This attractive member of the heron tribe is indeed partly nocturnal in its habits, but can be seen during the day, particularly at migration times when small parties or larger flocks can be seen moving between their breeding grounds and wintering quarters in Africa. During the day they roost colonially in dense vegetation and leafy trees near freshwater features, flying out to their feeding grounds at dusk where they establish individual territories. These sites can be many kilometres away from the colony. The total population in Portugal is probably less than three hundred pairs and, in the Algarve, the only confirmed breeding site is at Ludo. But worldwide, the species is common, also occurring throughout the tropics in the Americas and Asia.
Both adults share the largely grey, black and white plumage pictured, but the young birds are brown, heavily spotted buff-white and with dark streaks. Unlike the larger herons, they are stocky birds with heavy bills and short legs and are slightly smaller than the familiar Cattle Egret. In flight the wings are broad and rounded, making the juveniles look rather owl-like. A single croaking note is frequently uttered during their nightly excursions.
Migrants begin returning to their European breeding sites in mid-March. Those coming north from West Africa are vulnerable to nocturnal displacement over the Atlantic by the north-easterly ‘trade winds’ and I saw several flocks on Santa Maria in the Azores at this season.
Night Herons often nest in mixed colonies with other heron species, egrets and glossy ibis but even here they tend to form discrete groups in the upper canopy of trees. They are only locally distributed as breeders in Portugal and the best place to see them is Lisbon! Unusually, there is a long-established and flourishing resident population based on the Zoological Gardens. During the day, enterprising birds may be seen helping themselves to food left out for captive species. At dusk they can sometimes be seen in and over the city centre.
In their more natural environment, Night Herons feed mainly on amphibians, fish and insects taken from the water’s edge, but they are capable of snatching prey whilst hovering and have even been seen diving.