Known locally in Guadeloupe as “Diable,” the Black-capped Petrel previously was wide-spread on the highest peaks, most importantly in and around the Soufriere volcano. French naturalist Pere Labat, while in Guadeloupe from 1693-1705, wrote in his journal about Black-capped Petrels on the steep slopes of the Soufriere volcano. Scientists believe that as humans developed Guadeloupe and trees were removed and invasive exotic mammals were introduced, Diable retreated to the steepest slopes of Soufriere. By the 1800s, it was thought that the only breeding location remaining was near Nez Casse, which is on the north slopes of Soufriere. This is in part because the species was last recorded at this location in 1847. Then in 2004, numerous Black-capped Petrels were observed offshore of Guadeloupe. A few years later, two staff with the Parc National de la Guadeloupe thought they heard and saw two Diable as they flew over from the coast towards Soufriere during early morning wildlife surveys inland near Col des Mamelle.

In 2020, EPIC in partnership with AMAZONA and the Parc National de la Guadeloupe, conducted an expedition using radar and night vision scopes to look for Black-capped Petrels. EPIC team leader Adam Brown has pioneered the use of marine radar in the Caribbean over the past decade. This technique included shipping the radar equipment to Guadeloupe, loading it onto a vehicle and climbing steep dirt roads to an ideal vantage point on the mountainside; the researchers then wait until dark and, while watching a computer screen, classify radar targets by size and speed to determine the possibility that it is a Black-capped Petrel. The night vision scopes provide the team with additional eyes to verify these targets. The team did indeed see petrel-like targets with radar below the slopes of both Nez Casse and Soufriere, thus providing evidence that a small local population of the species may persist on Guadeloupe.

Future expeditions would include additional radar surveys followed by daytime searches for possible Black-capped Petrel nesting burrows. The search for nests includes hiking and mountain climbing and the use of an endoscope to look in the nest burrows, which may be up to nine feet deep in the side of cliff.