Population estimates for the diverse raptor assemblage of Dadia National Park, Greece.

Dadia National Park, which is situated in north-eastern Greece, close to the border with Bulgaria and Turkey, is characterised by one of the most diverse arrays of breeding raptorial species in Europe. The first raptor survey was undertaken in the 1970s, but until 1999 most surveys were circumstantial and nonsystematic. Considering some of these species are globally endangered and included in Annex 1 of the Birds Directive, and that raptors in general are considered key indicators of biodiversity and ecosystem health, a systematic raptor monitoring programme was established by WWF Greece in 2000. This paper presents the results of this programme including the population status, trends and breeding densities of raptors from 2001 to 2005. Some 18–19 species bred in the area regularly, at densities ranging from one pair per 100 km² (e.g. long-legged buzzard Buteo rufïnus and peregrine falcon Falco peregrinus) to 30 pairs per 100 km² (common buzzard Buteo buteo). The total number of raptor territories was stable with an average of 321 ± 15.5 territories (77 territories/100 km²) with no overall trend and little fluctuation. Although the population size has increased for several species since the mid 1990s, data from the first surveys in the 1970s suggest that some species are still recovering from the decline suffered in the 1980s. The populations of six species have remained stable since the 1970s, whilst five species, including the Egyptian vulture Neophron percnopterus, have shown a gradual decline. The black vulture Aegypius monachus was the only species with a confirmed increase, a further three species showing a probable increase. The long-term trend for four species, including the common buzzard, is unknown due to insufficient data from the 1970s.

Breeding phenology of blue tits in Mediterranean stone pine plantations: effects of nestboxes and holm oaks.

A blue tit Cyanistes caeruleus population nesting in a Mediterranean stone pine plantation Pinus pinea in the Sierra Morena, Spain, was studied during 2007–2009. Nestboxes were distributed 50 m apart in a grid and territory size, territory location, number of Iberian holm oaks Quercus ilex in territories and number of conspecific neighbours were determined. Laying date, clutch size, hatching success, fledging success and fledgling mass were also recorded. Linear transects were carried out both within and outside the area where nestboxes were located. Over 50% of nestboxes remained unoccupied. The number of conspecific neighbours was positively associated with territory size. Occupied nestboxes had more holm oaks in their vicinity than did unoccupied nestboxes. Breeding success and fledgling mass were similar across territories although laying was earlier in larger territories and in those rich in holmoaks. Clutch size declined with laying date. Blue tits nesting in stone pine plantations are limited in their breeding phenology by the availability of holm oaks in the vicinity of the nest and by territory size. Holm oaks and territory size are more important for attainment of breeding condition by females than for raising nestlings.

Temporal changes in diet and prey selection in the threatened Olrog's gull Larus atlanticus breeding in southern Buenos Aires, Argentina.

We examined temporal changes in diet composition and prey selection in the threatened Olrog's gull Larus atlanticus breeding at Bahía San Blas, Argentina. Diet was assessed through pellet analysis (N = 360) and chick stomach samples (N = 120) during 2006 and 2007. Prey availability was sampled in 2,084 1m² quadrats distributed throughout Olrog's gull potential feeding areas. Gulls fed almost exclusively on three crabs: Neohelice granulata, Cyrtograpsus altimanus and Cyrtograpsus angulatus. Diet composition was similar between years. The relative importance (%IRI) of different crab species, assessed through pellet analysis, varied across the breeding cycle. During incubation, N. granulata predominated (> 90%) while C. altimanus comprised less than 2% of the crabs taken. This relative contribution was reversed during the young chick stage (< 10% v. > 60%, respectively) and was 40–50% for both species during the old chick stage. Stomach sample analysis provided a similar pattern of %IRI values for the chick stages. Sizes of available crabs differed significantly between species, C. angulatus and N. granulata both being similar-sized but larger than C. altimanus. Gulls selected N. granulata during incubation and largely C. altimanus during the chick stages. Our study suggests that Olrog's gull depends on three crab species, confirming its specialised feeding ecology during the breeding season. Their relative consumption, however, can change temporally, probably in response to restrictions imposed by the different requirements of adults and chicks.

Flocking behaviour does not favour high chewing lice load in shorebirds.

