Summer abundance and ecological distribution of passerines in native and exotic forests in São Miguel, Azores

Authors: Ricardo CEIA, Rúben HELENO and Jaime A. RAMOS

E-mail: ricardoceia@gmail.com

Published: Volume 56(1), June 2009. Pages 25-39.

Language: Spanish

Original Title: Abundancia estival y distribución ecológica de los passeriformes en el bosque autóctono y exótico de San Miguel, Azores

Keywords: ecological densities, exotic forest, laurel forest, Macaronesia, mist-netting, oceanic islands, Pyrrhula murina and point-counts.

Summary:

Aims:To assess the influence of native and exotic forests on the ecological distribution and abundance of forest bird species on São Miguel Island, Azores, during the breeding season.

Location: Forests in the eastern part of São Miguel Island, Azores.

Methods: Point-counts were conducted in two exotic forest habitats (copses of Pittosporum undulatum and plantations of Cryptomeria japonica) and in the native laurel forest. Program DISTANCE was used to estimate ecological densities (birds/ha) for five bird species per forest type. Mist-netting was carried out to assess the relative abundance of birds in four plots representing different altitudes and a gradient of infestation by exotic plants.

Results: Nine bird species were recorded during the point-counts, and six of them occurred in the three forest types. Goldcrest Regulus regulus azoricus was the most generalist and abundant species in all forest types and the endemic Azores bullfinch Pyrrhula murina the most specialist, occurring only in native forest. Both point counts and mist-netting showed higher diversity and equitability in areas/plots with native forest, although species richness was not higher than in exotic forests. Mist-netting results showed highest diversity and equitability in the mid-altitude native forest plot.

Conclusions: Birds showed a higher relative abundance in native than in exotic forests. Goldcrest was the most abundant species in C. japonica forest whereas the distribution of the Azores bullfinch was heavily restricted by the spread of exotic forest. This study demonstrates the importance of the native forest, particularly at mid altitudes, for the maintenance of a more homogeneous bird distribution in SÁ£o Miguel Island, Azores.

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