Within its native range, where it was once widespread and abundant, populations of the Java sparrow have suffered disastrous declines. This has been primarily attributed to exploitation for the domestic and international cage-bird trade, which has been occurring for possibly hundreds of years (4). Ironically, even in other areas of Southeast Asia where the Java sparrow was introduced as a result of cage bird escapes, numbers are now decreasing due to further trapping (7). Unfortunately, the gregarious, flocking nature of the Java sparrow makes it an easy target for bird catchers (4).
In addition to trapping, a number of other threats may hold some responsibility for this species’ decline. The excessive use of pesticides in rice fields in the 1960s may play a greater role in the population declines than is currently known. As the Java sparrow is frequently associated with agricultural land, it is therefore very susceptible to changes in agricultural practices. It is sometimes considered a rice crop-pest and sparrows on rice fields have been heavily persecuted, with adult birds being shot and nests being destroyed. Finally, possible competition with the tree sparrow (Passer montanus), a recent arrival within the range of the Java sparrow, and habitat loss, caused by the invasion of alang-alang grass (Imperata cylindrical), may be contributing to the decline of the Java sparrow (4).