The plumage is dark, varying from blackish on the head and breast to olive-green on the wings and body.

A single whitish brown speckled egg is laid in a simple sticky cup nest.

After leaving the nest the juvenile remains in the core breeding territory where it is fed by the female for 2–2.5 additional months.

It is a noisy bird with beautiful loud whistling and mewing calls given most often prior to dawn and around dusk.

In December 2014, the United States Fish and Wildlife Service announced the Ma‘oma‘o as a candidate for ESA protection, describing the species as "a large, dusky olive-green honeyeater native to Upolu and Savaii, Independent Samoa (Samoa), and Tutuila Island, American Samoa, but now only found in small populations on the islands of Savaii and Upolu.