Archived 2011-2012 topics: Philippine Fairy-bluebird (Irena cyanogastra): eligible for uplisting?

Initial deadline for comments: 31 January 2012.

BirdLife species factsheet for Philippine Fairy-bluebird

Philippine Fairy-bluebird Irena cyanogastra is endemic to the Philippines, where it is found mainly in closed-canopy broadleaved evergreen forest, but also forest edge and perhaps secondary growth, to 1,500 m on Luzon, Cataduanes, Polillo, Bohol, Leyte, Samar, Dinagat, Mindanao and Basilan (Kennedy et al. 2000, del Hoyo et al. 2005). It is listed as being of Least Concern on the basis that it was not thought to approach the thresholds for Vulnerable under any of the IUCN criteria.

This species has a very large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (B and D2: Extent of Occurrence [EOO] of less than 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). Despite the fact that the population trend appears to be decreasing, the decline was not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (A: at least a 30% decline over ten years or three generations). The population size has not been quantified, but it is not believed to approach the thresholds for Vulnerable under the population size criteria (C and D1: fewer than 10,000 mature individuals with a continuing decline estimated to be at least a 10% in ten years or three generations, or with a specified population structure).

Although this species is common, its population is suspected to be in decline owing to on-going habitat destruction and fragmentation (del Hoyo et al. 2005). The wholesale clearance of forest habitats is taking place as a result of logging, agricultural conversion and mining activities.

In 1988, an estimated 24% of Luzon remained forested. Forest cover in the Sierra Madre has declined by at least 83% since the 1930s and most remaining areas are under logging concession. Major road building plans pose a further threat. Illegal logging is frequent in some protected areas.

Just 29% of Mindanao remained forested in 1988, and this is now thought to be a considerable overestimate. Most remaining lowland forest is now leased to logging concessions or mining applications, and there are current explorations in high elevation areas.

On Dinagat, forest is being rapidly cleared for surface-mining (D. Allen in litt. 2011). Logging operations on Basilan in the 1960s, followed by clearance for agriculture and increased hunting, have undoubtedly impacted the species. Forest in some areas, especially in the lowlands, is being cleared under concession and re-planted with exotic trees for paper production.

Estimates from 1989 were that as little as 433 km2 of old-growth dipterocarp forest remained on Samar and Leyte. Just 4% forest cover (c.151 km2) is thought to remain on Bohol. Much remaining lowland forest is leased to logging concessions, and mining applications pose an additional threat. Local pressures include limited illegal tree-cutting, agricultural expansion and soil erosion. Mining for chromite and nickel represents the most significant threat to many remaining forest areas (J. Ibanez in litt. 2007).

Comments and further information are requested in order to assist with this species’s Red List assessment. In particular, up-to-date estimates of remaining forest cover and rates of deforestation are sought. If evidence suggests that the population has or is projected to decline at a rate approaching 30% (typically 20-29%) over three generations (13 years, based on a generation length of c.4.2 years; BirdLife International unpubl. data) then the species may be eligible for uplisting to Near Threatened under criterion A. The species would be likely to qualify as Vulnerable if there were suspected to be a decline of at least 30% over three generations, and uplisting to Endangered might be justified if the rate of decline were suspected to be at least 50% over the same time frame.

References:

del Hoyo, J., Elliott, A. and Christie, D. (2005) Handbook of the Birds of the World, vol. 10: Cuckoo-shrikes to Thrushes. Barcelona, Spain: Lynx Edicions.

Kennedy, R. S., Gonzales, P. C., Dickinson, E. C., Miranda, H. C., Jr. and Fisher, T. H. (2000) A Guide to the Birds of the Philippines. Oxford, UK: Oxford University Press.

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3 Responses to Archived 2011-2012 topics: Philippine Fairy-bluebird (Irena cyanogastra): eligible for uplisting?

  1. Ding Li Yong says:

    Philippine fairy bluebird appears to be primarily dependant on lowland forests though the species can range up to submontane elevations. Local densities of the species however appears to be relatively low, compared to the Asian fairy bluebird. In Mount Makiling, Los Banos, the species appeared very uncommon in secondary/primary hill forest and i found only one individual after 20 hours in the field. In Subic Bay forest, the species appeared to be more abundant, and two to three individuals were detected over two hours, suggesting that forests at low elevation formed the core habitat. In PICOP (Surigao del Sur, Mindanao) and Rajah Sikatuna National Park (Bohol), the species appear to occur at generally low densities, unless at fruiting trees. On the other hand, Philippine fairy bluebird could utilise forests on limestone which tend to be of lower stature and may have even lower densities of fruiting trees. In northern Luzon, (Mt Los Dos Cuernos) in the Sierra Madre range, the species occur even in submontane forests, but again at low densities, with encounter rates of two to three birds a day (unless at fruiting figs). Given a combination of restricted range, and that more than 50% of its habitat has been lost across the Philippin archipelago, and that deforestation rates in the lowlands of Mindanao remain high, it may be appropriate to upgrade the species to at least Near Threatened.

  2. I would agree with Ding Li’s assessment that the Philippine Fairy Bluebird occurs at low densities even where found and is certainly affected by deforestation as evident at PICOP where the species has declined tremendously over the last 10 years and is now difficult to find. I wouldn’t necessarily agree that the species is commonest in lowland forest, the highest densities I have found are at Mount Dos Cuernos at 700-950masl where in April I have seen as many as 10 individuals along 1.5 km of ridge trail. Given the species clear dependence on primary or tall secondary forest and the rate of forest destruction this species must qualify at least as near threatened and perhaps endangered.

  3. Desmond Allen says:

    I agree with Rob. It is always worth remembering that in the Philippines ‘species’ can vary significantly between island groupings. The ecology of the Luzon, Black-mantled and Ella’s Fairy Bluebirds may be different and each is certainly worthy of conservation. Since birds of this size probably survive for many years without breeding once their habitat has been too badly damaged it is hard to assess their habitat requirements. They seem to prefer moister Pacific forests, eg tall forest of the Sierra Madre, Mt Isarog, and not the Cordillera. If you contact the various US museums that have been doing collecting, the BirdLife partner, etc you should be able to build up a picture of the distribution over much of its range.

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