Effect of forest logging on food availability, suitable nesting habitat, nest density and spatial pattern of a Neotropical parrot

Abstract

Secondary cavity nesters, bird species that rely on the presence of existing cavities, are highly vulnerable to anthropogenic and stochastic processes that reduce the availability of cavity bearing trees. The most common logging practice in Neotropical forests is selective logging, where a few valuable tree species are logged, primarily old, large trees that are the most prone to develop cavities and produce larger amounts of fruits and seeds. Tucuman Amazon, Amazona tucumana, is a threatened parrot that relies on the tree-cavities and food provided by large, old trees. Our objective was to evaluate how logging affects 1) stand and nest plot forest structure, 2) nesting site selection, 3) food availability, 4) density of suitable cavities, 5) nest density, and 6) nest spatial pattern of Tucuman Amazon by comparing a mature undisturbed forest in a National Park (NP) vs a logged forest (LF). We determined the availability of suitable cavities and food resources consumed by Tucuman Amazon, and we compared nest density and spatial pattern of nests between NP vs LF. The Index of food availability for all tree species consumed by Tucuman Amazon and for P. parlatorei were significantly higher in NP than in LF (34.5 ± 13.3 m ha−1 vs. 3.5 ± 1.0 m ha−1 and 5.6 ± 2.3 m ha−1 vs. 1.2 ± 1.0 m ha−1, respectively). Density of suitable cavities for nesting in the NP was significantly higher than in the LF: 4.6 cavities ha−1 [C.I. 95 %: 3.07 – 7.04 cavities ha−1] vs. 1.1 cavities ha−1 [C.I. 95 %: 0.73 – 1.66 cavities ha−1], respectively. Mean density of Tucuman Amazon nests was significantly higher in the NP than in LF (0.25 ± 0.04 vs. 0.06 ± 0.04 nest ha−1, respectively). Food availability is an important factor that affects Tucuman Amazon populations and when food is not limiting, the availability of suitable cavities and territorial behavior could play a role in regulating nest density. When evaluating the limiting factors for secondary cavity-nesting species of conservation concern it is important to evaluate the interplay of a set of potential limiting factors to propose sound forest management recommendations.