This study describes the climatic factors determining the distribution of two sympatric steppe birds, the little and the great bustards, on a Western Palearctic scale. We used the European Bird Census Council breeding bird atlas, recording presence/absence for 50×50 km UTM squares. Climate data were extracted from a 10′ latitude × longitude global compilation. Linear and quadratic terms were included to account for non-linear responses. A model-averaging approach was performed to determine the weight and effect of those variables describing the climatic preferences for each species. Although both showed a preference for drier areas in Europe, our results suggest that the great bustard's climate niche is mainly defined by variables related to primary production (e.g. rainfall, soil moisture), with temperature-related variables being less influential. These results contrast with those for the little bustard, whose climate niche seems to be defined by both temperature and precipitation-related variables (e.g. annual rainfall, temperature range). Our analyses detected significant non-linear responses of presence/absence of both species to some climate variables: great bustard with precipitation and spring temperature; little bustard with temperature range, precipitation and soil moisture index. This study shows the reliability of model-averaging methodology for describing the climatic niches of species.

The timing of egg laying is a critical event for the fitness of birds because to a large extent it determines their reproductive success. The effects of weather conditions and climate on the onset of reproduction have been widely studied over recent decades and an advance in the timing of breeding phenology has been confirmed in many species. We explored the variation in the timing of the onset of breeding in a Cantabrian population of European shags over the past decade. The results demonstrate that the laying date of this population has advanced by almost 40 days in only 10 years. This advance in the timing of breeding coincides with the global warming trend detected in the last century. However, of the climatic variables studied, only the temperature anomaly index showed a positive correlation with laying date, whereas the effects of the NAO index and SST were negligible, suggesting that local conditions have a much more important effect on this population than large-scale climate change.

Iberia offers one of the last opportunities four migrants to refuel before crossing the Sahara. It is also a destination for populations that overwinter within the circum-Mediterranean region. Our aim was to analyse whether two bluethroat subspecies that stop over in northern Iberia and face different migration distances, show different stopover behaviour in terms of periods of passage, fuel management and stopover duration. The subspecies were Luscinia svecica namnetum, which overwinters within the circum-Mediterranean region; and L. s. cyanecula, some of which migrate to tropical Africa. Overall, we obtained 265 captures, involving 208 distinct bluethroats and 56 recaptures, at the Txingudi marshlands in northern Iberia, during the autumn migration periods of 2007 and 2008. Passage periods did not differ between both subspecies, nor did fuel load (body mass: 15.0 g; fat: 1.0), mass deposition rate (0.07 g/day) and stopover duration (15.3 days). However, late L. s. cyanecula showed higher fuel loads than early individuals, so these birds could potentially cover longer distances without needing to refuel. Mean fat score was low for both subspecies which, together with the very low rate of fuel accumulation, supports the hypothesis that Iberia is crossed in consecutive short steps. Long-distance L. s. cyanecula migrants could acquire the high fuel loads needed to migrate to tropical Africa in southern Iberia or north-western Africa.

In order to test biometrics and plumage variability in bluethroats Luscinia svecica in central Iberia, 185 birds were captured in four areas (Sierra-Béjar, Sierra-Piedrahita, Sierra-Gredos and Sierra-Paramera). Older bluethroats were significantly larger than second calendar year birds in wing, tail, and total body lengths, but not in tarsus and bill lengths. A multivariate analysis of variance (MANOVA) and a principal component analysis (PCA) were used. Total body length only varied significantly between sampling areas: the birds from Sierra-Béjar were larger than those from Sierra-Gredos and Sierra-Paramera, but were similar to those of Sierra-Piedrahita. Birds with a white spot, a chestnut spot or no spot were found. Therefore, the question arises whether there are three subspecies (L. s. cyanecula, L. s. svecica and L. s. azuricollis), or three forms of a single subspecies (L. s. azuricollis). The percentage of birds with and without a throat spot was similar in the four sampled areas, and the percentage of birds with a spot significantly increased with age. These observations suggest that some plumage characters, such as the throat spot, should not be used as taxonomic characters, at least in the area where this study was conducted.

