Moratoria on international trade are frequently used to protect threatened species but few studies have examined their effectiveness in allowing populations to recover. We present population data collected before and after a moratorium on trade in the citron-crested cockatoo Cacatua sulphurea citrinocristata, a distinctive subspecies of the yellow-crested cockatoo endemic to Sumba, Indonesia. Before legal trade ceased in 1993 numbers of cockatoos leaving Sumba averaged c. 1,600 per year, and the 1992 population, estimated at 3,200, surely could not sustain such a level of trade. We surveyed cockatoos in four forest patches on Sumba in 1992, and then surveyed these same forest patches 10 years later, using the same field methods. Forest cover within the four patches was similar between years. We recorded a statistically significant increase in overall cockatoo density, from c. 2 birds per km2 in 1992 to >4 per km2 in 2002. Group sizes were also larger in 2002 than in 1992. Densities at two forest sites had increased considerably, at another the population was stable, but at one small forest patch a small population in 1992 had probably decreased. While the population has made a modest recovery, densities remain low compared to cockatoo populations elsewhere. Illegal trade is known to persist and its volume should be monitored closely.

We studied nest-site selection and nesting success in the critically endangered Yellow-crested Cockatoo Cacatua sulphurea throughout a breeding season in Manupeu-Tanadaru National Park, Sumba. Within a 6 km 2 study area, which supported about 60 birds, cockatoos displayed disproportionate interest in cavities in trees containing other active nests, and cavities already actually occupied by parrots or owls. Actual nesting attempts were made at only eight cavities, and a single chick fledged. Interspecific interactions were observed at every one of these nests. Breeding activity was negatively correlated with monthly rainfall, which was the heaviest for at least 10 years, and it is possible that adverse weather conditions disrupted cockatoo nesting this season. Whether this is the case or not, our study shows how low reproductive output can be in the species and this has serious implications for survival of the population on Sumba.

SummaryWe assessed the impact of forest fire on the nesting success of the endemic Red-knobbed Hornbill Aceros cassidix in north Sulawesi, Indonesia. Pre-and post-fire breeding activity was monitored at 60 nest trees. Low rainfall and possible reductions in fruit abundance did not appear to have an effect on initial nest uptake or on subsequent chick production at non-burnt nests, which were comparable to previous years. However, there was an adverse effect on productivity at nests that directly experienced fire and the accompanying heat and smoke in the vicinity, resulting in a post-fire nest success (62%) that was significantly lower than in previous years (78.6-80%). Population recruitment dropped by an estimated 47% to 0.17 fledglings/breeding pair. Our data suggest that, given the reproductive profile of this species and the ability of fire to reinforce its own negative effects on forest habitats, Red-knobbed Hornbill populations may be vulnerable to the potential effects of repeated fires.

Nest‐site characteristics of two hornbill species, the Red‐knobbed Hornbill Aceros cassidix and the Sulawesi Dwarf Hornbill Penelopides exarhatus, are presented and compared at two sites in north Sulawesi, Indonesia. Seventy‐four Red‐knobbed Hornbill and 12 Sulawesi Dwarf Hornbill nests were located. Sulawesi Dwarf Hornbill nests were at lower densities and more evenly spaced than Red‐knobbed Hornbill nests. Although selective, neither species appeared to be nest‐site limited, except perhaps for the Red‐knobbed Hornbill in hill forest. Principal components analysis indicated that Red‐knobbed Hornbills were ‘catholic’ in their preferences, although nests were generally in tall, mature specimens of large girth, located high and in the upper half of the tree. The Sulawesi Dwarf Hornbill nested exclusively in live trees and nests were on average located half way up in tall canopy trees with large girths. Within certain parameters, both species were flexible with respect to their nest cavity size and shape requirements; Red‐knobbed Hornbills choose sites with larger entrances and internal dimensions. Discriminant function analysis produced parsimonious models for each site, with high rates of correct classification, based on structural, floristic and breeding success parameters. Lack of transference of predictive powers of the models between sites demonstrates the apparent variability in hornbill nesting behaviour and indicates the need for caution when extrapolating models to other sites. Possible factors affecting the nesting density and distribution of each hornbill species are discussed.

SummaryDensities and population estimates are presented for the little known Yellow-breasted Racquet-tail Parrot Prioniturus flavicans, a species endemic to the Indonesian island of Sulawesi. Sixteen months of fieldwork was conducted within two protected areas in the island's northern peninsula. Densities were found to be much greater in the Bogani Nani Wartabone National Park than in the Tangkoko Duasaudara Nature Reserve: 16.27 and 7.18 birds/km 2 , respectively. The species has a much more restricted range than previously thought, being confined to the eastern two-thirds of the north peninsula. The remaining suitable habitat within this range, lowland rainforest, is estimated to be c. 11,300 km 2 . Using this figure in conjunction with density values we estimate that the world population for this species may be greater than 44,650 birds. Whilst such a population size is higher than previously thought, the very restricted distribution of the species causes concern for its future as loss and fragmentation of forest habitat are ongoing within its range.