The nun (Arundinicola leucocephala) is a passerine bird in the Tyrannidae family. It is the only species of the genus Arundinicola. Also known as a laundress-to-head-white, valet-of-our-lady, Maria-old woman, viuvinha, viuvinha-the-swamp, head-to-washer and head-to-grandfather.
The male is almost all black, with only the head and the white throat. The female has the brown-gray upper parts, the whitish lower and only the white forehead. Immature are gray.
The tail, small, opposed to the relatively large head (emphasized by keeping the feathers a little ruffled). It features a 14-gram weight and length 14 cm.
It feeds on insects capture in flight.
Normally lives to couples. The nest, ball-shaped, resembles the Masked Water-(nengeta F.). The interior of the nest is lined with feathers of other birds and is always put in some background on the water. The position appears 2-4 eggs creamy white color with small red spots. The cubs are born covered with a long pale yellow plumage, imitating a toxic caterpillar.
Common in swamps, marshes, riverbanks and lakes. Remains most of the time resting on the top of the aquatic vegetation or in trunks and lower branches on the water. Runs short and quick flights to catch insects. This species lives exclusively by water, differing from F. nengeta which can also occur and nest away from water.