The presence of wintering birds on manure and stubble was studied in the open farmland of eastern Poland. Among the 34 species recorded during transect surveys, 13 were on manure heaps and 16 in stubble fields. Species diversity did not differ significantly between these habitats but there were differences in the densities of individuals. Snow depth had a positive influence on the birds observed on manure heaps but had a negative impact on those associated with stubble. Logistic regression analysis showed that birds selected manure heaps with larger surface areas and larger areas of fresh manure, but that the duration of manure heaps did not affect their choices. This habitat can be used as an alternative food source and roosting site during long-lasting snow cover. This has been particularly important for the yellowhammer Emberiza citrinella, whose Polish breeding population is one of the largest in Europe.

Iberia is a very important wintering area for several species of European seed-eating passerines, including the reed runting Emberiza schoeniclus. The dynamics and structure of its wintering population remains unknown over large areas, especially in northern Iberia. This study aimed to test (1) whether northern Iberia is a stop-over region rather than a wintering area for non-breeding nominate race reed buntings; (2) whether sex and age ratios indicate a higher proportion of immature males and whether such ratios differ from those found in regions further south; (3) whether wing morphology varies at different stages of the non-breeding season, thus possibly revealing differential migration by different populations. Reed buntings were mist-netted weekly from October to April in a reedbed in the Ebro Valley, northern Iberia, between 2003 and 2009. The zone was used mainly by reed buntings stoppingover in this area during the autumn migration period but also, to a lesser extent, by an apparently stable population that overwintered in this zone. The high proportion of females supports the hypothesis that Iberia plays a major role as a destination area for female reed buntings during the non-breeding period. Seasonal variation in wing morphology suggests that populations of very distinct origin occur but the temporal patterns of their occurrence still remain unresolved. Our results suggest that longwinged reed buntings, which presumably have travelled from more distant regions, are more abundant in mid-winter.

Although interspecific competition for nests has been described in several raptor species, intraspecific interactions have rarely been reported. We describe three cases of intraspecific nest usurpation in the threatened bearded vulture Gypaetus barbatus in the Catalonian Pyrenees, where pairs were found nesting as close as 1.02 km apart. These observations could result from limited availability of suitable nesting habitat for this species, with birds being forced to compete for nest sites.

The screaming cowbird Molothrus rufoaxillaris is described as being sexually monochromatic, although it has a rufous axillary patch that shows inter-individual size variation. We investigated potential sex differences in patch size in 82 molecularly-sexed adults. All males exhibited large patches and 23 females had small patches; however, seven females lacked a patch and nine had large patches. Patch size was associated with sex and independent of body condition, location or date of sampling. We discuss several hypotheses that may explain the incidence of this male character in some females.

We investigated breeding densities and distribution of the woodpigeon Columba palumbus in woodland and urban habitats of Lithuania, Belarus and the Kaliningrad oblast (administrative district) of Russia. In Lithuania and Belarus, where the urbanisation process of the woodpigeon is in an initial phase, breeding densities in woodland habitats are higher than in urban areas. In the Kaliningrad oblast of Russia, where abundant urban populations have been established in towns for decades, breeding densities in urban habitats are significantly higher than in woodland sites. Available data indicate that at present the eastern border of the European distribution of well-established urban woodpigeon populations extends approximately along the western border of Lithuania, Belarus and Ukraine.

A project to reintroduce the Spanish imperial eagle in the province of Cadiz (Andalusia, Spain) began in 2002. The aim was to restore the former breeding nucleus, to encourage subpopulation interconnection and to ensure the long-term persistence of the southern metapopulation of this endemic Iberian species. A population reinforcement programme also began in 2005 at a location in the Doñana area (Andalusia, Spain) to improve the viability of this endangered subpopulation. Between 2002 and 2010, a total of 73 young Spanish imperial eagles were released at four locations by means of hacking. As a result, in 2010 a released male bred successfully with a non-reintroduced female and two young were reared. This was the first successful breeding event recorded in Cadiz province since 1960. An additional territorial pair also settled in the release area in 2010 and four more translocated individuals have made breeding attempts within nearby breeding subpopulations since 2006. The settlement and breeding of reintroduced individuals is the starting point of a future population and constitutes a relevant indicator for the evaluation of the project.

