Seabirds Nest on Offshore Islands to Avoid Predators
VI Source | By Gail Karlsson | January 24, 2026 | 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, 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.
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.
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.
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.
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.
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.
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.
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.
Gail Karlsson is the author of a photo book Looking for Birds on St. John, as well as two other books about nature in the Virgin Islands –The Wild Life in an Island House, and Learning About Trees and Plants – A Project of the Unitarian Universalist Fellowship of St. John. Follow her on Instagram @gailkarlsson and gvkarlsson.blogspot.com. More info at gailkarlsson.com
Photo: A red-billed tropicbird hovered over Carvel Rock. (Photo Gail Karlsson)
