Density estimates, microhabitat selection, and foraging behaviour of the endemic blue chaffinch Fringilla teydae teydae on Tenerife (Canary Islands)

Aims: The main aim of this study was to present density estimates in good habitat for the Blue Chaffinch on Tenerife. At the same time other ecological aspects were studied, i.e. microhabitat selection and foraging behaviour.

Location: Seven study areas located around the pine forest of Tenerife, Canary Islands.

Methods: Point counts were used for censusing birds. Data were analysed with the DISTANCE software programs using an average detectability function. Microhabitat structure was characterized by measuring I I variables in a 25m radius at each point. We used Poisson regression models to predict counts for Blue Chaffinch from habitat measurements. Repeated standardised focal samples were used to record the foraging behaviour of Blue Chaffinch (one record per bird). Differences in foraging behaviour were analysed by chi-square tests.

Results: Based on the 370 point counts giving similar densities for the two main pine forest habitats for the species (6.7 birds/ha in the north vs. 6.5 birds/ha in the south). The density of thin pine trees best predicted Blue Chaffinch counts on the whole island. Chaffinch density increased significantly in the north of Tenerife as the shrub cover of A denocarpus sp. increased and as the mean height of the shrub layer increased. Finches were observed foraging mainly for Myrica faya seeds during the non-breeding (winter) season and on open cones for their seeds of the Canary Pine trees (Pinus canariensis) during nesting (females searching on the needles during this time), at least on the eastern side of the island where the sample protocol was undertaken.

Conclusions: This study justifies a forest management policy of selective clearing of heavily dense areas of pine trees in the north of Tenerife, where no undergrowth is present. Reafforestation campaigns in the south of this island should aim to plant with pine trees those areas which were historically dominated by pine trees.