Efforts to re-establish Bermuda’s national bird on Nonsuch Island have hit a new milestone this year as the cahow continues to bounce back from near extinction.

Jeremy Madeiros, a senior terrestrial conservation officer with the Nonsuch Preservation Project, said in a post on the Nonsuch Expeditions Blog that a record number of chicks hatched on Nonsuch this year.

“As of March 27, I can confirm a record number of 25 chicks on Nonsuch, significantly breaking last year's record of 19 fledged chicks, so we have finally broken the 20-chick mark,” he said.

JP Rouja, Nonsuch Expeditions founder, noted that weather challenges made it difficult to visit smaller outer islands and check on the cahow colonies there.

“We do know that there have been a few chick losses and a lower success rate on those outer islands in part due to last year's hurricanes,” he said.

“However, this is hopefully offset by the Nonsuch increase keeping us on track to match or exceed the record of 78 for the entire colony from two years ago.”

Mr Madeiros said that of the Nonsuch Island chicks, the largest was the one hatched in the burrow watched by thousands online through the CahowCam 1 livestream.

“On March 27, it had increased to 319 grams, as heavy as an adult female cahow, with a wing chord length of 55mm,” he said.

“As this chick is only one-third fledged at this point, with an eventual wing chord length of up to 275mm by the time it will be ready to fledge in about two more months, it is obvious that this chick is being well cared for by both adult birds, and I suspect it will become considerably heavier if it continues to be as well taken care of by the parents.”

While not all of the eggs laid on Nonsuch hatched, Mr Madeiros noted that there was still a fair number of adult birds recorded in nests where eggs failed.

“This is normal, as even when the egg has failed in a cahow nest, the adults will often continue to visit the nest up until the beginning of April, both to strengthen the pair bond and connection to the nest, but also to defend the nest burrow from being taken over by young adult cahows, newly returned from three to five years at sea after fledging as chicks, and looking for an empty nest burrow of their own,” he explained.

“If the resident male cahow returns to find a stranger in its nest, it will aggressively eject the stranger from the nest.

“These fights can be quite vicious, as a cahow's wicked hooked bill is quite strong and razor-sharp, as I know well, sporting a collection of scars on my hands from adults objecting to me removing them from their nests for ID band checks and measurement.”

Mr Madeiros added that he had also been able to confirm at least one new pair of cahows on Nonsuch Island, with the male having been translocated to the island colony in 2017 and the female originating from a nest on one of the small original nesting sites.

“This pair should hopefully return next year to the nest to lay their first egg together, which would bring the total number of established breeding pairs on Nonsuch up to 40,” he said.

“There is also still a week or two remaining to discover other new establishing pairs, and hopefully the weather conditions will allow us to make more visits to the nesting islands so that we can determine the total number of hatched chicks for the entire island.”

Cahows, also known as the Bermuda petrel, were largely wiped out by introduced predators and hunting by early English colonists. By the 1620s the species was believed to be extinct.

However, the species was rediscovered in 1951, with a handful of the birds found nesting on four rarely-visited rocky islets, sparking efforts to rebuild the population.

As part of the project, man-made burrows were created on Nonsuch Island with chicks translocated to the island in the hope that they would return to Nonsuch as adults.

The project has borne fruit with a growing number of birds fledging on the island and, for the first time since the 1620s, a cahow couple last year successfully dug its own burrow and raised a chick inside of it.

• For more information about Nonsuch Island and the cahow conservation effort, visitwww.nonsuchisland.com