. Wow!

 

A couple of years ago we were delighted to report just one flamingo that showed up on the south shore, so these flashy birds are providing a dramatic new bird watching attraction on St. John.   

 

Historically, flamingos were native residents of the Virgin Islands, but then early European settlers found them to be good eating – ‘tastes like a goose’. Their honking voices do make them sound a lot like geese. But of course they are so much more beautiful. Anyway, between hunting, feather gathering and habitat loss, they were all wiped out by the mid-1900s. 

 

Then in 1992 a conservation group reintroduced a small group of flamingos from Bermuda to the British Virgin Islands. Those birds successfully reproduced, and there are now hundreds of flamingos on Anegada, the farthest north island in the BVIs. Another group was later brought to Necker Island. With growing populations in the BVIs, it seems that some of the flamingos have now decided to spread out and are flying over to check out the living conditions on St. John.

 

I have been lucky enough to spend time with some flamingos having rather noisy parties. I wasn’t actually invited, but they were gracious enough to allow me to sit quietly on the sidelines with my camera. 

 

Sometimes the flamingos seem to be enjoying quiet conversations. 

 

 

Later there might be dancing.

Underneath the wings, the flamingo feathers are black, not pink.

 

And sometimes it looks like they are kissing.

 

Perhaps an embrace. Or a power move?

 

Then, all of a sudden, one of them might take offense and deliver a quick bite.  

 

Which might lead to some chasing.

Many of the flamingos in St. John now seem to be adults, judging from their size and coloring. But I noticed a few small, white ones that looked quite young. I am wondering if they might have been born on St. John over the summer, but can’t be sure. A baby flamingo grows almost to full size within a few months, and can fly soon after that, so possibly the young ones flew over to St. John with their parents. 

 

It can take a couple of years for the young flamingos to get their distinctive pink look. As they grow up they have to consume lots of red-orange carotenoid pigments (like the ones that color carrots and tomatoes). The flamingos get those pigments by eating microscopic algae in the water, and crustaceans like brine shrimp that also eat the algae. The pigments are broken down in their digestive systems and then get deposited in their feathers and skin. 

 

Members of a group of flamingos can vary quite a bit in coloring depending on their age and diet. Male flamingos are usually a bit larger and heavier, but not necessarily a darker color than females.

 

The feeding process involves the flamingos holding their heads underwater, shuffling their feet to stir up the mud on the bottom, sucking in mouthfuls of water, using their tongues to push out the water and strain it through comb-like filtering structures inside their beaks, and then swallowing anything edible. 

 

Besides algae and brine shrimp, they also pick up other small crustaceans and invertebrates, insect larvae, and some seeds and other plant material. They are able to tolerate feeding in very salty ponds where other birds don’t go because they have special glands that they can use to excrete salt through their nostrils. 

 

And when the partying is over, it’s time to rest and give thanks for the blessing of a day with flamingos. 

A Scarlet Ibis Family in the Fish Bay Pond on St. John!

 

There’s a juvenile scarlet ibis that was born here! Now almost as big as its parents. 

And there may be more wandering around. My neighbors recently saw three babies in the pond with the parents. But I have only seen one young one since I returned a few weeks ago. 

What a thrill to see these birds up close. For six seasons my husband and I watched the one lonely ibis in Fish Bay, hoping that an appropriate mate would come. Based on previous photographs, I think the bird on the left is the resident male. His feathers are now looking a bit uneven in color, but that is probably due to molting, which usually happens after breeding season.  

I think the newcomer is the female, and a younger bird because of her not-fully-developed purplish neck feathers. The male and female adults have similarly colored feathers, but they don’t reach their full adult plumage for a few years. Their color comes from carotenoid pigments contained in the food they consume, including small crabs, shrimps and other invertebrates, as well as some types of seeds and insects. They use their long bills, which have sensitive tips, to probe in the mud for food.  

