Bermuda’s critically endangered Cahow population has continued to grow thanks to the work of dedicated conservationists.

According to the 2012/13 Cahow Recovery Programme Report, by the Department of Conservation Services, a total of 105 nesting pairs returned to the Island — almost certainly the most since the early 1600s.

And while the nesting programme on Nonsuch Island continues to develop, researchers were surprised to discover the birds had naturally begun to colonise the nearby Southampton Island to the southwest of Nonsuch.

“Southampton Island has been highlighted as a potential future site for a breeding colony of Cahows several times during the course of the present Recovery Programme,” the report stated.

“A small number of Cahows may have survived on Southampton Island as late as the 1940s to 1950s, as Dr David Wingate recalls finding Cahow remains, probably rat-predated and still fresh enough for some tissues to remain on the bones.

“The first evidence that something unusual might be happening came to light on August 6, 2012, when the carcass of a nearly fully-fledged Cahow chick was found on top of Southampton Island.”

A search of the Island revealed three pairs had nested in deep rock crevices near the northern end of the Island, and one of the three nests had successfully produced a fledgling.

Cahows thrived in Bermuda before the Island was colonised by man, but the animals were quickly targeted by colonists as a food source and further devastated by the introduction of new predators including rats, cats and dogs. The species were believed to be extinct by the 1620s, but they were rediscovered in 1951 when conservationists found 18 nesting pairs on the rocky islets of Castle Harbour.

Since then, the species have been the subject of a dedicated conservation effort to bring the birds back from the brink of extinction, including the restoration of Nonsuch Island to provide a new, suitable nesting ground.

As part of the efforts to expand the Cahow population on Nonsuch Island, the Department translocated 14 fledglings from Long Rock, Horn Rock and Green Island to produce a second colony. While the majority of translocated fledglings successfully took flight from Nonsuch Island, the report stated two of the birds died as a result of spoiled food.

“Upon investigation, it became obvious that the cause of death of both chicks was due to being fed food that had spoiled due to another major project going on at Nonsuch Island during the same time as the translocation project,” the report stated.

“Due to the large numbers of workers and volunteers on the island during the installation of the new Solar Power System for the Island, many were storing their lunches and drinks in the refrigerator at Nonsuch House. As a result, the refrigerator door was being opened constantly over a one-week period, resulting in the food thawing out slightly in the warm temperatures at that time.

“Past experience has already shown that petrel chicks are extremely sensitive to bacterial contamination in spoiled food, and a total of five Cahow chicks became sick due to eating this batch of food. Three of these chicks were able to be nursed back to health; however two of the lightest birds could not be saved, having regurgitated all food that was attempted to be fed to them.”

The population also faced another challenge last November when a predator believed to be a Great Horned Owl killed two or three Cahows. The owl however remained on the Island for a few days before leaving Bermuda.

Despite the difficulties, a total of 53 chicks fledged on the Island during the 2012/13 season.