As shorebirds show a high variability in the flocking behaviour among species from solitary ones to species forming flocks of hundreds of individuals, they offer a good opportunity to test if the proximity of individuals in highly gregarious species increases the risk of horizontal ectoparasite transmission in comparison with solitary species. We investigate whether there exists a higher ectoparasite load in gregarious shorebirds compared to solitary ones at Salinas del Cabo de Gata, Almeria, Spain. Seven species of shorebirds (Scolopacidae and Charadriidae) were captured with mist-nets during the night. Ectoparasites were estimated by means of visual examination of seven body regions and differentiated in five levels of infestation. Flock size was divided into three categories: solitary species, species forming flocks up to 99 individuals and species forming flocks of more than one hundred. Based on the application of a phylogenetic comparative method, our results show that the abundance of chewing lice is not related with flocking behaviour.

Conservation opportunities in Spanish juniper Juniperus thurifera woodlands: the case of migratory thrushes Turdus spp.

Spanish juniper Juniperus thurifera woodlands are the core habitat of several sites included in the Nature 2000 Network and the wintering ground of many European thrushes Turdus spp. These birds have a major ecological role as seed dispersers and are increasingly taken into account in the design of strategies aimed to conserve or restore plant communities. Socio-economic changes in rural Spain have reduced traditional sheep grazing in juniper woodlands, which are now increasingly used for wood production. This has brought the opportunity to improve their carrying capacity for migratory thrushes. Here we explore the spatio-temporal patterning of fleshy cone production and the way birds track this resource. We also investigate whether fleshy cone availability constrains bird numbers. The results show sharp losses of cones during the ripening period, inter-site and inter-winter changes in cone production and the tracking of ripe cones by birds. Mean availability of ripe cones in poorly productive patches was insufficient to maintain thrushes in mid January and highly productive patches offered resources to maintain birds for around 12 days. This suggests an insufficiency of food in the woodlands to permit thrushes to complete the winter and to begin their return northward migration in March. These results are used to suggest some guidelines for improving the carrying capacity of these woodlands for migratory thrushes.

Do blackcaps Sylvia atricapilla stopping over at a locality from Southern Iberia refuel for crossing the Sahara?

Migrants that cross large inhospitable areas must accumulate large loads of fuel to reach their destinations successfully. The stopover strategies of European long-distance migrants are relatively well studied for species that overwinter in tropical Africa, but less so for those that overwinter mainly around the Mediterranean and of which only a fraction reach tropical Africa. Our aim here was to analyse whether blackcaps Sylvia atricapilla stopping over in southern Iberia gain sufficient fuel in this region to be able to reach tropical Africa. Blackcaps were mistnetted during the autumn migration period of 2005 at a locality in Northern Iberia (Loza) and another in Southern Iberia (Doñna). Blackcaps at Doñana had lower fuel loads and a slower fuel deposition rate than at Loza, and the estimated flight ranges from both sites were insufficient to reach tropical Africa. The stopover duration was similar at both localities. If trans-Saharan birds occurred at Doñana, they would need to refuel at other stopover sites in Southern Iberia or in Northern Africa before crossing the Sahara. The circum-Mediterranean region may hence be of great importance for the fraction of the blackcap population that overwinters in tropical Africa.

Factores determining the large-scale seasonal abundance of the common kestrel in Central Spain.

Details of landscape variables that determine the large-scale distribution of the common kestrel in Central Spain are provided. The most influential variables largely differ between breeding and wintering seasons, although purely geographical variables decide the overall trend in the species' distribution: the kestrel is more common in northwestern, moderately hilly locations below 900–1,000 m a.s.l. of the study area. Despite its association with farmland, agricultural use variables do not determine the year-round distribution of the kestrel. Moreover, breeding abundance is negatively correlated with farmland. These results exemplify the need to compare seasonal patterns of abundance/distribution in order to be able to state the habitat requirements of a species with precision.

Winter habitat influences the number of feather mites of two species living on European robins Erithacus rubecula.

Plumicolous feather mites are a little-known but diverse and abundant group of symbionts of birds. The nature of the feather mite versus bird relationship is controversial, with reports ranging from suggestions of parasitism to evidence supporting commensalism or even mutualism. In addition, little is known as to why enormous inter-individual variation in mite loads is observed within bird species. In this study we show that migrant European robins Erithacus rubecula differ in their load of Proctophyllodes rubeculinus and Trouessartia c.f. rubecula by a factor of 2 to 3 depending on the winter habitat that they occupy. Such variation cannot be explained as being due to robins from different geographic origins wintering in different habitats, as wing shape and stable hydrogen isotope ratios (inferring breeding origin) in feathers of those robins did not explain variation in mite loads. Furthermore, there were no age or sex effects on the number of mites, but abundance increased as winter progressed. Robins wintering in the best putative habitat had higher mite numbers and the fact that there was no correlation between mite infestation levels and either muscle or fat scores indicates minimal costs to the host and hints at a commensal or mutualistic relationship. More research is needed to better understand the factors underlying differences between habitats. Meanwhile, habitat must be taken into consideration in future studies of the relationships between feather mites and birds.

