Antonio-Román Muñoz

Distribution of Bonelli's Eagle Aquila fasciata in southern Spain: scale may matter

Abstract Understanding factors that determine the distribution of the endangered Bonellis Eagle requires different approaches and analytical tools. These factors may differ depending on the spatial scale at which they act. Bonellis Eagle distribution in Spain has been studied previously using local and large (nation-wide) study area sizes, and human activities seemed not to affect negatively the occupancy of breeding territories. To study the factors affecting the species at an intermediate spatial scale we modelled Bonellis Eagle distribution in Málaga province (S Spain), where the breeding density is the highest known in Europe. We applied a favourability function based on generalized linear models using the presence/absence of breeding territories of the species, and the values of a set of variables related to climate, topography, interspecific competition with Golden Eagle Aquila chrysaetos and human activity. We obtained a parsimonious model that included cliff availability and distance to highways as predictors of Bonellis Eagle distribution. As highways may be seen as surrogates of intensive human activity, we conclude that, contrary to what was previously found at local or at nation-wide scales, human actions negatively affect the distribution of breeding territories at an intermediate scale. The construction of new roads and highways in the Mediterranean area of mainland Spain, which is the most climatically favourable region for the species, could have negative consequences for the Spanish metapopulation of Bonellis Eagle, particularly in peripheral populations or distant areas that depend on the arrival of immigrants to persist.

Invertebrates as Prey of Short-Toed Snake-Eagles (Circaetus gallicus)

INVERTEBRADOS COMO PRESAS DE CIRCAETUS GALLICUS Circaetus gallicus presenta típicamente una dieta especializada en reptiles. Sin embargo, el análisis del contenido estomacal durante el periodo de migración reveló la presencia de inverte, brados en la dieta de ejemplares jóvenes. La gran concentración de migrantes en la zona de estudio, el estrecho de Gibraltar, podría haber generado competencia por la presa principal, los reptiles, especialmente en el caso de los juveniles con poca experiencia. Nuestros resultados también podrían sugerir la explotación sistemática de un recurso trófico abundante, las escolopendras, coincidiendo con la finalización del verano.

Hybridisation between the Common Buzzard Buteo buteo buteo and the North African race of Long-legged Buzzard Buteo rufinus cirtensis in the Strait of Gibraltar: prelude or preclude to colonisation?

Natural hybridisation in Old World buzzards (Buteo) is an uncommon phenomenon with important ecological implications. This genus constitutes an intricate radiation of genetically poorly differentiated raptors whose taxonomic classification is a frequent subject of debate. We report the first case of successful hybridisation between the African subspecies of the Long-legged Buzzard Buteo rufinus cirtensis and Common Buzzard Buteo buteo buteo in a new contact zone in the Strait of Gibraltar (southern Spain). The hybrid offspring showed mixed characters from parental species indicating that, among others, hybridisation could explain the increasing presence of phenotypically odd reddish buzzards in southern Spain and northern Morocco. Given their close phylogenetic relation and their recently reduced allopatry, an increase in the hybridisation rate, fertile descendants and genetic introgression seem to be viable. We identify the potential contact zones where genetic monitoring is needed to gain insight on the real extent of this hybridisation and its possible effects on the current climate change scenario.

Assessment of offshore wind farm effects on birds and needs to plan their future development in Spain

Summary.— Wind farms have a negative impact on several animal populations, with birds and bats assumed to be among the most heavily affected taxa. In addition to the extensive development of wind power on land, currently several European countries have offshore wind farms (OWFs) in operation, as well as proposals to build many more. Considering that seabirds spend more than 90% of their life at sea, it is clear that they may interact with these man-made structures. To date, information on how to measure the impact of OWFs on seabirds is very scarce. In many cases it comes from non-peer reviewed reports made for specific assessment studies, very often carried out without appropriate standard methodologies, that raise questions regarding the level of confidence that they merit. In this paper, we describe the current political framework concerning the possible development of OWFs in Spain. Based on this, we comment on both the relevant variables necessary to assess the impacts of OWFs on birds and the methodologies available to collect those variables in the field, discussing the strengths and weaknesses of each method. We show the importance of collision risk models, vulnerability indexes, cumulative impact assessment and population viability analysis as management tools. Mitigation measures that have the potential to minimise impacts are also summarised. We conclude with a discussion of the different steps to follow to attain a ‘clean’ development of offshore wind energy in Spain.

Is the Eurasian Reed Warbler Acrocephalus scirpaceus a Regular Wintering Species in the Iberian Peninsula? Ringing Data Say Yes

Abstract. Recent climate change is frequently invoked as the cause of changes in phenology and distances of migration. Birds are expected to reduce the length of migration in response to milder climatic conditions, and during the last years, there are a growing number of records of European long-distance migrants wintering in the Iberian Peninsula. For this reason, we have used in this study the available ringing and recoveries data for the Eurasian Reed Warbler in the Iberian Peninsula during winter, spanning 1959–2015. We show that during the last decades this insectivorous species occurs regularly during winter in South-western Europe, which could be related to the recent climate change. Some Iberian birds wintered in breeding areas, or nearby, which could indicate a potential process of sedentarization, while Eurasian Reed Warblers from Central and Northern Europe shortened the migration distance avoiding the crossing to Africa. Iberian wintering grounds seemed to be related to the origin of the birds, with British Eurasian Reed Warblers staying more northerly that individuals from Central Europe, and Eastern birds showing a tendency to winter on the Mediterranean coast. Our results support the contemporary trend of migrants overwintering at higher latitudes. Despite the considerable increase of wintering records during the last decades, we cannot confirm a real expansion because there has been an increase in ringing activity over the study period. Nevertheless, the presence of this species has become consistent during winter in well-sampled areas where it was absent in the past. With warmer winters we expect changes in the migratory system, and also an increase in frequency of long-distance migrants that avoid the crossing of the Mediterranean and the Sahara desert to remain in southern Europe during cold months.

Individual Variation in the Over-Summering Areas of Immature Short-Toed Snake Eagles Circaetus gallicus

Abstract Satellite tracking is an invaluable tool in the study of bird movements. However, the normally small sample size it involves makes it difficult to obtain data spanning the entire range of migratory behaviour found in particular populations. We recently reported that Spanish immature Short-toed Snake Eagles leave their winter quarters in sub-Saharan Africa to occupy summering areas in northern Africa (north of the Sahara), in contrast to previously reported behaviour of a young French eagle which remained during the summer in the sub-Saharan wintering range. A more recent increase in the sample size of tracked young snake eagles further extends our knowledge of the summering behaviour of this species with one immature reaching the European range but occupying four widely-separated areas during the course of the summer. In the short-term, technology progress may provide the normal use of representative samples to increase accuracy in movement ecology studies.