The zigzag heron (Zebrilus undulatus ) is a species of heron in the family Ardeidae, also including egrets and bitterns. It is in the monotypic genus Zebrilus. It is found in Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname, and Venezuela. Its natural habitat is subtropical or tropical swamps.
The zigzag heron is a species of the entire Amazon Basin, east of the Andes cordillera, and the five bordering countries on the basin's western periphery, Colombia, Venezuela, Ecuador, Peru, and Bolivia. The range does not extend beyond the Orinoco River basin of Venezuela in the northwest, and in the east-northeast encompasses the Guianas; in the southeast Amazon Basin the range does not extend east of the Tapajós River drainage.
They are reclusive birds, staying hidden in thick cover even while foraging.
The adult plumage is gray with fine zigzag barring, with a pale underside, standing about 32 centimetres (12+1⁄2 inches) in height. Juveniles have a dark back with a brown head and underside. Due to its appearance it was often assigned to the tiger herons (Tigrisoma and allies). But in fact, it is a true bittern, having like these only 10 rectrices (other Ardeidae have 12) and being unequivocally placed in the bittern lineage by DNA sequence data too. Short legs and necks and cryptic plumage may thus be plesiomorphic among Ardeidae in general.
![Zebrilus pumilus = syn. Zebrilus undulatus[1]](https://s3.animalia.bio/animals/photos/medium/original/zebriluspumilus2smit.webp)