Distribution and patterns of migration of a tropical seabird community in the Eastern Indian Ocean

We present the first detailed data on the distribution and migration patterns of four pelagic seabird species in the Eastern Indian Ocean—the Lesser Noddy (Anous tenuirostris melanops), Brown Noddy (Anous stolidus), Wedge-tailed Shearwater (Ardenna pacifica) and Bridled Tern (Onychoprion anaethetus) breeding at the Houtman Abrolhos and the Wedge-tailed Shearwater breeding at Varanus Island, Western Australia—tracked using geolocators during their respective non-breeding periods. Lesser Noddies remained largely in the general vicinity or slightly to the south of the colony in their non-breeding season (February–September). Brown Noddies spent their non-breeding period (March–August) in the Northwest Shelf area of Western Australia, around 950 km north of the colony. In contrast, Bridled Terns and most Wedge-tailed Shearwaters undertook extensive non-breeding migrations. Wedge-tailed Shearwaters occupied waters adjacent or to the north of their nesting sites or migrated 4200 km northwest into the equatorial central Indian Ocean near the Ninety East Ridge during the non-breeding season (late April to mid-November). These same areas were used during the sabbatical summer by Wedge-tailed Shearwaters that had deferred breeding. Bridled Terns spent their non-breeding period (April–September) in the Celebes Sea, 3800 km north of the Houtman Abrolhos. The results are discussed in the context of potential marine threats to the different species during the non-breeding period.