João Preto / Black Soul Bulweria bulwerii

Small, entirely black in color and with nocturnal habits, João-preto is one of the most difficult species of seabirds to study and where more information is lacking regarding its ecology.

  • Estatuto de conservação
    Conservation status

    Little Worrying

  • Habitat
    Habitat

    Marine

  • Distribuição
    Distribution

    Fogo Island and Branco, Raso and Cima islets. It is likely to have a wider distribution in the archipelago, although it is still awaiting confirmation.

  • Tamanho
    Size

    Length 25-29 cm; Wings 63-73 cm

  • Peso
    Weight

    75-139 g

Species rarely seen from land, it is much more common to observe it in passing, when in boats on the high seas, gliding over the water surface. As a colonial species, unlike other members of his family, the João-preto does not dig his nest and prefers to use natural cavities between stones or under vegetation, nests made by other species, or even artificial ones. The pairs, faithful to their partner, in Cape Verde reproduce from April to September, laying only one egg per year that both incubate and, later, take care of the young. The egg is laid in early June, hatches in mid-July and the chick leaves the nest in mid-September. The call of this species, exclusively made when in the nest, is very characteristic and resembles the barking of a dog. It feeds mainly on fish and squid, although crustaceans and small invertebrates comprise a small proportion of its diet.

The threats to João-preto are mainly related to the mortality associated with the accidental capture by longlines of the fishing activity, the predation by introduced mammals (rats, rats, cats) and terrestrial birds (ex: raven) and the destruction and loss habitat of nesting zones.

Curiosity: James Bulwer, a Scottish priest and naturalist amateur, in 1828 first discovered this species in the Portuguese Desert Islands, giving rise to the English name of Bulwer's petrel.

The work of the Biosphere

Little is known about their reproductive biology, namely on the brooding behavior, incubation periods and growth patterns of the offspring. There are no subspecies described for João-preto, although reproductive phenology is divergent between the colonies of Cape Verde, with reproduction on the islet of Cima (Sotavento) starting about two months earlier than on the islet Raso (Barlavento). In partnership with the University of Coimbra (MARE-UC), several studies have been carried out since 2013 to fill this information gap, especially with regard to its population size in the Raso islet, reproductive biology, food ecology, distribution and identification of threats to the species.

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