Population Changes of the Torresian Imperial-Pigeon Ducula spilorrhoa Over Twenty-one Years on North Brook Island, North Queensland

Abstract

Torresian Imperial-Pigeons, a breeding summer migrant to northern Australia, were counted during their evening return flight to North Brook Island, 29 km off Cardwell, from 1965166 to 1985186. In the first four years numbers declined from 4692 to a low of 145 1 in the 196819 season, followed by a recovery over eight years to a December maximum of 9808. Thereafter, counts have fluctuated between about 10 000- 13 000 Imperial-Pigeons returning to the island in the evening flight, except for a sudden increase to 21 815 in January 1986. The population decline is attributed to shooting of the Imperial-Pigeons at the nesting colony, and the population recovery to subsequent protection.