Justification of Red List Category
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be fluctuating, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
The overall population trend is fluctuating, although some populations are stable and others have unknown trends (Wetlands International 2006).
Nycticorax caledonicus occurs in the Philippines, Indonesia, Australia, Papua New Guinea, the Solomon Islands, Palau, New Caledonia (to France) and the Caroline Islands, Federated States of Micronesia. The subspecies crassirostris, which was endemic to Japan's Bonin Islands, has been extinct since the late 1800s (del Hoyo et al. 1992).
Text account compilers
Butchart, S., Ekstrom, J., Khwaja, N.
BirdLife International (2020) Species factsheet: Nycticorax caledonicus. Downloaded from http://www.birdlife.org on 26/01/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 26/01/2020.