Rombo, Branco, Raso and Rabo-de-junco (Sal) islets of Birds and Curral Velho (Boavista). Santo Antão, São Nicolau, Santiago and Maio Islands. Probable nesting in Santa Luzia.
Length 19-21 cm; Wingspan 43-46 cm (from H. castro, similar species)
Preferring to nest in holes in cliffs or under rocks, the preferred habitat of their colonies are always close to the coastline, normally associated with other species of seabirds. Eating during the day and returning to the nest at dusk, it is common to hear calls in flight near the colony, or even from inside the nest that remains well hidden. Outside the breeding period, Pedreirinho, like other species of seabirds, is pelagic and migratory, only coming to land to nest, but is present in the waters of Cape Verde throughout the year. Evidence (eg bird calls) suggests that it breeds on 10 islands of Cape Verde, although only half of them have confirmed nesting, and their reproductive phenology is currently being studied. This species prefers to feed on planktonic crustaceans, small fish and squid.
Local threats are mainly due to the introduction of non-native predators. Cats, rats and rats are the potential responsible for the decline of its population in Cape Verde, the largest colonies being maintained only because they are in places inaccessible to this type of predators.
Curiosity: Its behavior is so elusive that in order not to be preyed on land, Pedreirinho is known for avoiding visiting the colony on nights of full moon. Morphologically, the Hydrobates castro and Hydrobates jabejabe they are impossible to distinguish. The separation into two distinct species was made only because there were divergences in song and genetic evidence that justified the taxonomic recognition of a new species.
The work of the Biosphere
Given the discreet behavior and the remote and difficult to access nesting areas, the population estimates are out of date and / or uncertain. Like João-preto, little is known about his reproductive biology, food ecology and distribution. Several researchers from the University of Coimbra (MARE-UC) have been working since 2013 to collect more information about this breeding species in the Raso islet.