The sexes are similar but the juvenile plumages are distinctive.

The two were previously classified as a single species but are now often separated based on differences in calls and juvenile plumage.

Some birds breeding for the first time in tropical areas are only a few months old and still have juvenile plumage.

The chicks moult into their juvenile plumage and go out to sea after 50 to 60 days.

The sexes are similar, and the juvenile plumage is undescribed.

It seems that males keep their juvenile plumage for up to three months, and take a similar period to come into full colour.

During this period, the young become covered in juvenile plumage while remaining in the hollow.

It also has a distinct juvenile plumage, more rufous above and with heavy pattern, especially below.

The sexes are similar, but juvenile plumage is grey brown above apart from the white rump.

The juvenile plumage is much like the female's but with heavier streaking.