We recorded 62 bird species on Clarion Island, Mexico (Revillagigedo Archipelago, Pacific Ocean) during 1998–2006, eight of which breed there, 52 are considered non-breeders, and breeding is likely but unconfirmed for the Red-billed Tropicbird (Phaethon aethereus), Nazca Booby (Sula granti), and an unidentified shearwater. Thirty species are new for the island. A census of the Clarion Burrowing Owl (Athene cunicularia rostrata) in 2002/03 suggested a maximum total population of ∼850 pairs. At least 46 pairs of Laysan Albatrosses (Phoebastria immutabilis) bred in 2002/03, but the species experienced total breeding failure during our study. This result was unexpected because feral pigs (Sus scrofa) were successfully eradicated from Clarion by 2002; endemic Clarion Ravens (Corvus corax clarionensis), an endemic snake (Clarion Racer, Masticophis anthonyi), and an unidentified ant were associated with egg and hatchling failures. A small colony of an unidentified shearwater could be a recolonization by the endemic and Critically Endangered Townsend's Shearwater (Puffinus auricularis) or Wedge-tailed Shearwater (P. pacificus), which has not been recorded for Clarion Island.