Eduardo de Juana

Surveys of wintering Little Bustards Tetrax tetrax in central Spain: distribution and population estimates at a regional scale

Developing a standardized survey methodology to census and estimate the size of wintering populations is a main conservation priority for the endangered Little Bustard. We present a standard and repeatable methodology to census wintering Little Bustard populations at a regional scale, and the first statistically reliable population estimate of a Little Bustard wintering population in Spain. We carried out two surveys, in 2003 and 2004, using UTM 10 km 6 10 km squares as census units, which were subjected to stratified sampling over the species’ potential distribution range in the region of Madrid (Central Spain). Only the areas of potentially suitable habitat within squares of known winter presence of the species were considered. The species’ winter distribution in Madrid was fairly constant between years, showing a fragmented pattern in three main nuclei. The number of Little Bustards observed was consistent between surveys (752 and 786 birds, respectively), with birds grouped in an average of 32 flocks (1 to 350 birds, mean 5 27.9 birds). No between-winter differences in flock size were observed, although differences between sectors were significant. The highest densities were observed in the Tagus valley (mean density 5 2.9 birds km, 293 birds), followed by north-eastern farmland (mean density 5 0.6 bird km, 269 birds). The estimated size of the Little Bustard population wintering in the Madrid region was 1,051 (95% CI 5 1,043–1,231). This calculation was based on recorded population density, measured as the number of birds per square kilometre, and considers the potential habitats available in each sector. We propose this methodology as adequate for surveying any Little Bustard wintering area, at both regional and smaller spatial scales. Survey results are consistent with previous tentative estimates for the region of Madrid, and with available information on Little Bustard movements. Sixty-five per cent of squares with Little Bustard presence were outside any protected area, which makes the wintering Little Bustard population of Madrid highly vulnerable to habitat disappearance and may affect the viability of breeding nuclei whose individuals winter in the region.

Nombres en castellano de las aves del mundo recomendados por la Sociedad Española de Ornitología

Esta es la decimocuarta entrega de los nombres para las aves del mundo en castellano que propone la Sociedad Espanola de Ornitologia (SEO/BirdLife). Tiene su base en el volumen 14 del Handbook of the Birds of the World (Lynx Edicions, Barcelona), con las siguientes 17 familias del orden Passeriformes: Malaconotidae, Prionopidae, Vangidae, Dicruridae, Callaeidae, Notiomystidae, Grallinidae, Struthideidae, Artamidae, Cracticidae, Pityriaseidae, Ptilonorhynchidae, Paradiseidae, Corvidae, Buphagidae, Sturnidae y Passeridae. Estas familias agrupan un total de 468 especies. Como es habitual, la lista sigue en todos sus detalles la clasificacion y nomenclatura cientifica del mencionado Handbook of the Birds of the World. Las entregas anteriores de esta serie aparecen en Ardeola, 41(1): 79-89, 41(2): 183-191, 43(2): 231-238, 45(1): 87-96, 47(1): 123-130, 48(1): 107-110, 49(1): 121-125, 50(1): 103- 110, 51(2): 491-499, 52(2): 389-398, 54(1): 145-153, 56(1): 127-134 y 56(1): 135-142. En relacion a las especies de la avifauna espanola, cuando los nombres no coinciden con los de la Lista Patron de la Sociedad Espanola de Ornitologia (Ardeola, 1: 11-85), en un apartado final se explican de forma sucinta las razones que provocan tales cambios. Son seis especies de corvidos: Garrulus glandarius, Cyanopica cooki, Pica pica, Nucifraga caryocatactes, Corvus monedula y Corvus corax.

Migration Patterns of Iberian Little Bustards Tetrax tetrax

Summary. The term “migratory” refers to animals performing yearly round-trips between breeding grounds and post-breeding areas, whereas the term “sedentary” refers to those remaining the whole year in their breeding grounds. However, migration is a complex and varying phenomenon governed by genetic and environmental factors, particularly in species with wide distribution ranges. Here we describe and classify the seasonal movement patterns of 71 little bustards Tetrax tetrax, an endangered Palearctic steppe bird, radio- and satellite-tracked in the Iberian Peninsula. Four major movement patterns were identified, with 89% of little bustards behaving as migrants, among which 75% (summer migrants and summer-winter migrants) performed their first movement after breeding during the summer (mainly between May and July), whereas 14% (winter migrants) left their breeding sites in autumn (mainly between September and November). The remaining 11% were strictly sedentary. On average, summer migration started on June 14th, and winter migration on October 3rd, while pre-breeding migration started on March 23rd. Summer migration occurred in most Iberian regions, although it was mainly found in semiarid Mesomediterranean areas. Winter migration occurred only in the northern half of the Peninsula, being the only pattern found in Subatlantic and highland areas. All winter migrants wintered in Thermomediterranean localities of southern Iberia. The sedentary pattern was found only in the Semiarid Mesomediterranean and Thermomediterranean sectors. This is a good example of complex intraspecific variation in the migratory behaviour of a species that occupies a diverse range of environments. The variability of movement patterns of Iberian little bustards is much greater than previously thought and should be taken into account in conservation programmes for the species.

Breeding bird species diversity across gradients of land use from forest to agriculture in Europe

Loss, fragmentation and decreasing quality of habitats have been proposed as major threats to biodiversity world-wide, but relatively little is known about biodiversity responses to multiple pressures, particularly at very large spatial scales. We evaluated the relative contributions of four landscape variables (habitat cover, diversity, fragmentation and productivity) in determining different components of avian diversity across Europe. We sampled breeding birds in multiple 1-km2 landscapes, from high forest cover to intensive agricultural land, in eight countries during 2001−02. We predicted that the total diversity would peak at intermediate levels of forest cover and fragmentation, and respond positively to increasing habitat diversity and productivity; forest and open-habitat specialists would show threshold conditions along gradients of forest cover and fragmentation, and respond positively to increasing habitat diversity and productivity; resident species would be more strongly impacted by forest cover and fragmentation than migratory species; and generalists and urban species would show weak responses. Measures of total diversity did not peak at intermediate levels of forest cover or fragmentation. Rarefaction-standardized species richness decreased marginally and linearly with increasing forest cover and increased non-linearly with productivity, whereas all measures increased linearly with increasing fragmentation and landscape diversity. Forest and openhabitat specialists responded approximately linearly to forest cover and also weakly to habitat diversity, fragmentation and productivity. Generalists and urban species responded weakly to the landscape variables, but some groups responded non-linearly to productivity and marginally to habitat diversity. Resident species were not consistently more sensitive than migratory species to any of the landscape variables. These findings are relevant to landscapes with relatively long histories of human land-use, and they highlight that habitat loss, fragmentation and habitat-type diversity must all be considered in land-use planning and landscape modeling of avian communities.

Bioassess bird data

Landscape variables and avian point-count species richness data collected in the BioAssess project 2001-2002 in eight European countries