Radio-tracking and territory mapping in plateau primary forests mainly
during the dry season revealed that Christmas Island Hawk-Owls Ninox
natalis occupied essentially exclusive territories with an average are
a of c. 18 ha. Estimates of home range size from radio-tracking data c
ollected over a period of 10 to 67 d were smaller (males 13 ha, 10.6 h
a, 10.1 ha, 9.5 ha and 5.5 ha; females 6 ha and 7 ha) but in general s
upported the conclusions from territory mapping data. Christmas Island
Hawk-Owls were widespread on the island in both primary and disturbed
habitats. Call-playback censusing of 22 sites repeated five times det
ected no significant difference in the relative abundance of owls betw
een primary forests on the plateau and the surrounding terraces and sc
ree slopes; significantly fewer owls were detected in regrowth forest.
These results provide an estimate of 562 +/- 105 occupied owl territo
ries on the island. From this we estimate that there may be fewer than
1000 mature Christmas Island Hawk-Owls remaining and recommend that t
his taxon remain listed as Vulnerable.