Prior to 1994, a chemical process to meet hydrogen needs was used. This process produced a toxic residue that was a danger to the local birdlife. Because of this danger, a safer "electrolytic converter" is now used to break down water into hydrogen and oxygen. The most common inhabitants are wedge-tailed shearwaters, sooty terns and common and black noddies. Their numbers are usually quite high and bird cries continue day and night on the island. Several species of booby migrate through the Island including masked, brown and red-footed boobies, and also the lesser frigatebird. Crested terns are also seen to migrate, although not as often. Other birds mentioned by John King Davis are the buff-banded rail as a resident, wood sandpiper, and sacred kingfisher and red-tailed tropicbird as occasional visitors.