I heard reports of other ibises coming over to Fish Bay the summer before this. (They have all probably come from the flock introduced by Richard Branson on Necker Island in the British Virgin Islands.) However, there was only one ibis in the pond when we returned last fall. And the resident ibis continued to consort with a snowy egret, which had become a faithful companion, year after year.

Interestingly, the snowy egret is still there, now apparently as a family friend. And sometimes a very large yellow-crowned night heron also seems to be standing guard. 

 

A great egret has also taken an interest in the youngster. 

As well as a green heron that monitors all the activity on the pond. 

And a black-necked stilt insisted on being included in a family portrait.

The trees along the road have grown up so much it is hard to see into the pond now. The birds tend to stay far back in a corner by the big tree stump. To get a view of them my husband and I had to crawl down off the side of the road and creep along through the bushes into the mangroves along the edge of the pond. Lots of rain has made the ground soft and muddy, and to my dismay, one morning I ended up sliding down into the slimy mud on my butt. Fortunately I was able to keep my telephoto lens safe, and later went back with dry pants. 

We have mostly seen the ibises between 6:30 and 8:00 am. After that they usually disappear into the bush or fly off. However, there are many other birds using the pond throughout the day. Besides the ibises, egrets, stilts and green herons, we also saw little blue herons, lesser yellowlegs, spotted sandpipers and clapper rails.  

We recently learned that the Fish Bay conservation land, which includes this pond, has been bought by the V.I. government with a grant from the National Oceanic and Atmospheric Administration (NOAA). It is to be held as a nature preserve by the V.I. Department of Planning and Natural Resource in a new Division of Territorial Parks and Protected Areas. The ownership of this area was in limbo for a number of years during which the land has been mostly untouched, except by the hurricanes. 

It will be wonderful for this new nature preserve status to ensure long-term protection for all the wild birds and other creatures living in the wetlands here. It would also be good to provide a low impact viewing space that will allow people to observe what’s going on in the pond without disturbing the wildlife. The platform on St. John at Frank Bay built by the V.I. Audubon Society could be a good model. 

The wetlands currently offer safe nesting spaces for a variety of birds. I was interested to see that both the scarlet ibis parents seemed to be taking care of the young one. I read that because of their long bills the newborn babies need help holding their heads up to get fed, so the feeding process requires two parents.  

The baby scarlet ibises are grey. Then they soon start growing pink wing feathers, along with black feathers for their wing tips. My husband refers to this one as ‘splotchy’. 

The young ibis occasionally keeps company with a chatty black-necked stilt instead of the parents.  

Possibly after a while the parents start to seem overbearing.

One day the scarlet ibis youngster may fly off to pursue its own adventures. But for now it is a welcome addition to the Fish Bay neighborhood. 

Green Heron Observations

Green herons sit patiently and watch intently.  

Instead of thrashing around in the pond, sometimes it is better to just be still and quiet, waiting for an opportunity to arise. Like a fish swimming by. And then be ready to spring into action.

A green heron can move quickly and decisively when the time is right.

 

Green herons are also famous for using tools - dropping leaves or bugs into the water to attract fish, then picking up and repositioning the bait as needed. Very smart. I have only seen videos of this, though. Maybe the green herons I’ve watched have had plenty of fish and didn’t need to work that hard. 

 

Sometimes patience is all you need to catch a big fish.

Often people make up names that are meant to be descriptive but don’t really fit. There aren’t really many green feathers on a ‘green’ heron. To me their back and head feathers look more blue, and their necks are rusty red.

 

Those necks You can see better if you stick your neck out. 

And it can be convenient to just lean down and suck up a fish for dinner. 

But sometimes it’s good to blend into the background. Rusty striped neck and chest feathers can provide camouflage when the green herons are lurking by the edge of a pond.  

There are green herons that live in the Virgin Islands all year, and a few others that come down for the winter. The permanent residents live in the wetlands and make nests out of sticks, either on the ground or in trees. 

Usually the green herons keep their nests pretty well hidden. However, Laurel Brannick recently saw one with a nest in plain view, hanging out on a branch over the Francis Bay pond on St. John. 

