摘要：Summary The avian genus Progne (martins) is well known for its tendency to roost in aggregations of thousands of individuals. A concentration of approximately 100.000 Progne modesta (southern martins) with 5.000 P. subis (purple martins) in the Peruvian Amazon city of Iquitos in September 1978 is described, with a history of the species occurance in the area. Up to 250.000 individuals of the two species roosted in the Plaza de Armas of Iquitos from April to mid-August 1978. when trees used as roosting sites were cut in an attempt to drive the birds away. By virtue of a rescue effort to replace the lost perches, 100.000 birds were still found in the plaza in mid-September, the remainder having died or left. In September the birds distinctly preferred the southern quadrate of the plaza, and the significance of this distribution in relation to migratory restlessness is discussed. All birds left the plaza by the first week in October, presumably to fly south to breeding grounds in Argentina, Bolivia and Paraguay.
其他摘要：Summary The avian genus Progne (martins) is well known for its tendency to roost in aggregations of thousands of individuals. A concentration of approximately 100.000 Progne modesta (southern martins) with 5.000 P. subis (purple martins) in the Peruvian Amazon city of Iquitos in September 1978 is described, with a history of the species occurance in the area. Up to 250.000 individuals of the two species roosted in the Plaza de Armas of Iquitos from April to mid-August 1978. when trees used as roosting sites were cut in an attempt to drive the birds away. By virtue of a rescue effort to replace the lost perches, 100.000 birds were still found in the plaza in mid-September, the remainder having died or left. In September the birds distinctly preferred the southern quadrate of the plaza, and the significance of this distribution in relation to migratory restlessness is discussed. All birds left the plaza by the first week in October, presumably to fly south to breeding grounds in Argentina, Bolivia and Paraguay.
