Tropical shearwater

Lore & Background

The species ranges across tropical waters from East Africa to southern India and from southeast of Japan to French Polynesia. The largest single-island population is on Aride Island in Seychelles, with an estimated 26,118 pairs. Smaller numbers of the nominate subspecies breed on nearby rat-free islands, and other subspecies have varying population estimates across the Pacific.

Reader's Guide

The tropical shearwater is significant as a distinct species within the Procellariidae family, having been separated from Audubon's shearwater. Its population status is notable for being stable but not definitively quantified, with key breeding colonies on islands in the Indian and Pacific Oceans. The species' reliance on rat-free islands for breeding highlights conservation concerns for seabirds vulnerable to introduced predators. The subspecies P. b. bailloni numbers 3,000–5,000 pairs on Réunion and fewer than 100 individuals on Europa, while P. b. dichrous is estimated at 1,000–10,000 pairs on the Line Islands and 10,000–100,000 pairs on the Phoenix Islands. The presence of many unquantified breeding colonies in the Pacific suggests the total population may be larger than current estimates. The species serves as an example of taxonomic revision in seabirds and the importance of island ecosystems for seabird conservation.

Did You Know?

• The tropical shearwater was formerly considered conspecific with Audubon's shearwater.
• Aride Island in Seychelles has the world's largest single-island population, with an estimated 26,118 pairs.
• The subspecies P. b. bailloni numbers fewer than 100 individuals on Europa.
• The total population of the tropical shearwater has not been definitively quantified.