• Summary
• Text account
• Data table and detailed info
• Distribution map
• Reference and further resources

Justification of Red List category
This species is assessed as Vulnerable because it is inferred to be rapidly declining as a result of habitat loss and degradation, owing primarily to a local agricultural trend away from plantation crops and towards open farmland. Surveys are needed to confirm the species' population status as it has been suggest that the species is much rarer than currently inferred, and therefore a higher threat category may be appropriate in the future.

Population justification
Even with intensive surveying across the island, the species is still relatively 'uncommon' (Catry et al. 2000). More recent visitors to Pemba have struggled to find this species at all, which now appears to be rare (A. Sander in litt. 2004, M. Virani in litt. 2005, J. Wolstencroft in litt. 2005, 2007, N. Burgess in litt. 2012). The population was inferred to be 2,000-3,200 individuals (5-8 individuals/km² x 400 km² [45% of EOO]), based on a density range from the lower and upper quartile of six congeners. This requires validation, and as a result the suspected population size is placed in the band 2,500-9,999 mature individuals. This equates to 3,750-14,999 individuals, rounded here to 3,500-15,000 individuals. However, it has been suggested that the total population may actually number fewer than 500 individuals (J. Wolstencroft in litt. 2007), so further investigation is recommended.

Trend justification
Despite being classed as relatively uncommon in 2000, more recent visitors to Pemba have struggled to find this species at all, which now appears to be rare (A. Sander in litt. 2004, M. Virani in litt. 2005, J. Wolstencroft in litt. 2005, 2007, N. Burgess in litt. 2012), suggesting a decline is ongoing. Tree cover loss within the range is currently estimated at 22% across three generations (13.4 years) (Global Forest Watch 2021, using Hansen et al. [2013] data and methods disclosed therein). As the species is highly forest dependent and does not adapt well to open habitats, population declines are precautionarily suspected to fall between 25-30% over three generations. In particular, loss and degradation of both primary and secondary habitat is occurring (A. Hija in litt. 2005, Virani 2005, M. Virani in litt. 2005, J. Wolstencroft in litt. 2007), with Zanzibar's (Pemba and Unguja) forest declining at 1.2% per year (Siex et al. 2013). This is likely to decrease densities of this species at a slow rate (Catry et al. 2000). There is also a local agricultural trend away from plantation crops and towards open farmland, and if this trend persists, the species could become seriously threatened as it does not seem to be able to adapt well to open farmland habitats (Catry et al. 2000).

This species is endemic to Pemba and adjacent offshore coral islets, some 55 km off the coast of northern Tanzania. Although occurring over most of the island, it is most common in the two small remaining native forests; Ngezi (14 km²) and Msitu Mkuu (3 km²) (Catry et al. 2000).

This species occurs in a number of forested habitats, including secondary growth, clove plantations, and gardens, but is much more common in native, primary forest (Catry et al. 2000). It feeds on a variety of fruit high in the canopy. Breeding has been recorded from October-February, with nests found even near human habitation or in plantations (B. Peters in litt. 2005). The flimsy nest platform is made of twigs, and contains one or two eggs.

Decreasing world clove prices led to the conversion of some old clove plantations (which offered suitable habitat) to open farmland growing rice and cassava (Catry et al. 2000, Virani 2005, M. Virani in litt. 2005, J. Wolstencroft in litt. 2007). Low-statue coral rag woodland, marginal agricultural land and dry scrub are also being cleared for cultivation (J. Wolstencroft in litt. 2007). Wooded knolls and extensively managed plantations, where the species could occur, are also in decline (J. Wolstencroft in litt. 2007). The human population of Pemba continues to rise (400 individuals/km², and increasing by 5% per year [Siex 2011]), and although agriculture remains small-scale, the need for crop-land is intensifying rapidly (J. Wolstencroft in litt. 2007, N. Burgess in litt. 2012). The vast majority of the human population is dependent upon shifting cultivation and forest products, such as building poles, firewood, and charcoal. Due to the high price of electricity, even the urban population is heavily reliant on firewood and charcoal for cooking, and Zanzibar as a whole is losing an estimated 1.2% of its forest each year, leading to increasing fragmentation and rapidly diminishing any potential to maintain and restore connectivity of forest patches (Siex 2011). Some native forest has also been converted to rubber plantation (Virani 2005). Ras Kiuyu forest has been heavily exploited for building materials, lime burning and fuel wood (A. Hija in litt. 2005, N. Burgess in litt. 2012) and Msitu Mkuu Forest Reserve is subject to illegal exploitation (A. Hija in litt. 2005, N. Burgess in litt. 2012). Non-native House Crows (Corvus splendens) may also predate nests for both eggs and chicks (F. Reid in litt. 2005, Roy et al. 2015). Green-pigeons are also particularly popular gamebirds in other regions, and therefore hunting could be a potential additional threat (S. Brusland in litt. 2022).

Conservation Actions Underway
Protected areas on Pemba include Ngezi-Vumawinbi Nature Reserve, Msitu Mkuu Forest Reserve and Ras Kiuyu Proposed Forest Reserve (Siex 2011). There are also 13 community forests which include "high protection" and "low impact use" zones (Siex 2011).

Conservation Actions Proposed
Conduct surveys to assess its population size. Once a baseline estimate of the population size has been obtained, continue to monitor population trends. Monitor rates of habitat loss and degradation. Combine research into habitat loss and population trends with in-depth ecological studies of the species. Control illegal activities within the Forest Reserves (A. Hija in litt. 2005). Improve sustainable tourism facilities at Ngezi Nature Reserve (N. Burgess in litt. 2012). Protect additional areas of forest and off-shore islands (J. Wolstencroft in litt. 2007). Encourage the planting of suitable fruiting trees, especially in tourist areas (J. Wolstencroft in litt. 2007). Promote sensitive tourist development (J. Wolstencroft in litt. 2007). Carry out survey work to determine if there is potential to restore connectivity of forest patches via enrichment planting (Siex 2011).

25 cm. Smallish, arboreal, pigeon. Adults are dull green with grey head, neck and underparts, large purple shoulder patch, and scalloped green-yellow, chestnut, and cream-coloured vent and undertail coverts. Immatures are duller and lack shoulder patch. Similar spp. None in range. Voice Similar to African Green-pigeon Treron calva, but slightly softer. The three- or four-part call consists of a series of fluty whistles or trills, interspersed with grunts and growls. Also a rather quiet cluck.

Text account compilers
Rotton, H.

Contributors
Brusland, S., Burgess, N., Butchart, S., Ekstrom, J., Hija, A., Khwaja, N., Peters, B., Pilgrim, J., Reid, F., Robertson, P., Sander, A., Starkey, M., Symes, A., Taylor, J., Virani, M., Westrip, J.R.S. & Wolstencroft, J.

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Recommended citation
BirdLife International (2024) Species factsheet: Pemba Green-pigeon Treron pembaensis. Downloaded from https://datazone.birdlife.org/species/factsheet/pemba-green-pigeon-treron-pembaensis on 24/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from https://datazone.birdlife.org/species/search on 24/11/2024.