Over the last five years ornithological teams from Operation Wallacea have completed biodiversity and distribution surveys of the avifauna of Buton Island. These surveys have generated species lists, identification notes (particularly where Buton birds differ from their mainland counterparts) and observations on general habitat usage by each of the species (Catterall, 1999, 2000 and in prep., Robinson Dean in prep.). 55 endemic species have been recorded from the island as well as good populations of other non-endemic species that are threatened in many other areas within their range.

Logging, however, is widespread on the island and the human population is increasing rapidly, augmented by transmigration from other more populated islands. It is possible that some of the endemic and threatened bird species may be under threat on Buton Island. The Lambusanga Forest Reserve area in central Buton Island provides a fairly well protected refuge for many of these species. 

Quantitative data are required on the existing population levels of the avifauna in this area. These data combined with observations on life expectancy and breeding and recruitment rates from other studies would give a first indication of whether the protected areas are sufficiently large to provide viable populations. In addition, habitat measurements of where the various species occur, both inside and outside the protected forest areas, are required to determine more accurately their habitat requirements and whether these habitats are fully represented in the protected areas. Precise data on population levels of the various forest bird species will also provide a strong baseline against which annual population fluctuations can be monitored.

The objectives of this year’s study were: 

• To determine the population levels of the local avifauna in the Lambusanga Forest Reserve area to a precision of 20% or less.
• To use Discriminant Function Analysis to assess the habitat associations of the study species.
• To assess whether the population sizes of the various bird species in the Lambusanga Forest area are viable

Radial transects (1.5km long) were cut from the NE and SE corners of the Lambusanga grid at 30° intervals, to survey the surrounding forest area. Point count sites were marked at intervals of 250 paces (apx 250m) along each of these transects. Trained surveyors recorded all birds seen and heard and the distance of each from the point count site. Surveys were conducted in the mornings, between 06:00 and 09:00. Each of the point counts lasted 10 minutes. As the surveyors approached the site they recorded any birds flushed away and their take off point. At each of the sites there was a two-minute ‘calming’ period allowed before recording began. Birds were recorded as sightings, calls or both. If a flock was recorded, the distance to the centre of gravity of the flock was noted. The height of each bird above ground level was also recorded in the following categories: ground (<1m); low (1-5m); medium (5-15m) and high (over 15m). Any flying birds that were not seen to take off were recorded separately. Each point count was conducted once in July and once in August, to allow for any seasonal variation. The data from these two counts were combined to produce a single list for each site. A total of 100 sites were recorded over the duration of the survey (early July to late August 2001).

The habitat within a 30m radius of each point count site was also recorded. The following measurements were taken:

• Forest Structure (e.g. tree height classes, DBH classes, sapling regeneration)
• Light indicators (natural and man-made gap formation)
• Tree architecture was recorded following the method described in Jones et al. (1995). For each mature tree in the study area, the height of the point of first inversion (site of the lowest major branch) was recorded (whether above or below half of the height of the tree). The presence of large scars below the point of first inversion and the direction of growth above the inversion were also noted. In areas which have been clear felled the trees branch much closer to the ground, at a point which is usually well below half the eventual height of the tree. In secondary forest that is maturing, or in light gaps created by tree falls, there may be a secondary reaction to the closing of the canopy. This may result in the tree shedding its lower branches (which will be evidenced by major scars) or in the lower branches growing nearly vertically up towards the canopy. The tree architecture factors were converted to indicator scores to rank the point sites in terms of the levels of disturbance.

A number of rarer species have been identified in the Lambusanga reserve to date. These include Yellow-crested Cockatoo (Cacatua sulphurea), Sulawesi Hawk Cuckoo (Cuculus crassirostris), Ochre-bellied Hawk Owl (Ninox ochracea), Sulawesi Dwarf Kingfisher (Ceyx fallax), Red-backed Thrush (Zoothera erythronota), Pale-bellied White Eye (Zosterops consobrinorum) and Pied Cuckoo Shrike (Coracina bicolor). Incidental records from the surrounding area include Sulawesi Nightjar (Caprimulgus celebensis).

A paper entitled  The effects of forest disturbance on bird communities will be submitted to the Journal of Tropical Ecology by April 2003  by Kelly, D.J. Drayton, M. Gregory, A. Griffith, S. Smith, J & White, D. 

A dissertation report utilising these data was prepared by Neil Reid, Queens University Belfast.  This dissertation was awarded a First.

Bibby, C.J., Burgess, N.D. and Hill, D.A. (1992) Bird Census Techniques. Academic Press, London.

Catterall, M. (1999) A checklist of the birds of Buton Island with notes on their identification features. Operation Wallacea Report. Available on the Operation Wallacea web site.

Catterall, M. (in prep.) The owl and nightjar fauna of the islands of S.E. Sulawesi. To be available on the Operation Wallacea web site before the start of the 2002 season.

Jones, M.J., Linsley, M.D. and Marsden, S.J. (199?) Population sizes, status and habitat associations of the restricted-range bird species of Sumba, Indonesia. Bird Conservation International 5: 21-52.

Laake, J.L., Buckland, S.T., Anderson, D.R. and Burnham, K.P. (1993) Distance User’s Guide Fort Collins, USA. Colorado Co-operative Fish and Wildlife Research Unit., Colorado State University.

Marsden, S.J. (1999) Estimation of parrot and hornbill densities using a point count distance sampling method. Ibis 141: 377-390.

Robinson Dean, J. (in prep.) Abundance, Range Size and Habitat Preferences in SE Sulawesi Birds and Butterflies. Operation Wallacea Report.