Nest Predation Risk on Ground and Shrub Nests in Forest Margin Areas of Sulawesi, Indonesia

Abstract

Forest loss and fragmentation in Indonesia may seriously affect the survivorship of forest birds and lead to local extinction of bird populations. We used 786 artificial nests baited with quail eggs to examine the effect of habitat alteration on nest predation in Lore Lindu National Park, Sulawesi. Natural forest and four habitats of forest margin areas: forest edge, forest gardens, coffee plantations, and secondary forest, were studied. Two types of artificial nests, ground and shrub nests were placed in these habitats at two different locations for a period of 8 days. In addition, we used automatic cameras and cage-traps to identify the predators. Nests in shrubs experienced significantly higher predation rates in forest margin areas than in natural forest. Predation on ground nests did not differ significantly between these habitat types, but was significantly higher than that on shrub nests in each habitat except forest edge. Rodents were the most common predators of both nests, but shrub nests were also susceptible to Dwarf cuscus (Strigocuscus celebensis), squirrels, and tree snakes. The nest predation rates we found were among the highest found in tropical rainforests, probably a consequence of the unique predator assemblages of Sulawesi. These results suggest that egg survival is negatively affected by human intervention and that human-induced habitats might have only limited importance for the conservation of Sulawesi's largely endemic understorey avifauna. These considerations might be important since forest margins comprise significant proportions of protected areas on Sulawesi and play an important role in future Park zoning concepts as well as in conservation-oriented land use management.

Ground nest predation might not be higher along edges of Neotropical forest remnants surrounded by pastures: evidence from the Brazilian Atlantic forest

“…The results here found corroborate other studies in Tropical forest areas (Arango-Vélez and Kattan 1997; Carlson and Hartman 2001;Pangau-Adam et al 2006), suggesting that potential nest predators are not proceeding from the surrounding matrix. If that wasnЈt the case, one might expect diVerences between internal and external edges, with higher nest predation rates occurring in external edges rather than in internal edges or in the forest interior.…”

“…This argument is fundamentally based in the assumption, which is beginning to be debunked (Lahti 2001;Hausmann et al 2005), that generalist predators coming from the disturbed matrix are responsible for the increase in predation in the contact zone between the matrix and the original forest (Andrén and Angelstam 1988). Quite the contrary, the results here found do corroborate other experiments carried out in the Atlantic Forest (Leite and Marini 1999;Duca et al 2001) and in other Tropical areas (Arango-Vélez and Kattan 1997;Wong et al 1998;Matthews et al 1999;Hausmann et al 2005;Pangau-Adam et al 2006), which did not Wnd signiWcant edge eVects in nest predation or in avian reproductive success (Lahti 2001). In the case of the few experiments already carried out in the Atlantic forest, the observed absence of edge eVect was due to the small size of studied fragments [2-174 ha in Leite and Marini (1999) and 1 to 330 ha in Duca et al (2001)].…”

“…In another major recent revision Batáry and Báldi (2004) concluded that there is an increase in nest predation near fragment edges, however most data come from temperate areas. In fact, studies carried out in tropical forests indicate that nest predation rates might be not higher near edges than in least disturbed forest interior (Arango-Vélez and Kattan 1997;Carlson and Hartman 2001;Duca et al 2001;Hausmann et al 2005, Pangau-Adam et al 2006. Therefore, generalizations from experiments conducted in temperate areas might not be mirrored in tropical areas.…”

“…The diVerences can be related to several factors, among them, the diVering predator sets acting in these regions (Gibbs 1991;Pangau-Adam et al 2006). Söderström (1999) stressed, for example, that mammals can have a relatively larger role as nest predators in tropical forests than in temperate regions.…”

“…Considering that the relationship between edge eVect and ground nest predation in Tropical forests in general (Gibbs 1991;Piper and Caterall 2004;Pangau-Adam et al 2006) and in the Atlantic forest in particular is far from well resolved, the present paper aims to investigate the following questions: (i) Is ground nest predation higher near edges than in the interior of the forest? (ii) Is nest predation diVerent between seasons, periods (day £ night) and edge types (internal £ external edges)?…”