Philip D. Round

A Field Test of Distance Sampling Methods for a Tropical Forest Bird Community

ABSTRACT. Distance sampling is usually preferred over uncorrected point counts for surveys of forest birds, but rarely has its accuracy been assessed against known numbers, particularly in tropical forests. We compared density estimates of eight species of breeding bird—Black-naped Monarch (Hypothymis azurea), Hill Blue Flycatcher (Cyornis banyumas), White-rumped Shama (Copsychus malabaricus), Puff-throated Bulbul (Alophoixus pallidus), Abbotts Babbler (Malacocincla abbotti), Puff-throated Babbler (Pellorneum ruficeps), White-browed Scimitar Babbler (Pomatorhinus schisticeps), and White-bellied Yuhina (Yuhina zantholeuca)—obtained through color-banding, nest finding, and territory mapping with those derived from distance methods in evergreen forest in northeastern Thailand. We also assessed the availability of birds to be detected using a closed-capture model and incorporated this with point-transect distance sampling. Abundance estimates from territory mapping and distance sampling were highly correlated, but biased for two species using line transects and five species using point transects. Six of the seven biased estimates were biased low. Probabilities of detection were not significantly different between lines and points, and there was no significant difference in the overall accuracy between methods. Accounting for observer differences improved density estimates but reduced precision. The variance in accuracy was mostly related to the behavior of the different species. Adjusting for availability did not improve the overall accuracy of the estimates, because of the low singing rates of tropical birds. Nonetheless, distance sampling provided relatively robust estimates despite the near total dependence on aural cues. Violations of distance-sampling assumptions may be frequent in heavily forested habitats, where both availability for detection and probability of detection on the transect line (or point) are likely to be <1.

A comparison of bird communities in mixed fruit orchards and natural forest at Khao Luang, southern Thailand

The avifauna of a mixed fruit orchard and nearby isolated forest patch on the mountain of Khao Luang, southern Thailand, was compared with that in natural forest. The orchard was about 75% as rich in bird species as the forest and was dominated by smaller frugivores, nectarivores and widespread generalists. Sundaic birds contributed 26% of sightings in the orchard, and understorey insectivores were poorly represented. The avifauna of the 4.5-ha forest patch was similarly depauperate and bore greater resemblance to that in the orchard than to that in forest. These results have implications for management since increasing emphasis is being placed upon the rights of local communities to manage and exploit resources in protected areas. While agricultural diversification may assist in restoring modest levels of diversity in areas already degraded or committed to human use, it should not be seen as a substitute for conventional protection of forest and wildlife through exclusion of such use.

A NEW BUSH-WARBLER (SYLVIIDAE, BRADYPTERUS) FROM TAIWAN

Abstract A bush-warbler of the genus Bradypterus, known from the mountains of Taiwan since 1917, has never been formally named as a distinct taxon. Songs of the Taiwan population differ strikingly from those of its Asian congeners in being much clearer, sweeter, more piercing, and in having a very different structure of elements. Several subtle but consistent morphological differences exist between specimens from Taiwan and all named taxa, principally in bill size and shape, plumage color and reduced variability, pattern of undertail coverts, and wing formula. Therefore, the Taiwan population is best treated as a new species.

The waterbird populations of three Welsh rivers

The composition of a riparian avifauna can vary considerably between the head-waters and lower reaches of a river. What are the physical features that influence the distributions of particular species?

Inland feeding by brent geese branta bernicla in Sussex, England

Abstract The numbers and pattern of distribution of dark-bellied brent geese Branta b. bernicla feeding inland around Chichester and Pagham Harbours, West Sussex in winter 1979/80 are described. A maximum of 11,000 birds fed inland. Taking the winter as a whole, 70% fed within 200 m of the coast. 68% of inland-feeding birds occurred on grass. This was partly influenced by deliberate scaring of the geese from cereals. 14% of the available area of grass around Chichester was used by geese but only 6% was heavily grazed. Of the area of cereals, 13% was used with 4% heavily grazed. Unless disturbed, the brent geese usually remained inland for most of the day, regardless of the state of the tide, returning to roost overnight on intertidal areas. The more uniformly distributed food supply in fields enabled the geese to feed in larger, more compact flocks than they could do on the estuary. The provision of grassland refuges is suggested as a means of alleviating conflict with agriculture. For Chichester Harbour up to five refuge areas may be required where the geese can feed undisturbed. Each refuge should not only provide the food requirements of the geese but be large enough to provide a buffer against human disturbance on surrounding land. The total refuge area should probably be not less than about 400 ha, on which many of the normal farming practices can continue. Refuges should be situated adjacent to the coast and the grass sward needs to be closely grazed by livestock or mown in the summer to provide a suitable short sward for the wintering geese.

