Puu Oo Trail is a historic cattle drive route located at the 6,000 foot (1800 meters) level of Saddle Road on Mauna Loa's northeastern flank. This is the windward side of the island and is often cloaked in misty clouds. It is enchanting to be serenaded by the forest birds as you cross three to four miles (5-6 km) of lava trail. At the Humuula hunter check-in station just off Saddle Road, you'll go into the Kaohe Game Management Area and four-wheel up to nearly 7,000 feet (2,100 meters) on the western side of Mauna Kea.
Some of the avifauna you may spot along the way are iiwi, apapane, amakihi, omao, elepaio, and the elusive akiapolaau, with its unique multipurpose beak. In the dryforest, the track leads to a locked gate that is the entrance to the Mauna Kea Forest Preserve. Here, you'll have the opportunity to disembark from the van and take in the spectacular views. Then get down to some serious bird watching on foot in the mamane-naio forest.
You'll particularly focus on sighting the critically threatened palila, which feeds almost entirely on the green pods of the mamane tree. There are two other endemics of note to be found here: the Hawaii amakihi, and the local species of the Hawaii elepaio (noted for the white feathering on its head).