The Serra do Mar Tyrannulet (Phylloscartes difficilis) is a small species of bird

Bird

Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

 in the Tyrannidae family. It is endemic to humid montane forest in the Serra do Mar

Serra do Mar

Serra do Mar is a 1,500 km long system of mountain ranges and escarpments in Southeastern Brazil, which runs in parallel to the Atlantic Ocean coast from the state of Espírito Santo to southern Santa Catarina, although some include Serra Geral in the Serra do Mar, in which case this range...

 in south-eastern Brazil

Brazil

Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

. More likely confused with the short-tailed and pale-eyed Hangnest Tody-tyrant

Hangnest Tody-tyrant

The Hangnest Tody-Tyrant is a species of bird in the Tyrannidae family.It is endemic to Brazil.Its natural habitats are subtropical or tropical moist lowland forests and heavily degraded former forest.-References:...

 than other members of the genus Phylloscartes

Phylloscartes

Phylloscartes is a genus of small birds in the Tyrannidae family. They are found in wooded habitats of Central and South America. The Mottled-cheeked Tyrannulet is among the commonest birds in its range, but several other species are rare and threatened. Their plumage is predominantly green,...

, its bright olive-green upperparts contrast strongly with the grey underparts. It is generally uncommon and threatened by habitat loss.