David Palomino

Birds on novel island environments. A case study with the urban avifauna of Tenerife (Canary Islands)

We analyzed the variation in island bird communities of urban environments related to habitat characteristics, using regression/classification tree analyses. Data from field censuses in cities/towns representing the urban heterogeneity of the whole island were obtained in Tenerife (Canary Islands, Spain). Urban bird abundance in Tenerife was negatively affected by altitude and the cover of dry Euphorbia shrubs and positively influenced by the height and cover of the tree layer. Species richness was negatively associated with building cover and positively related to tree height and altitude. Data from field censuses in Tenerife were compared with that of similar urban environments in the mainland (Madrid Province, central Spain). Species diversity was higher in the urban sample of Tenerife than in that of Madrid and the proportion of bird species from the regional pool ‘captured’ by urban environments was higher in the island than in the mainland. Nine native species and three alien species were more abundant in island urban environments than in the continent (densities, at least, 100% higher), the converse occurring for only five species. At a biogeographic scale, we conclude that the avifauna of Tenerife Island is more prone to occupy a new artificial environment than the mainland bird fauna of central Spain.

Population size and habitat relationships of Black-bellied Sandgrouse Pterocles orientalis in the Canary Islands, Spain

Summary We estimated the breeding population size and assess the habitat relationships of Black-bellied Sandgrouse in the Eastern Canary Islands (Fuerteventura, Lanzarote and La Graciosa, Spain) by means of a survey based on 1,787 0.5-km line transects and distance sampling done in 2005 and 2006. The population comprised 2,906 individuals (90% CI: 2,363–3,562), which is much higher than the numbers estimated in previous reports based on partial surveys, and constitutes 20 %o f the total Spanish population. Sandgrouse in the Canaries are currently restricted to Fuerteventura, where 70% of the population gathers in four areas that encompass just 16.7 % of the island and are largely within Special Protection Areas classified under the EU Birds Directive (except the area of Tefia-Ampuyenta, first in absolute number of individuals). The environmental characteristics that maximize the probability of occurrence of the sandgrouse in Fuerteventura (probability 5 0.196) are: treeless non-cultivated areas of sandy soils without bare bedrock, with a rock cover less than 44%, located in non-coastal areas with an average terrain slope less than 27.5%, at more than 400 m from the nearest urban area, with less than 795 m of dirt roads per 20 ha, with at least 0.9% of shrub cover and a NDVI index higher than 53. Sandgrouse were closer to human settlements in midsummer than in March, perhaps being attracted to artificial pools surrounding villages. Similar habitat characteristics exist in nearby Lanzarote, where the species could hypothetically reach densities as high as 4–5 birds km 2 . Possible reasons for the absence of sandgrouse in this island are discussed.

Distribution of Azure-winged Magpies Cyanopica cooki in Spain: both local and large-scale factors considered

Abstract. Although the main environmental determinants of bird distribution are contingent on the spatial scale of studies, the consistency of species distributional patterns has rarely been considered in large- and local-scale analyses. The competing roles of biotic, abiotic and landscape features in shaping the distribution of Azure-winged Magpies were assessed at two spatial scales: a large-scale analysis of 50×50 km blocks across nearly the whole of the species range (the Iberian Peninsula), and a small-scale assessment based on point counts of 50-m radius located near the northern edge of its distribution. The observed species distribution can be explained mainly by geographic and climatic features whereas the influence of landscape factors is weak. Azure-winged Magpies are more abundant near the core of its range in southwest Iberia and rarify towards the north and the east, in what seems to be a limitation of their ability to tolerate colder and drier climates, respectively. At local level, Azure-winged Magpies are habitat generalists avoiding urban sprawl whose probability of occurrence decreases with elevation, reaching zero above 1,600 m a.s.l. The species prefer wooded environments, although it tends to avoid mature, dense forests. The occurrence of potential competitors (Common Magpie Pica pica and Jay Garrulus glandarius), whose habitat preferences widely overlap with those of the Azure-winged Magpie, had no influence on either the large-scale or local distribution of Azure-winged Magpies. From a conservationist standpoint, the presence of the species in agricultural, pseudosteppe habitats with thinly forested watercourses highlights the importance of conserving gallery forests in the regions less suitable for the species.

Preferred temperature and thermal breadth of birds wintering in peninsular Spain - the limited effect of temperature on species distribution

Background. The availability of environmental energy, as measured by temperature, is expected to limit the abundance and distribution of endotherms wintering at temperate latitudes. A prediction of this hypothesis is that birds should attain their highest abundances in warmer areas. However, there may be a spatial mismatch between species preferred habitats and species preferred temperatures, so some species might end-up wintering in sub-optimal thermal environments. Methods. We model the influence of minimum winter temperature on the relative abundance of 106 terrestrial bird species wintering in peninsular Spain, at 10 ×10 km2 resolution, using 95%-quantile regressions. We analyze general trends across species on the shape of the response curves, the environmental preferred temperature (at which the species abundance is maximized), the mean temperature in the area of distribution and the thermal breadth (area under the abundance-temperature curve). Results. Temperature explains a low proportion of variation in abundance. The most significant effect is on limiting the maximum potential abundance of species. Considering this upper-limit response, there is a large interspecific variability on the thermal preferences and specialization of species. Overall, there is a preponderance of positive relationships between species abundance and temperature; on average, species attain their maximum abundances in areas 1.9 °C warmer than the average temperature available in peninsular Spain. The mean temperature in the area of distribution is lower than the thermal preferences of the species. Discussion. Many species prefer the warmest areas to overwinter, which suggests that temperature imposes important restrictions to birds wintering in the Iberian Peninsula. However, one third of species overwinter in locations colder than their thermal preferences, probably reflecting the interaction between habitat and thermal requirements. There is a high inter-specific variation in the versatility of species using the available thermal space, and the limited effect of temperature highlights the role of other environmental factors determining species abundance.