Bermuda seems to be a favorite destination for lost and vagrant seabirds, which is not surprising when you consider its solitary location as the only oceanic island in the Northwest Atlantic between the Caribbean and Nova Scotia. The nearest landmass is Cape Hatteras in North Carolina, located almost 600 miles to the west-northwest. Recently, Roseate Terns have started to re-nest on Bermuda for the first time since the 1830s, and we have been watching with interest for several years the attempts of “Stormy”, a Leaches Storm-petrel, to attract a mate to at least 2 separate nest burrows at the recently re-established Cahow nesting colony on the Nonsuch Island Nature Reserve. This is despite the fact that the nearest nesting colonies of Leaches Storm-petrel are 800 miles away on islands off the coasts of Maine and Nova Scotia.
An even more improbable record has now occurred, with a dark-morph Trindade Petrel (Pterodroma arminjoniana), which is in the same genus as Bermuda’s own endemic Bermuda Petrel or Cahow (Pterodroma cahow) was found on the ground by Mr. Robert Cabral in a Nature Reserve area on the South Shore of Bermuda. This bird looks very similar to our Cahow, except it is all dark grey, with a larger wingspan. It occurs in both a light morph, with much lighter plumage in the belly and wings, and the dark morph. It appeared to be prospecting for a nest site under some hurricane-deposited boulders, only a few feet from a heavily used public trail, and called loudly when approached.
This trail is heavily used by the public for walking their dogs, which are often illegally let off their leashes, and there are a number of feral cats wandering in the Reserve, associated with a nearby cat feeding station. These cats have been photographed in this Reserve several times killing water birds as large as Coots and Moorhens (Gallinules), and so pose a serious threat to any ground-nesting seabirds, and to top it off there is a large population of rats living in the area.
Unlike Nonsuch Island and other offshore islands, from which mammal predators can be more easily eradicated or kept off, introduced mammal predators cannot be completely eliminated from sites on the main island of Bermuda. This situation is compounded by regular “dumping” of unwanted cats from other locations on the island, and the presence of feral cat feeding stations by well-meaning but misguided members of the public, despite the fact that these are illegal in National Parks and Nature Reserves on Bermuda.
Due to these factors, it was felt that its presence in a easily accessible ground nest placed this bird in imminent danger of predation (unlike White-tailed Tropicbirds, which nest near this area in cavities in vertical coastal cliffs not usually accessible by Cats and Dogs), and the decision was made to remove the bird and take it to the Bermuda Aquarium, Museum and Zoo.
After a brief examination and morphometric measurements by Mr. Paul Watson and myself, the bird was fitted with an identification ring (band), which will enable the bird to be positively identified should it be recaptured anywhere. The bird was found to be in good physical condition and at a good weight, and based of the feather moult sequence and the amount of filoplumes (small, hair-like structures) on the bird’s head, Mr. Watson felt that this was a relatively young bird, perhaps prospecting for a potential nest for the first time.
The decision was made to take the bird out to Nonsuch Island, where all mammal predators have been removed and where there are two breeding colonies of the related Bermuda petrel, since I felt that it best for the bird to recover in and perhaps acclimatize to a new, safer and more suitable potential nesting area. The Trindade petrel was placed into the failed “CahowCam 1” nest burrow, where the resident Cahows had departed since early April after the failure of their egg, but which still contained nest material and the distinctive musky “petrel” smell. The burrow entrance was blocked for 24 hours to enable the bird to fully recover, during which time it could be monitored with the livestream camera and its reactions noted, and it was unblocked the following day at about 3pm.
Much to my surprise, the petrel appeared to settle down immediately inside the burrow and preened itself, gave an occasional loud cry of the type that is uttered inside a nest burrow to attract mates, and created a nest scrape and re-arranged nest material. After I unblocked the entrance of the burrow the next day, the bird did not try to leave immediately as thought and stayed for the next 24 hours, continuing to act as though it was settling down inside the burrow and staying firmly inside.
It was not until Saturday afternoon, after two full days in the burrow, that the Trindade Petrel left the nest chamber after a last look back and leaving excreta to “mark” the burrow, and walked outside, where it spent several minutes looking around and getting its bearings. Finally, after spreading its wings a few times on top of the entrance to the adjacent “CahowCam 2” R832 nest burrow, the bird took off strongly straight out to sea, departing at 3.23 pm. This is in marked contrast to the cahow, which never leave their nest burrows during the light of day, being completely nocturnal on the breeding grounds. My impression was that the bird behaved similarly to how Cahow fledglings do when they imprint at night before departing to the open ocean.
What makes this all even more interesting is that this is now the third time a Trindade Petrel has been recorded near, over or on Bermuda in the last few years; a light-morph Trindade was seen several miles off the east end of Bermuda flying with Cahows by a pelagic birding group in November 2016; and only in January and February of 2019, another light-morph bird was seen flying & calling repeatedly over a residence in central Devonshire Parish, near the center of the main island of Bermuda, returning repeatedly during the afternoon over several weeks.
The Trindade Petrel only nests in the Southern Hemisphere on Trindade Island and the Martin Vaz Islands in the South Atlantic Ocean, about 1,100 kilometers (680 miles) east of the coast of Brazil, which it constitutes a part of. Trindade has a total area of 10.1 square kilometers (3.9 square miles), while the tiny Martin Vaz islets have an area of only 0.3 Square kilometers (30.0 hectares). The islands are volcanic in origin, and have rocky, mountainous terrain. The population is only 32 Brazilian Navy personnel at a Coast Guard and Research station. 85% of the island was formally covered with forest until goats were released in 1700 by Sir Edmund Halley from HMS Paramore. Other invasive alien mammals were also introduced at different times, including pigs, cats and mice, which collectively had a catastrophic effect on the island’s flora and fauna, much of which was unique to the island.
The Goats in particular massively increased in number and destroyed the forest cover, eating all foliage and stripping the bark off vegetation. The island’s trees were almost entirely eliminated, causing massive erosion of soil. Things are looking much more hopeful for the island at the present time, with pigs being eradicated from Trindade by the 1950s, the last goats by 2005, and cats by 2009. Efforts are still underway to remove the last mice, and these measures are beginning to enable restoration of the island, enabling the remaining native flora & fauna, including the Trindade Petrel, to be preserved, and enabling areas which still have some soil cover to be reforested.
It is probable that these invasive mammals have had a serious impact on the Trindade Petrel population and other seabirds nesting there, as they have on many other oceanic islands, including Bermuda. Following extensive research, the estimated population of Trindade Petrel was recently revised to 1,130 breeding pairs (compared to a total population of 131 pairs of Cahows on Bermuda). There are also several hundred pairs of Trindade Petrel nesting on Round Island in the Indian Ocean, near Mauritius.
We have no idea what the ultimate outcome of this extraordinary record will be or why these birds seem to be taking an interest in Bermuda, which is over 5,000 miles from its breeding colony, which even lies in a different hemisphere. Natural History is rarely dull, but this record is definitely one for the history books, and we will wait with great interest to see if this bird returns to possibly try and establish a foothold for the species on Bermuda, or if it is indeed a once-in a lifetime record.
Jeremy Madeiros | Principle Scientist – Terrestrial Conservation, Dept. of Environment and Natural Resources, Bermuda
Watch a LIVE view of the CahowCam 1 burrow to see if it returns.