Multiscale and multivariate analyses for assessing psittacine nesting susceptibility to predation: an example from Yellow-shouldered Parrots (Amazona barbadensis)

作者：Sanz Virginia^*

来源：Ornitologia Neotropical, 2008, 19: 123-134.

• Cotorra Cabeciamarilla
• Amazona barbadensis
• Margarita Island
• multiscalar
• nest predation
• nest characteristics
• Venezuela
• Yellow-shouldered Parrot

Predation is the main natural factor reducing breeding success of the Amazona barbadensis population on Margarita Island (Venezuela). The objective of this study was to determine the nest characteristics most closely related to predation by conducting a multivariate analysis considering variables at different spatial scales. I expected that nests with higher entrances, deeper cavities, no branches below the entrance, and higher density of surrounding and canopy vegetation, would have lower predation rates. The following variables were considered at nest characteristics (entrance height, nest depth, height of the first branch under the nest entrance, canopy and horizontal cover), macrohabitat (patch size, patch shape complexity index), and landscape scales (percentages and number of different kinds of vegetation in a circle of 100-m radius around the nest). Parrot nests (n = 51) were classified in different categories depending on their predation rate during 10 years of study (1990-1999). Principal component analyses (PCA) were done at different spatial scales and the ones showing specific trends were then analyzed with ANOVA, using principal component 1 as the dependent variable. Nests with the highest predation rates had lower entrances, lower branches under the entrance, and less canopy cover compared with nests with no predation. Also, they were in smaller vegetation patches, with smaller extension of riparian vegetation cover and more types of vegetation around them. The study suggests that, in this species, predation is affected by variables at a larger spatial scale than those traditionally measured at the microhabitat level. The former should be considered for nests management, either natural or artificial.

• 出版日期2008