Breeding biology of Java']Javan Hawk-eagle Spizaetus bartelsi in West Java']Java, Indonesia

The Javan Hawk-eagle Spizaetus bartelsi is one of the rarest and least known birds of prey, regarded as globally endangered and confined to the last remnants of forests left on the densely populated island of Java, Indonesia. Its biology is little-known and only a few cases of breeding have been reported. Systematic observations in 1992 and 1994 of two breeding pairs in the rainforest of the Gede-Pangrango National Park, West Java, are described in this paper. In total over 100 h of observation were made and covered different stages of the breeding cycle. Clutches consisted of one egg, incubated for 47 +/- 1 days predominantly by the female, to whom the male brought prey. After the egg hatched the female joined the male in hunting. The male was rarely seen on the nest as copulation and prey transfer took place mainly on nearby trees. After fledging the eaglet stayed near me nest for at least two months. A prolonged post-fledging period followed, the juvenile remaining with its parents for more than one year.