Forest Bittern Zonerodius heliosylus


Justification of Red List Category
This species qualifies as Near Threatened because it has a moderately small population which is thought to be undergoing a slow to moderate decline owing to habitat degradation. Further evidence to suggest that the rate of decline may be slower than previously assessed may mean that this species warrants downlisting in the future.

Population justification
Fewer than 10,000 individuals are estimated to survive (unpublished information supplied by Wetlands International Specialist Groups), so it is placed in the band 2,500-9,999 individuals here. This equates to 1,667-6,666 mature individuals, rounded here to 1,500-7,000 mature individuals.

Trend justification
The population is suspected to be slowly declining owing to ongoing habitat destruction. Across the mainland coastal provinces of Papua New Guinea, 1.3% forest was lost plus 2.5% was logged between 2002 and 2014 (Bryan and Shearman 2015). Although the species' tolerance of logged forest is not known, all records appear to have been from old-growth forest, and its rate of population decline is assessed as 1-9% in three generations (22 years).

Distribution and population

Zonerodius heliosylus occurs throughout New Guinea (Papua, formerly Irian Jaya, Indonesia and Papua New Guinea) and on the adjacent islands of Salawati and Aru, Indonesia. There are few recent records but it appears to be widespread from the lowlands to 1,650 m (Sam and Koane 2014, Beehler and Pratt 2016).


It frequents streams, pools and swamps in forest to 1,650 m (Sam and Koane 2014) and forages on the edges of forest creeks and pools on fish, reptiles, crustaceans and insects (Pratt and Beehler 2015, Sam and Koane 2014). Bulky nests are built in forest midstory (Pratt and Beehler 2015).


Although it is not hunted (B. M. Beehler in litt. 1994) and there are still huge areas of suitable habitat left, it may be threatened by the extensive logging of lowland forest (I. Burrows in litt. 1994, R. Burrows in litt. 1994), especially as it occurs along watercourses (A. Mack in litt. 1999).

Conservation actions

Conservation Actions Underway
None is known.

Conservation Actions Proposed
Survey to better understand the abundance and distribution of the species. Protect large areas of lowland rainforest. Ensure protection of forests along watercourses.


Text account compilers
O'Brien, A., Derhé, M., Wheatley, H., Benstead, P., Mahood, S., Dutson, G., Pilgrim, J.

Dutson, G., Bishop, P., Mack, A., Burrows, I., Beehler, B., Gibbs, D., Burrows, R.

Recommended citation
BirdLife International (2019) Species factsheet: Zonerodius heliosylus. Downloaded from http://www.birdlife.org on 23/09/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 23/09/2019.