The great cormorant is a large bird of metallic black- blue colour. It can dive underwater in search for fish. It often perches on rocks or on other roosts holding its wings half open to let them dry: in fact, it lacks the uropygial gland (a gland producing an oil secretion which spreads all over the body) and its plumage is therefore not impermeable.
It is a formidable swimmer and moves swiftly under water keeping its hooked beak upwards; when threatened, it moves keeping its body completely submerged with only the neck above the surface.
It breeds in colonies, generally in a tree. Three or four eggs are laid in spring. Offspring are born about 28 days later and leave the nest at one month of age. However, they can fly only after three more weeks.
Its flight is fast: it flies low over the water or high over dry land. The flock often lines up in a wedge or in a straight flight.

Bibliography

Svensson L., Mullarney K. & Zetterstrom D., 2013 - Guida degli uccelli d'Europa Nord Africa e Vicino Oriente. Ricca Editore.
Saporetti F. & Carabella M., 2012 – Uccelli Acquatici Svernanti – 25 anni di dati in Provincia di Varese. Quaderno 1 del Gruppo Insubrico di Ornitologia. Provincia di Varese, Settore Politiche per l'Agricoltura e Gestione Faunistica e LIPU.
Aletti R. & Carabella M., 2015 – Check-list degli Uccelli della Provincia di Varese – Lista completa commentata e illustrata. Quaderno 2 del Gruppo Insubrico di Ornitologia.

Fotografie: Isella Bellotti