ATTEMPTED PREDATION ON A LARGE-TAILED NIGHTJAR ( CAPRIMULGUS MACRURUS) BY AN EASTERN MARSH-HARRIER ( CIRCUS SPILONOTUS) IN COASTAL VIETNAM

摘要

This note describes a predation attempt on a Large-tailed Nightjar (Caprimulgus macrurus) by an Eastern Marsh-Harrier (Circus spilonotus) at Nha Trang Airport (109°11'0"E, 12°14'0"N), Vietnam. Observations took place from 0650-0700 H on 28 February2004. An adult male Eastern Marsh-Harrier was observed slow quartering at varying heights (between 2—10 m above the ground) over the airport terrain of concrete interspersed with overgrown grass and scrub. I observed no predation attempts within the first 5 min of observations. The marsh-harrier then glided very low (1-2 m above ground), braked abruptly in flight, almost turning over, and dropped toward the ground. The apparent attack was unsuccessful, and the presumed intended prey, a Large-tailed Nightjar, flew from the exact location where the marsh-harrier landed and rose rapidly to a height of ca. 10-15 m. The marsh-harrier remained grounded for 1-2 sec and did not actively pursue the nightjar, which flew eastward at a constant height (10-15 m) toward the coast some 80—100 m away and out of sight. The marsh-harrier continued its systematic quartering ca. 3 sec after its failed strike, but no further predation attempts were made in the following 5 min.