Vanessa Walther


Nest predation in different woody structures of the Biological Corridor

La Gamba, Costa Rica

MSc Student
Advisor: Christian Schulze

Department of Botany and Biodiversity Research, University of Vienna


Rainforests are globally one of the most threatened habitats. They are greatly endangered by land use and global warming a.o., leading to habitat transformations which are in turn responsible for 85% of the endangered species world wide (Hald-Mortensen, 2023). Even though tropical rainforests are threatened, conservational efforts have been enabling secondary forests to expand in size (Wright, 2005). The La Gamba Biological Corridor in Costa Rica (province Puntarenas) is one of these secondary forests and is intended to promote the connectivity of existing old fragmented rainforest patches and to function as a stepping stone for various species to travel safely from one location to another within fragmented habitats (Seaman; Schulze, 2010). To understand the success of these conservational efforts, one of the key parameters to estimate population dynamics is the nest fate (Ball; Bayne, 2012). If most of the birds nests ware to be predated, for example, consequentially their breeding success would be very low and the environments would become sink habitats (Seaman; Schulze, 2010).

This future study will start in November 2024 and investigate the extent of bird nest predation in the understory layer in different habitats that can potentially be used by forest birds for breeding. This study further aims to uncover which predators play a decisive role there. The study sites for this research will be located around the La Gamba Tropical Station in old-, as well as, secondary- and gallery forests. Artificial nests with real quail eggs and cameras will be placed in the understory layer of the different locations. The gathered data will be analyzed and compared to show eventual correlations between the appearance of specific predators and forest types (e.g.). According to past general studies it is likely the nest predation will be connected to their distance from the forest edge (Seaman, Schulze, 2010; Valentine et al., 2019), as well as showing a decrease in general nest predation at locations with higher canopy coverage but an increased percentage in avian nest predators (Valentine et al., 2019). Specific nest predators, expected to be frequent to substantial bird nests predators, are cowbirds (Molothrus sp.), especially in gallery forests (Hoover et al., 2006 in: Seaman; Schulze, 2010), toucans (Ramphastidae sp.) (Cove et al., 2017), the collared aracari (Pteroglossus torquatus) (Cove et al., 2017) and bird snakes (Pseutes poecilonotus) (Visco; Sherry, 2015). Low numbers of Tayras (Eira Barbara), white-nosed coatis (Nasua narica), northern raccoons (Procyon lotor) and the common opossum (Didelphis opossum) have also been discovered as nest predators near a neighboring research station (Cove et al., 2014). The results of this study will better the understanding of the bird nest predator dynamics in the understory layer of different tropical rainforest habitats, as well as to estimate the value this layer of the habitats could hold as breeding ground.