Size matters: the effects of forest fragmentation and resource availability on the endemic Sumba Hornbill Aceros everetti

Abstract

We examined the influence of forest fragmentation and resource availability on the abundance and distribution of Sumba Hornbill Aceros everetti, a large, canopy-dwelling bird endemic to Sumba Island, Indonesia. Hornbill numbers were estimated monthly from August 1998 to September 1999. Estimates were made in three large (≥1,000 ha) and three small (<1,000 ha) forest fragments, using a standard line transect method. Phenological patterns of canopy trees were assessed in 10 × 50 m plots. Our data indicated that forest patch size may be a better predictor of Sumba Hornbill abundance and distribution than overall resource availability. Hornbills occurred at higher densities in large forests (6/km2) than small forests (2.4/km2). Small forests produced more fruit/ha per month but lacked a number of important hornbill food species. Monthly fruit availability in large and small forest fragments had no significant effect on fluctuations in hornbill density. However, hornbill densities were significantly higher in forests with high densities of strangling figs, after controlling for patch size, and in larger forests hornbill densities correlated with the abundance of ripe figs. We hypothesize that small patches still have conservation value if they are within hornbill ranging distance, and speculate that Sumba's forests are in a dynamic phase before the full impact of fragmentation has been expressed.

Does landscape structure affect resource tracking by avian frugivores in a fragmented Afrotropical forest?

“…Since search time (including flights among isolated trees) is believed to be cost-balanced against the relative award of the fruits (consistent with optimal foraging; Levey et al 1984), fruit preference and selection behaviour is dynamic and may vary in time and space, often in complex ways (Fleming et al 1977, Denslow et al 1986). is considered a key resource for hornbills (Kinnaird et al 1996, Sitompul et al 2004, Kirika et al 2008. Properly accounting for species-specific food preference therefore requires long-term foraging observations or analyses of faecal pellets.…”

“…Journal compilation # 2009 Ecography Subject Editor: Carsten Rahbek. habitat conversion, Sitompul et al 2004), environmental (e.g. For instance, adaptive tracking behaviour may be disrupted by anthropogenic (e.g.…”

“…social organisation: Tellería and Perez-Tris 2007; reproduction: Simon et al 2002) processes, each acting at similar or different spatial and temporal scales (Herrera 1998, García and Ortiz-Pulido 2004, Tellería et al 2005, Tellería and Perez-Tris 2007. Because fruit production is often larger in gaps, secondary forests and small forest fragments (Denslow et al 1986, Levey 1988, Sitompul et al 2004, fruit tracking may result in seemingly opposite effects of forest fragmentation on avian frugivore densities, i.e. If landscape connectivity, defined as the degree at which movements of animals and plants are facilitated (Taylor et al 1993), is high, tracking behaviour can be expected to result in synchronized fluctuations between frugivore activity and fruit production (Graham 2001, Levey et al 2005.…”

Dietary specialization and fruit availability among frugivorous birds on Sulawesi

“…1999). Within forest patches, fig abundance might directly influence frugivorous bird population densities (Sitompul et al . 2004).…”

The Distribution and Population of Wreathed Hornbill (Aceros Udulatus) in Mount Ungaran Central Java

“…What was more interesting is that there were found three active nests in Mount Gantong. The high crising range of Wreathed Hornbill, approximately 50 km each day, makes it possible for them to explore the whole area searching for foods [18], [19]. All kinds of Hornbills like ripe fruits and collectively they search for the food sources.…”