Egg size of the spur-winged lapwing Vanellus spinosus was studied in the Nile Delta, Egypt. Nests were located in three habitat types: on fish pond dykes, on dry fish pond bottoms, and in urban areas. Although clutch size did not differ between these habitat types, eggs from nests located on pond dykes were significantly smaller than those from nests located on pond bottoms and in urban areas. Differences in egg sizes between habitats may be related to food supply, parental quality or predation pressure.

Forum es una sección que pretende servir para la publicación de trabajos de temática, contenido o formato diferentes a los de los artículos y notas breves que se publican en Ardeola. Su principal objetivo es facilitar la discusión y la crítica constructiva sobre trabajos o temas de investigación publicados en Ardeola u otras revistas, así como estimular la presentación de ideas nuevas y revisiones sobre temas ornitológicos actuales.

The Forum section of Ardeola publishes papers whose main topic, contents and/or format differ from the normal articles and short notes published by the journal. Its main aim is to serve as a lighter channel for discussion and constructive criticism on papers or reseach lines published either in Ardeola or elsewhere, as well as to stimulate the publication of new ideas and short revisions on current ornithological topics.

Between 1990 and 2008 three independent estimates of national population sizes for common breeding birds have been produced in Spain. These estimates have been generated using three different methods: extrapolation of published information on bird densities; a rough assessment of population size using data collected by volunteers during breeding bird Atlas fieldwork; and density values obtained from a bird monitoring scheme based on point-count stations. In addition, an estimate of population size for common breeding birds has been produced in Catalonia, a Spanish autonomous community, using data from a bird monitoring programme based on line transects. The estimated relative abundance of bird species was similar for all these methods but absolute values differed up to 30-fold. The differences between the two more comprehensive datasets showed that the most recent national estimates were on average nearly five times as high as earlier ones, and more than ten times greater for 19% of species. The differences between estimates were especially notable for species associated with urban habitats. Although the estimates span a period of about 20 years, change in bird populations across time was not the main factor driving the observed discrepancies. Differences in sampling design and data analysis were probably responsible. Particularly important factors that account for these differences would be: (i) the absence of sampling design and the limited availability of data in earlier estimates; (ii) the more recent sampling of habitats, notably urban environments and farmland, which previously had not been well surveyed, thus increasing the population size estimates of species living there; (iii) biases resulting from the choice of sampling sites by observers, (iv) the use of different methods to estimate population density. To improve future population estimates it is suggested that additional work is needed to understand the shortcomings of bird monitoring programmes that are the data source for population size estimates of common birds. The results should also be disseminated in peer-reviewed journals. Ultimately, a refinement of the existing monitoring schemes or even the implementation of new approaches may be necessary to obtain reliable estimates of the population sizes of common birds.

Population estimates are an essential demographic parameter for assessing the threat status of species and the international significance of national populations. Murgui (2011) provides the most up-to-date review of the bird population estimates produced in Spain over past decades and he describes their methodological limitations, particularly those derived from data availability, sampling bias and analytical shortcomings. Two of the main procedures associated with the generation of reliable population estimates, the calculation of densities and their extrapolation over whole-species ranges are discussed here with the aim of contributing to improving comparability between estimates. In this connection, we present some new approaches developed in the Catalan Winter Bird Atlas 2006–2009, such as the stratification of density estimates using habitat suitability indices derived from species distribution modelling, and the consideration of detectability not only for common species but also for scarcer ones. Finally, applications of population estimates are discussed and we call for Europe-wide collaboration to enable between-country comparability of such estimates to be improved.

Estimating population sizes of birds is of fundamental importance in species-oriented conservation and management. Worryingly, discrepancies among different population estimates are widespread in ornithological literature. A complementary review to that carried out by Murgui (2011) on the available literature on national population sizes of Spanish birds is developed, putting the accent on data quality and methods used (geographical bias in sampling effort, sample sizes, census methods, detectability problems, consideration of the cryptic fraction of population not included in breeding pairs, how the number of breeding pairs is obtained, extrapolation methodologies, etc). I conclude with a positive, conciliatory, view about large-scale population estimates, where limitations of previous works enlighten future research and sampling programs.

