It was first described by Blasius Merrem in 1786. It had reached a size of 32 cm or about 13 inches in length. The wing length was 110 to 115 mm. The tail reached a length up to 19 cm. The colour of its plumage was glossy black with a brown shading at the belly. It was further characterized by yellowish tufts at the axillaries. It had some yellowish plmes on its rump, but lacked yellow thigh feathers like the Bishops O'o', and also lacked the whitish edgings on its tail feathers like the Oahu O'o'. However it had the largest yellow plumes on its wings out of all the species of O'o'.
At the time of discovery by Europeans, it was still relatively common on the Big Island, but that was soon to change. The Hawaii ʻŌʻō was extensively hunted by Native Hawaiians. Its striking plumage was used for the royal robes and capes. The Europeans too saw the striking beauty of this bird and hunted many of them for specimens in personal collections. Some were even caught and were put in cages to be sold as song birds only to live for a few weeks or days before diseases from mosquitos hade befallen upon them. The decline of this bird was hastened by both natives and Europeans by the introduction of the musket which allowed hunter and collectors to shoot birds down from far away places and from great heights and numbers. In in the year of 1892, the birds were shot in great number, almost 1,500 of them were killed and this major shooting had been occurring for almost every year from the time it was first discovered by Europeans back in 1786, meanig the bird has been able to survive for nearly 130 years with major decreases in the population. After this the birds became too rare to be shot in any great quantities but was continued to be found for nearly 30 more years. It was last heard in 1934 on the slopes of Mauna Loa.