Photo Laurel Brannick

The exposed location was probably not the best choice. Laurel thought she saw two chicks in the nest, but by the next week the nest was empty.  

Why Don’t Hermit Crabs Make Their Own Shells?

 

Hermit crabs have hard claws and legs, but soft abdomens they stick inside abandoned mollusk shells.

I enjoy having hermit crabs in the yard. They are known as soldier crabs in the Virgin Islands, but are not aggressive. They are generally cute and fun, and come by to snack on leftover cat food. 

Cats may not be so happy to see these intruders. But even if they catch a snacking hermit crab red-handed, they can’t do much damage to it when it's drawn up inside its shell. The hermit crab can stay inside its shell until the cat gets bored and leaves.  

 

Even when hermit crabs hide inside their shells, though, their legs and claws usually stick out some. As they grow larger, their legs and claws hang out further, and they have to start searching for a bigger shell.  

 

Recently I started to wonder why, after over 150 million years, hermit crabs are still scrounging around for discarded mollusk shells to cover their butts. 

 

Caribbean hermit crabs, or soldier crabs, (Coenobita clypeatus) commonly use cast-offs from West Indian Top Shells (Cittarium pica), otherwise known as whelks or wilks.

They are called ‘top shells’ because they resemble small spinning toys. 

 

West Indian Top Shells, like other marine snails, build an exterior exoskeleton through a process called biomineralization. They have an organ called a mantle that secretes a thin layer of protein as a base, followed by layers of calcium carbonate, which they create using carbon and calcium ions drawn from the seawater. The calcium carbonate then solidifies to make the hard shell. Later on, the mantle can add to the edge of the shell, so the same shell can grow as the snail gets bigger. 

Most crabs also use calcium carbonate to make hard shells for themselves that cover their whole bodies. But their shells are fitted to their legs and bodies, and not expandable. In a process called molting, as the crab grows bigger, it forms a new, thin exoskeleton cover underneath the existing shell, and breaks out of the old one. Once out, the crab then quickly makes the new, soft exoskeleton harder using calcium carbonate.    

 

Hermit crabs do the same kind of growing and molting as other crabs, but only their claws and legs get hardened up. The abdomen stays soft and the hermit crab needs to find a new larger shell to cover it. The shells provide protection from predators and also prevent them from getting dried out and cooking in the tropical sun. 

They do briefly take their shells off to mate. A male hermit crab will tap on a female’s legs to persuade her to come out and mate.   

 

Female hermit crabs make a group pilgrimage down to the shoreline to deposit their eggs in the water. There the eggs go through several free-floating phases of development before the baby hermit crabs start their transition to land. While in the water, they need to locate a discarded shell from a (dead) micro-mollusk, which are species of snails that remain tiny even as adults. Over time they will then work their way onto land and into ever larger shells.

Depending on finding abandoned shells from other dead animals seems pretty iffy as a life strategy, although it does allow successful hermit crabs to avoid spending a lot of energy building and maintaining their own mobile homes. They are renters, not owners, which in some situations can be an advantage. 

 

Still, the hermit crabs are heavily dependent on continued housing availability. There needs to be a large population of whelks – and intact shells left behind after they die or get eaten. In the Caribbean, an octopus or lobster will eat whelks, as well as bonefish, porcupinefish, and rock hinds. The whelks are also attractive to shorebirds like oystercatchers, which are locally known as whelk-crackers. And then there a number of people who collect whelks for stew. Supplies of whole, empty shells can quickly become limited. 

 

Hermit crabs are essentially recyclers, taking cast-off resources and reusing them, and in the process cleaning up the beaches. If they can’t find a shell that fits, they will sometimes end up wearing beach trash instead, which is a bit sad to see, but adaptive and enterprising of them. 

 

A hermit crab’s survival plan is also a bit poetic, as each temporary shelter it finds will carry a history of prior lives, which it will carry on its back, and then pass along.

 

 Small hermit crabs use shells other than top shells.