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Tagula Butcherbird Cracticus louisiadensis



Justification

Justification of Red List Category
This species has a very small range and a moderately small population, and is likely to be undergoing a continuing decline owing to forest loss and degradation due to logging and subsistence agriculture. However, it probably has more than ten locations, the population size does not meet the threshold for Vulnerable under the population size criterion and the largest subpopulation is unlikely to comprise 100% of the total population. For these reasons, the species is listed as Near Threatened.

Population justification
The species is relatively common in suitable habitats across all four islands (Goulding et al. 2019a). Pre-dawn singing males surveyed during the breeding season in 2012-16 occurred at densities of about 0.53 mature individuals/ha on Sabara Island (Goulding et al. 2019a). The species is more patchily distributed on Panawina (0.15/ha), Junet (0.23/ha) and Tagula (0.14-0.30/ha) where it appears to be at lower densities in suitable habitat and absent from some areas of suitable habitat. Conservative extrapolation using forest cover greater than 80% (79,200 ha; Hansen et al. 2013), combined with the observed densities, suggests that the global population of mature individuals is 11,500 - 23,200, although it was noted that this may be a slight overestimate (Goulding et al. 2019a).

The island with the largest population is Tagula, which was estimated to have a population of 10,000–21,500 mature individuals (Goulding et al2019a). The species has been observed crossing water barriers of at least 500m, so it is suspected to have a high dispersal ability (Goulding et al2019a). However, vocal differences between individuals from Sabara and other islands suggest distinct subpopulations.

Trend justification
Over three generations from 2004-2019, approximately 2.8% of tree cover with 75% canopy cover was lost from within the species's range (Global Forest Watch 2020). Although this loss was small, the species prefers intact forest and is therefore inferred to be undergoing a slow continuing decline. Based on this information, the species is suspected to have undergone a population reduction of 1-5% over the past three generations (15 years). In 2019, there were plans for a large logging operation on Tagula, which could affect up to 10% of the species's range. The population is therefore suspected to undergo a reduction of 1-15% over the next three generations.

Distribution and population

Cracticus louisiadensis is endemic to Tagula (= Sudest) Island (c.800 km2), Junet (=Panatinani) Island (c. 77 km2), Panawina Island (c.  29.5 km2) and Sabara Island (c. 4 km2) in the Louisiade Archipelago of Papua New Guinea (Coates 1990, Goulding et al. 2019). It is absent from the intervening islands of Nimoa, Grass, Piron and Hemenahei (Goulding et al. 2019a).

Ecology

This species occurs in intact forest interior and adjoining forest edge, particularly tall trees for pre-dawn singing during the breeding season. It has been recorded up to 476 m above sea level (Goulding et al.2019a). It is absent from heavily fragmented landscapes lacking contiguous forest cover, and absent near some large human populations and areas with a history of past disturbance, e.g. old coconut plantations on NW of Tagula Island (Goulding et al2019).  Forages in and near mangroves and secondary habitat when these habitats are adjoining contiguous forest. Generally avoids sago stands, isolated and small forest patches or regrowth areas lacking a canopy (Goulding et al. 2019a). Occurs at relatively high densities on Sabara, despite this island having a large and growing human population, but it is an uplifted coralline island unsuitable for subsistence farming. It has been observed most frequently in the canopy layer, followed by the emergent layer and understorey layers (Goulding et al. 2019a). It feeds on arthropods and fruit, including Ficus species, and occasionally on small vertebrates such as small lizards (Goulding et al. 2019a). It nests in the forks of emergent trees or trees slightly isolated from forest margins, such as on the edge of a river (Goulding et al. 2019a).

Threats

Forests on Junet and Panawina are under increasing pressure from subsistence agriculture from growing human populations on Grass and Sabara Islands. Commercial gold prospecting has been occurring in forests of Tagula Island in recent years. Logging has degraded some of the lowland forest on Tagula (Beehler 1993). In 2019, there were plans to commercially log forest on Tagula Island between Reuwo on the south coast and Rambuso Creek on the north coast. Associated roads have also been discussed, that would dissect the island between these two points and along the north coast to Tagula Station (W. Goulding in litt. 2020). The species avoids highly disturbed habitat and prefers forest with a relatively intact canopy (Goulding et al. 2019a). However, forest loss on Tagula has been relatively slow from the 1970s-2010s (Goulding et al. 2019b). Forest loss between 2000 and 2014, caused largely by subsistence gardening, was 1.7% on Tagula, 4.1% on Junet Island, 2.2% on Panawina Island and 0.3% on Sabara Island (Hansen et al. 2013).

Changing climate and more extreme weather events such as cyclones may pose a threat to forest integrity and resources for this species (Goulding et al. 2016a). Around Araetha village on the north coast of Tagula Island, the number of breeding pairs dropped from five to three after Cyclone Ita in 2014 (W. Goulding in litt. 2016). Individuals disappeared that were known by local people to have called from particular locations for numerous years. However, this could have resulted from emigration from the area due to ongoing habitat degradation, rather than from the cyclone (W. Goulding in litt. 2020).

Although the species is of cultural importance, there have been several records of individuals being hunted (Goulding et al. 2019a), and species is absent from areas of suitable habitat in which people had hunted with rifles. There has also been a report of the species appearing in trade in Indonesia (Indraswari et al. 2020, S. Brusland in litt. 2020), but this is unverified and any impact of trade on the species is likely to be negligible.

The genus is known to be vulnerable to disease and parasites (Peirce et al. 2005, Bennett and Gillett 2014, Goulding et al. 2016b). Avian Pox has been observed on Rossel Island, and may pose a risk to this species if it spreads (W. Goulding in litt. 2016). Although several invasive predatory species occur within the range of the Tagula Butcherbird, there is no evidence that it is predated by them.

Conservation actions

Conservation Actions Underway
There is a colour -ringed population on Sabara and studies of the species have taken place on Tagula, Junet and Panawina (W. Goulding in litt. 2016, Goulding et al. 2019a).

Conservation Actions Proposed
Continue surveying suitable habitat on Tagula. Improve understanding of its ecological requirements, tolerance of habitat degradation and threats. Carry out further surveys to confirm the population estimate, monitor population trends and improve knowledge of its demography. Monitor habitat trends. Protect remaining forest within its range. 

Acknowledgements

Text account compilers
Wheatley, H.

Contributors
Brusland, S., Burrows, I., Davis, R., Derhé, M., Dutson, G., Goulding, W. & Symes, A.


Recommended citation
BirdLife International (2021) Species factsheet: Cracticus louisiadensis. Downloaded from http://www.birdlife.org on 04/12/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 04/12/2021.