The introduction of the great-tailed grackle Quiscalus mexicanus into the Valley of Mexico by Aztec Emperor Auitzotl during the years 1486–1502, is the earliest documented case of exotic bird introduction in the western hemisphere. This translocation was intensively managed and involved at least three different human interventions: (1) capture and transport of grackles to the Aztec capital, followed by release there, (2) supplemental feeding and (3) protection from human harassment and predation. Here I present new details of this ancient translocation gleaned from extant sixteenth-century manuscripts, and review what is known about each of the four stages of the introduction. The grackles were brought from more than one locality north of the Río de la Antigua (Gulf Coast region). After release at Tenochtitlan and Tlatelolco, they multiplied and dispersed. By 1577, they had spread more than 20 leagues, invading even areas between the Aztec capital and their native range. Complete protection of the introduced grackles ended relatively soon, either during the rule of Auitzotl or that of his successor Montezuma II (1502–1520). A related account of Aztec translocation of exotic plants can be used as a model to predict additional details of Auitzotl's introduction of the great-tailed grackle. Like the Auitzotl account, the plant account shows that a method and ideal of Royal Aztec translocation was to prevent the loss of each propagule. To achieve this goal, gardeners with experience cultivating the exotic plants in their native lands were imported from the Gulf Coast with them, and elaborate sacrificial rituals were performed. Large numbers of each exotic species were translocated, increasing propagule pressure and ensuring establishment.

The introduction of great-tailed grackles Quiscalus mexicanus by Aztecs in pre-Columbian times reported by Haemig (Ardeola, 58: 387–397) probably constitutes the most detailed information on an ancient exotic bird introduction. There is however sparse evidence, compiled here, showing that several domesticated and non-domesticated bird species were translocated even thousands of years ago by different civilizations, often ending on exotic introductions which last until current times. Given that different ancient cultures showed a great fascination for exotic birds and intensively traded them, we should expect a number of still unraveled old-time introductions worldwide. The combination of information from old-written documents, archeological and fossil findings, stable isotope analyses, art museums, and the most advanced molecular techniques should add exotic introduction surprises in the coming years.

The great-tailed grackle Quiscalus mexicanus was introduced by Aztec Emperor Auitzotl beyond its native range in 16^th century Mexico. Haemig (2011) provides valuable details on the transport, introduction, establishment, and spread of this species. However, here I argue that while this is an interesting account of a historical bird translocation, this is not the reason why this species has undergone one of the greatest range expansions of any native North American species during the 20^th century. Fossil records indicate that the species was already present in areas further north before this historical translocation. Moreover, it is a very plastic species and human commensal. Therefore, the northward expansion of this tropical species has been aided by anthropogenic habitat changes rather than a consequence of the active translocation by the Aztec Emperor Auitzotl.

Esta entrega incluye los resúmenes de algunas de las Tesis Doctorales defendidas en España en el curso 2010–2011 junto con otras no recogidas en reseñas anteriores. Se ha seguido una ordenación alfabética por Universidades y, dentro de ellas, por año y orden alfabético del autor.

