Abstract
Crab plovers Dromas ardeola are shorebirds endemic to the coasts of the Indo-West Pacific biogeographical area. Very little is known about the migration of this enigmatic bird. Here, we studied the migratory itineraries of six crab plovers tracked between their wintering grounds in Barr Al Hikman, Oman, and their breeding grounds on islands in the north-west of the Arabian/Persian Gulf in Iran and Kuwait. During spring migration, all tagged birds followed a similar route. On the first leg, birds flew north over desert and mountain areas. After reaching the Arabian/Persian Gulf, they followed the northern coastline, where most birds had several stops. Birds initiated spring migratory flight between February 28 and May 7, and it took 3-24 days to travel from the non-breeding to the breeding areas. The birds spent between 96 and 174 days at the breeding colonies. Autumn migratory flights were mostly along the eastern coast of the Arabian/Persian Gulf. Four birds followed a coastal route back to Barr Al Hikman, similar to spring migration. Two birds followed a southerly route and short-cut the last stretch of 500 km by crossing the Empty Quarter (Rub Al Khali) desert region. Autumn migratory flights occurred between July 19 and October 24, lasting 3-91 days. Most migratory flights occurred predominantly between 6 p.m. and 6 a.m. and were almost always less than 25 m altitude above the Earth's surface. The maximum height of 1748 m above sea level was measured above the Oman Mountains. Crab plovers were able to cross potential barriers (i.e., the two desert areas and a mountain range) within a single night. We discuss our results with respect to the migratory connectivity known for this species.