Bermuda's endemic petrel has become a world-class success story Conservationist Dr. David Wingate has good reason to celebrate the latest successes of his cahow conservation programme, which has been making slow but steady progress since the bird was rediscovered in 1951 after 350 years of presumed extinction.

From a low of 18 nesting pairs in 1961, the number has increased to 56 in 1999. Likewise, the fledgling crop has increased from a ten-year running average of seven fledglings per year in the 1960s to 24 per year in the 1990s.

"The cahow conservation programme is one of the most successful endangered species recovery programmes on the planet at present, and its success is beginning to receive global recognition,'' an ebullient Dr. Wingate reports.

In fact, the success of the cahow and associated Nonsuch Island "living museum'' projects will be highlighted by ABC television's popular Nightline programme amid an otherwise gloomy topic of the biodiversity conservation crisis. The programme is due to air this month.

Significant progress has also been made in other areas of Mr. Wingate's painstaking conservation programme.

Of 29 chicks hatched in the 1998-9 season, 27 were successfully fledged, and the rate of new pair formations dramatically increased from four in 1998 to seven in 1999.

"Considering that the pair formation rate averaged only one new pair per year for the first 20 years of the programme, this is very significant progress,'' Dr. Wingate said.

While the number of established nesting pairs only increased by one in 1999, colonising pairs who laid eggs totals three.

Explaining the difference between "established'' and "colonising'' pairs of birds, Dr. Wingate said that the former are defined as "any pair known to have produced a first egg, whether or not that egg is successful'', while the latter are birds which have not yet laid their first egg.

"For most colonising pairs it takes from two to four years before they are mature enough to lay eggs,'' the conservationist explains. "Meanwhile, over the same time period, established pairs can be disrupted by senility or mortality. Thus, the number of new `established pairs' is never as great as the number of `colonising pairs'.'' Inevitably, success stories are tempered with failures, disappointments and set-backs, and the cahow conservation programme is no exception. Over the more than three decades of its existence, however, adversity has become a learning experience from which future mistakes are hopefully avoided.

One of the important aspects of ensuring the cahow population's survival is the monitoring of each year's fledgling crop to ensure that they have no genetic anomalies, such as wing deformities, and enough fat reserves to survive their long lives at sea.

While there were no genetic abnormalities in 1999, Dr. Wingate discovered that three of the fledglings were significantly underweight, so he had them removed to the Bermuda Aquarium, Museum & Zoo for supplementary feeding.

"As previous attempts had been successful as far back as 1972, aquarists Jennifer Gray and Patrick Talbot were keen to accept the challenge, and succeeded in making further dramatic improvements in the methodology,'' Dr.

Wingate relates.

Although one of the chicks proved too weak to survive, the conservationist describes the successful treatment of the other two as "nothing short of phenomenal'', with weight gains and other evidence of progress being carefully recorded for future reference, both in writing and on film.

On June 21, after just one week of tender loving care by the aquarists, one of the now-healthy fledglings was returned to its original nest site, from which a clearly delighted Dr. Wingate watched it come out at dark to exercise.

"It flew off as strongly as any fledgling I have ever watched,'' he remembers.

Unfortunately, returning the second chick to its burrow 11 days later ended in tragedy.

"It should have fared the same as the first chick, except for one horrible oversight that we failed to anticipate,'' Dr. Wingate confesses. "July 2 happened to be an exceptionally hot and calm day, and when we returned at nightfall to watch it exercise, we found it dead of heatstroke.'' From this unfortunate event however, a valuable lesson has been learned, and a key turned on a past mystery.

"In retrospect, we are now aware that steadily rising summer ground temperatures within the cahow burrows become lethal by the end of June, which is usually well after the normal fledgling period ends,'' Dr. Wingate explains.

"With global warming bringing summer conditions almost a week earlier on average, I suspect that heat stress has become a contributory cause to late-season chick failures in recent years. Now that we are aware of the problem, it should be easy enough to monitor temperatures and take action to prevent it, such as shade protection when conditions warrant in the future.'' The cahow conservation programme consists of four major activities: Close monitoring of the breeding islets to ensure protection against human disturbance or colonisation and predation by rats or other potential predators.

Protection of nest sites against competition from the "longtail'' or White-tailed Tropicbird (which, at the time of the cahow's rediscovery, was preventing breeding success in two-thirds of its nesting sites).

Providing additional nest sites in the form of artifically constructed burrows to meet the cahow's exact requirements for a burrow so deep and/or curved that light cannot reach the end of it.

"It is these artificial burrows, constructed where they are most needed, and most likely to be colonised, that have enabled the nesting population to increase on the small islands where the relic populations survived,'' says Dr.

Wingate.

Protection and preparation of larger islands with adequate soil coverage for burrowing, such as Nonsuch Island, so that the expanding population can eventually colonise them safely, and be in a position once again to dig their own nesting burrows as they did on the main islands of pre-settlement Bermuda.

"The living museum project on Nonsuch began in 1962 with this limited goal, but has since been broadened into a holistic restoration experiment for all of Bermuda's pre-settlement flora and fauna,'' Dr. Wingate explains.

Tender loving care: Conservationist Dr. David Wingate's long-term dedication to the dramtic comeback of the Bermuda petrel, or cahow, previously believed to have been extinct for 350 years, was captured by US artist Ted Lewin (above) in this illustration from the 1981 book, "Bermuda Petrel, The Bird That Would Not Die,'' by Francine Jacobs. (Below) This petrel was in good hands at the Bermuda Aquarium, Museum and Zoo.