The distribution pattern and abundance of species is the outcome of their ecology and of their evolutionary history, reflecting the influence of different ecological processes acting at different spatial scales. Large-scale distribution is mainly influenced by abiotic factors, fundamentally climatic ones, and this constitutes the species’ fundamental niche. On a smaller scale other factors such as resource availability, local climate or biotic interactions come into play, forming the realised niche, which is defined through thespecies’ habitat selection. This thesis is placed within this framework, applying conceptual and methodological advances of habitat selection and ecological niche theories and their effects on the study of population dynamics and distribution at different spatial scales of a steppe bird, the little bustard (Tetrax tetrax). Thus, the first chapter tackles the intermediate scales (landscape), showing that little bustard males included a larger than expected proportion of old and same-year fallows within their display sites relative to their availability. This indicates a significant preference for permanent and semi-permanent habitat types, which offer them both shelter and food. The selection pattern was constant between study years, indicating fidelity in habitat selection pattern. On the other hand, display sites were not spatially clumped. The relevance of food availability in the selection process was analysed in the next chapter, highlighting the existence of a higher abundance of large beetles within males’ territories than elsewhere in the surrounding landscape. Since large beetles constitute a relevant element of little bustard's diet during the breeding season, it can be concluded that males make a positive selection of areas holding valuable food resources to establish territories. The results of both previous chapters are discussed in terms of little bustard's mating system in the study population. The inclusion in the territories of areas with higher proportion of food resources or of particular habitat types that females could potentially use, could support the existence of real exploded or resource-based lek mating system (which is typical in other European populations). However, the fact that territories were not spatially aggregated suggests that, at least at the studied spatial scale, little bustards in this population may not form leks, for which clumped territories are an essential requirement. The fidelity in the selection of permanent and semi-permanent habitat types suggests that this preference may be related to some structural characteristics in the vegetation which are common to these substrates. This smaller scale (microhabitat) may allow measuring several parameters directly related to different ecological compromises. The results of the next chapter showed the existence of sexual segregation in microhabitat selection, which can be related to males and females’ different ecological constraints due to different life history traits. Thus, vegetation structure selected by females is determined by a compromise between the need for shelter and anti-predator surveillance. For its part, males’ selection was related mainly to the need of conspicuousness for courtship and territory defence. Accessibility to food resources seemed to be equally important for both sexes. Next chapter evaluates the influences of meteorological factors and land management on the oscillations and medium-term trends of two important little bustard populations. Both populations declined during 2001–2007, especially in Valdetorres (60%). Variation in habitat composition di

Report on rare birds in Spain 2009. This is the 26^th annual report of the Spanish rarities committee (Comité de Rarezas de SEO/BirdLife). This report includes 291 records on the presence of 84 rare bird taxa, with an acceptance rate of 75%. The report contains nine additions to the Spanish Bird List: Pacific Loon Gavia pacifica, white-backed vulture Gyps africanus, African purple swamphen Porphyrio porphyrio of the race madagascarensis, hudsonian whimbrel Numenius phaeopus of the race hudsonicus, bridled tern Onychoprion anaethetus, belted kingfisher Megaceryle alcyon, Naumann's thrush Turdus naumanni and black-and-white warbler Mniotilta varia. Having agreed acceptance criteria, the first accepted records of Caspian gull Larus cachinnans registered since 2005 are also included in this report. Second records for Spain of hooded merganser Mergus cucullatus, white wagtail Motacilla alba of the race subpersonata, house bunting Emberiza sahari and of a petrel assigned to the species pair Zino's/Fea's petrel Pterodroma madeiralfeae, are reported. Also accepted as second for the country is the record of a saker falcon Falco cherrug marked with a satellite transmitter in Hungary that crossed the Iberian Peninsula. Recorded for the third time are American coot Fulica americana, Ross's gull Rhodostethia rosea, booted warbler Hippolais caligata and Swinhoe's storm petrel Oceanodroma monorhis, which is also the first for the Canary Islands. Other new additions to the Canary Islands are least sandpiper Calidris minutilla and long-billed dowitcher Limnodromus scolopaceus. In 2009, a breeding pair of long-legged buzzard Buteo rufinus was confirmed for the first time ever, as well as red-billed tropicbird Phaethon aethereus in the Canary Islands for the third time and little swift Apus affinis in southern Spain for its tenth consecutive year too. The report also reflects an exceptional winter arrival of Iceland gull Larus glaucoides and glaucous gull Larus hyperboreus.

Esta nueva entrega contiene información sobre 185 especies repartidas por toda la geografía nacional. A las citas recibidas habitualmente se han incorporado algunas otras recogidas en distintos foros, así como algunos blogs y páginas web. Con el fin de facilitar la labor de recopilación de datos, se recomienda el envío de las observaciones de interés a la dirección noticiario@seo.org.