Heraldsturmvogel Pterodroma heraldica

Medium-sized, lightly built petrel of offshore tropical waters across the Pacific; not seen from mainland. Plumage is highly variable (from white-bodied and dark-headed to wholly dark) and often very similar to larger and broader-winged Kermadec Petrel, which has a shorter and broader tail than Herald. Herald has white flashes on underside of wingtips, but lacks white shafts on upperside, which are diagnostic of Kermadec. Both species visit colonies in daytime, when pairs chase around high overhead.