Justification of Red List Category
This species is classified as Vulnerable because it is thought to have a very small population. It has not been seen since its discovery in 1959 and might prove to be more threatened.
There is no evidence for estimating the population size, except for absence records from sites slightly lower than the species's single known historical location. The population size is provisionally placed in the band 250-999 mature individuals.
Buchanan et al. (2008) calculated the rate of habitat loss within the range of this species as c.5% over three generations based on the rate of apparent habitat loss from remote sensing images, but this seems unlikely given its attitudinal range and needs ground-truthing. Less detailed data is available for later years, but the overall rate of forest loss has slowed, with about 2.2% of forest lost and 5.2% degraded across New Britain (mostly in the lowlands) between 2002 and 2014 (Bryan and Shearman 2015).
Megalurulus grosvenori is known from two specimens from the island of New Britain, Papua New Guinea. These were collected in 1959 in the Whiteman Mountains; after the first specimen was collected, only one other pair was found during four days of specific searching (Gilliard 1960). Other historic collectors and recent observers have failed to find this species (K. D. Bishop in litt. 1994, Clay 1994, D. Gibbs in litt. 1994, G. Dutson pers. obs. 1997-1998). However, very few observers have reached the necessary altitudes and thicketbirds are skulking and rarely seen, unless they are calling. The species is likely to be replaced at lower altitudes by Rusty Thicketbird (Ortygocichla rubiginosa), which has been recorded up to 1,400 m (G. Dutson pers. obs. 1997-1998).
The specimens were collected in montane forest on karst limestone at c.1,700 m. The species is believed to forage on the ground, on low stems and up to one metre high in bushes (Dutson 2011).
Forest at the altitudes this species probably inhabits is little threatened by logging or clearance, although small scale habitat degradation has been noted above 1,600 m (Buchanan et al. 2008). The species may possibly be at risk from introduced predatory mammals, particularly rats.
Conservation Actions Underway
None is known.
Text account compilers
Dutson, G., Hermes, C., Derhé, M., Mahood, S.
Beehler, B.M., Bishop, K.D., Gibbs, D. & Wilkinson, R.
BirdLife International (2020) Species factsheet: Megalurulus grosvenori. Downloaded from http://www.birdlife.org on 25/02/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 25/02/2020.