Habitat use, moult and biometrics in the Manchurian Reed Warbler Acrocephalus tangorum wintering in Thailand

Manchurian Reed Warblers Acrocephalus tangorum wintering at Khao Sam Roi Yot, Thailand, were largely restricted to mature Phragmites reeds. The mean wing length (± sd) of 105 Manchurian Reed Warblers was 54.5 ± 1.41 mm. There was no evidence of differences in body weight in spring, autumn or winter. Both adults and first‐winter birds underwent a complete moult soon after arrival in their winter quarters. Primary moult duration was estimated to be 59 days. Moult of secondaries was suspended in approximately one‐third to one‐fifth of birds, the few retained, old, unmoulted feathers usually being replaced later in the winter. No further moult was usually detected prior to northward spring migration.

Moult of primaries in Long-toed Stints (Calidris subminuta) at a non-breeding area in Thailand

Adult Long-toed Stints Calidris subminuta, spending the non-breeding season at a coastal fresh to brackish water site in central Thailand, commenced moult of primaries soon after their arrival from their breeding grounds. The estimated duration of primary moult was 70 days, with starting and completion dates 14 August (standard deviation ± 13.3 days) and 23 October. Juvenile/first-year birds did not moult any flight feathers during the 1 July to 31 December study period. The adaptive significance of this rapid moult of flight feathers is probably linked to the influence of monsoon upon food abundance. Birds underwent a rapid moult of flight feathers towards the end of the southwest monsoon (wet season), when food was most abundant, and completed their moult before the onset of the dry season caused many wetland habitats to dry up.

Diet and Breeding Biology of Asian Golden Weaver (Ploceus hypoxanthus)

The Asian Golden Weaver ( Ploceus hypoxanthus ) occurs in Myanmar, Thailand, Laos, Vietnam, Cambodia, and Indonesia and inhabits marshes, grasslands, reeds and rice fields close to water in the lowlands (Robson 2000) and natural waterholes in lowland dry dipterocarp forest (Round 1998). It is globally ‘Near-threatened’ due to habitat loss through the conversion of wetlands to agricultural and settlement areas (BirdLife International 2007). In Thailand it is local and uncommon in the north, north-east and central regions (Lekagul and Round 1991, Robson 2000). However, no quantitative data are available regarding its ecological requirements. Our objectives were to collect basic ecological data on: i) population structure, ii) nesting habitat characteristics, iii) food selection and foraging behaviour, and iv) parental care at the nest.

Habitat Association and Conservation Status of the Endangered Giant Nuthatch (Sitta magna) in Thailand

The Giant Nuthatch Sitta magna is restricted to southwestern China, eastern Myanmar, and northern Thailand. Although globally endangered, most aspects of its ecology remain as yet unquantified. To assess its habitat associations and population size, we conducted point counts with playback at 42 sample points across 12 discrete historical and potential localities within its Thai range during October to November 2015. Eleven habitat variables were measured, including three site-level vegetation variables and eight landscape variables were assessed, using geographic information system land cover maps. N-mixture models were applied to estimate density and extrapolate the size of the population. The Giant Nuthatch was found at four localities (12 of the 42 sample points) at elevations between 1,192 m and 1,738 m. It was not detected at four historical Giant Nuthatch localities in protected areas. Abundance increased with increasing elevation, increasing proportion of evergreen forest, and greater distance from villages. We estimated that the Thai population of Giant Nuthatch was approximately 964 individuals based on an average density of 1.96 individuals/km2 in approximately 491.8 km2 of appropriate forest habitat at 1,192 m to 1,951 m elevation. This may be an overestimate because available forest cover maps and images do not distinguish between the characteristic, patchily distributed, lower montane open pine–oak forest association used by Giant Nuthatch and denser, closed-canopy forest. Although Thailand’s Giant Nuthatch population may be better protected than those in adjoining countries, we suggest that it remains threatened by forest fragmentation and habitat degradation throughout its range. Further comprehensive research is needed to assess the status of the remaining global population and the reasons for its scarcity.

Incidental impacts from major road construction on one of Asia’s most important wetlands: the Inner Gulf of Thailand

Large-scale infrastructure development projects can have devastating impacts upon biodiversity. We investigated the impacts of roads on land-use change in a coastal area of South-east Asia, an area of high biodiversity subject to intense human pressure. The objectives of this study were (1) to examine impacts of major roads on rates of land-use change and habitat conversion in and around the Inner Gulf of Thailand, a large wetland of international importance; and (2) to evaluate the conversion rate of salt-pans (a critical habitat for several species of threatened shorebirds) between 1990 and 2011. Nine land-use types were categorised into two groups: seminatural and human-dominated. Proportions of each land-use type at different distances from major roads were determined using GIS data. More than 40% of the area was used for aquaculture during the entire study period. The amount of seminatural habitats was positively correlated with distance from major roads. Agriculture and urban areas showed the greatest changes in area (decreasing and increasing, respectively). Habitats that changed from seminatural to human-dominated were negatively correlated with distance from major roads. Most of the converted salt-pans were lost to aquaculture. To protect important wetlands from further biodiversity loss: (1) new major road construction should be avoided or minimised; and (2) land-use strategies that both satisfy short-term human needs and maintain ecosystem capacity to provide services in the long term should be adopted.