Subsidient: Louise Franssen / Wageningen University
Subsidy: S183.65

The Neotropical region comprises the highest diversity of cavity nesting birds on Earth. However, habitat loss and forest degradation are restricting their existence. The aim of this study was to investigate the drivers of the availability of suitable tree cavities for secondary cavity nesters in four landscape types in Ecuador. Per landscape type, six transects of 25 x 100 m were established. Along these transects, I searched for and subsequently assessed cavity and tree characteristics. In addition, I established three subplots of 10x10m in the transects in which I studied forest structure and tree diversity. I found that primary had the highest densities of suitable cavities (4.7/ha), followed by secondary forests (3.3/ha). Fewer cavities were present in chakras, an agroforestry system, (2.7/ha) while I found no cavities in cacao monocultures. The majority of cavities in my study area were formed by decay-related processes, as only 7% of the suitable cavities was produced by woodpeckers. Decay-formed cavities were found in trees that were significantly larger than trees with an excavated cavity. Most cavities (53%) were found in dead trees, although only 9% of all studies trees was dead. Therefore, the key drivers for tree cavity formation in my study area are decay processes and the availability of relatively large trees. Consequently, conservations priorities should focus on the preservation of large trees and mature forests.