Nest site preference and nest success in blackcaps Sylvia atricapilla in Poland.

Predation is reported to be the main cause of nest failure in songbirds and selection of safer nest sites is thus an important determinant of breeding success. We studied the effect of nest site location: in bramble, elder or hornbeam, on breeding success as well as selection of different nest sites in the blackcap Sylvia atricapilla, a species whose nests are heavily preyed upon both by rodents and corvids. We found that breeding success differs between nest site types, with higher levels of predation of nests built in elder or hornbeam than of those in bramble. We also found that blackcaps select bramble when it is available within the nesting territory. Nests in bramble were better concealed than those in elder or hornbeam. Since nest height above the ground did not differ according to the plant species used, nest concealment was probably the main factor affecting blackcap nest survival.

Nest characteristics and breeding performance in great tits Parus major.

For birds, building a nest entails a number of costs but it confers important benefits, so that nest quality is often positively associated with reproductive performance. Our main objective was to study the relationships between nest characteristics and breeding performance, and the possible between-year variability in these relationships. We used great tits Parus major as the model species and studied a population breeding in nestboxes within orange plantations in eastern Spain. The study only considered first clutches, in two consecutive years. Nests were visited as frequently as necessary to record basic breeding parameters. We measured and weighed all nests during the incubation period, took biometric characteristics of parents and nestlings (tarsus length, weight and condition, and parental wing length) and measured the immune response of chicks (phytohemagglutinin test). We used principal component analysis to reduce the number of nest variables to three relevant components. Overall, 2007 seemed to have been a more favourable year, with larger clutch sizes and heavier fledglings produced than in 2006. Laying date was earlier in nests with larger nest cup diameter, hatching success was higher as relative cup depth increased in 2007, and fledging success increased as overall nest size increased in 2007. The only significant relationship between parental traits and nest characteristics was that first year females built deeper nests than older ones. Females with longer tarsi and in poorer physical condition started laying earlier. Increased fledging success was associated with decreasing male tarsus length and fledgling condition was better in nests attended by older males. In general, nest characteristics were positively related to breeding success, although specific relationships between the different components could vary between years. These relationships have been more evident in a trophically “good” year than in a “bad” one.

An appraisal of the status and distribution of waterbirds of Algeria: indicators of global changes?

North Africa is generally thought to play a key role for wintering and staging migrant birds. This study presents a detailed assessment of the status of waterbirds of Algeria with an emphasis on changes in species composition and distribution of breeding wetland and marine birds. A total of 97 species of waterbirds were identified with 41 species breeding. Marked environmental changes in North Africa over the past two hundred years that are relevant to waterbirds have included wetland drainage, persecution, introduction of exotic fish, increases in open-air refuse dumps and climate change. These changes have affected waterbirds differentially with some species increasing in numbers and expanding their range and others teetering on the verge of local extinction. When examining changes in the present breeding avifauna since the nineteenth century or the mid-twentieth century, the guild renewal rates were 18.3% (with a net loss of 5 species) and 4.8% (with a net gain of 3 species), respectively. Data suggest that many Mediterranean waterbird populations are structured as metapopulations, prompting the need for international cooperation to study population dynamics on a wider scale and to devise conservation strategies that take into account the interconnectivity of wetlands on a regional level.

Bonelli's eagle Aquila fasciata is in decline across the entire circum-mediterranean region, partly on account of habitat loss. Knowledge of territory characteristics is essential to developing effective conservation plans.We report on the extent and variability of territory size, and on the principal areas used, following radio monitoring of three adult males in Extremadura, noting individual and temporal differences.

The occupancy of 35 irrigation ponds by the black-winged stilt Himantopus himantopus in southeastern Spain was analysed. The frequency of pond use was noted during 2002–2008 and settlement order and breeding abundance were monitored in 2008. Eight pond attributes were assessed for each pond and related to pond use during the breeding season. Some ponds were used more than others, those that had been most used previously being occupied first and by the greatest numbers in 2008. Pond design was the most explicative variable, alongside size and presence of vegetation.

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