The urbanization process contributes to a general impoverishment of biodiversity, yet the underlying reasons remain poorly understood. The classical explanation is that organisms differ in tolerance to urbanization, but current supporting evidence is insufficient because of the difficulties of quantifying such tolerance accurately in comparative studies. However, with information on the abundance of species along urbanization gradients, it is possible to construct simple urbanization tolerance indices that account for the fact that the density of a species in an urbanised environment depends in part on its density in the surrounding natural environments. The use of such metrics is likely to change our perception of how animals respond to the urbanization process, allowing a better investigation of whether urban communities are non-random assemblages of species and, if so, whether such non-random patterns are caused by adaptations that make some species more tolerant to urbanization than others.

Because of the urgency engendered by climate change and habitat loss, biodiversity must often be assessed indirectly, through the use of indicators. Recent studies have provided evidence of the usefulness of raptor species as indicators of high species richness. However, other studies have shown that presence of similar species of predators does not always indicate areas of high diversity. We used atlases of vertebrate data in Andalusia (southern Spain) as different indicator sets to select networks of priority areas based on complementary species rarity. We tested the value of each indicator group as a surrogate for the conservation of all other target groups. We found that a reserve based on raptors is the best option in terms of all other species representation. Raptors performed well in the representation of other birds, amphibians, reptiles and, to a lesser extent, mammals. Complementary sites based on raptor species also show higher plant community diversity than other sites. Based on 395 different European monitoring schemes and Zoological Record databases we suggest raptors may be an easy and cost-effective group to monitor biodiversity compared with other vertebrate groups. Finally, our results point out that farmland landscapes are under-represented in the existing protected network in Andalusia. According to the present study, we suggest raptors may guide farmland habitat acquisition in order to better preserve terrestrial vertebrate species within the existing protected network in Andalusia.

We assessed the potential overlap in diet composition of the kelp gull Larus dominicanus and the threatened Olrog's gull L. atlanticus breeding syntopically at Bahía San Blas, Argentina, during two breeding seasons (2006 and 2007). Diet was studied using regurgitated pellets (180 per species and year) and chick stomach samples obtained through the water offloading technique (60 per species only in 2007). Kelp gulls fed on at least 18 prey types. Fish was the most important diet component (73.3–85%, depending on breeding stage and year), mainly stripped weakfish Cynoscion guatucupa (63.3–75%). Crustaceans were the main prey encountered in Olrog's gull diet, particularly the crabs Neohelice granulata and Cyrtograpsus altimanus, with frequencies of occurrence of over 98% at all breeding stages. Fish in Olrog's gulls diet were only recorded in the old chick stage and in less than 3.3% of samples, while the occurrence of crustaceans in kelp gull diet throughout the study period was never greater than 13%. The specialised crab-based diet of Olrog's gulls contrasts sharply with the generalist and opportunistic diet of the kelp gull. The characteristics of prey remains and the large size of stripped weakfish found in kelp gull diet samples suggest they were obtained from coastal sport and artisanal fisheries. Future studies should monitor the consumption of fish waste by kelp gulls as a function of changes in fishing effort, and assess the dietary overlap between both gull species in coastal sectors where breeding birds have no access to this human-derived food source.

Moult is one of the most energy-demanding events in the annual cycle of a migratory bird. As a consequence, moult patterns have evolved that separate moult from other costly life-cycle stages and that exclude unnecessary replacement of the feathers. We studied two Spanish blackcap Sylvia atricapilla populations with the aim of elucidating variation and flexibility of their postjuvenile moult pattern. In contrast to most juveniles of this species, which normally undergo a partial moult both in captivity and in the wild, we found complete moult in 2 juvenile blackcaps. Complete moult was also inferred for another 7 birds, which were in active moult. Eight of these birds were trapped at a site in northern Spain and one originated from a partially migratory population from eastern Spain. This bird, held under the same environmental conditions as other 31 juveniles from the same population, moulted all primaries in captivity while the other 31 juveniles invariably undertook a normal partial post-juvenile moult. Therefore, it seems likely that complete post-juvenile moult observed in this bird was not induced by environmental conditions but had a genetic basis. Thus, we show that previously undetected variation among post-juvenile moult patterns is present in wild blackcaps and suggest that variation in the expression of important life-history traits could represent a potential reservoir for adaptive changes. This finding is in line with the great adaptive capacity of blackcap, repeatedly observed both in wild and in captivity.

Factors determining departure decisions of migrants from a stopover site can be extrinsic and/or intrinsic but the relative role of each of these factors on departure decisions is still poorly known. Date and wind should be the main factors determining departure decisions in a long-distance migrant, which is expected to minimise duration of migration. Date was considered as an intrinsic factor and wind as an extrinsic one. We analysed the capture-recapture data of a long-distance migrant European songbird, the sedge warbler Acrocephalus schoenobaenus, from a stopover site in northern Iberia during the autumn migration period to quantify the relative importance of several factors on emigration likelihood. Cormack-Jolly-Seber (CJS) models were used to estimate the emigration likelihood. From 107 models tested, only the model with an additive effect of date, tailwind assistance and population size substantially supported the data. As expected, sedge warblers were more likely to depart with high tailwind values and late in the season and, contrary to expectations, with decreasing sedge warbler abundance.

Within-season changes in habitat and distribution of breeding birds have been poorly investigated but are likely to be important for several species. With this work, we investigated what factors affect the density of a multi-brooded bird species breeding in apple orchards, the song thrush Turdus philomelos, in three different periods of the breeding season in the Trento province, northern Italy. Birds were counted along transects, and analyses carried out using a Generalised Mixed Linear Model (GLMM) approach. A further analysis assessed the effect of conspecific occurrence and habitat variables on the changes in local density. Thrush density changed during the season, increasing from early to late period, and was mainly affected by tree height (positively), bare soil (negatively in third period), shrubland (negatively), wetland (positively), grassland (negatively), percentage of rows irrigated by droplet system (negatively), percentage of orchard covered by anti-hail nets (negatively), urbanised area (negatively in first period, positively in third period). Intra-seasonal variation in density was affected by tree height (positively), anti-hail nets (negatively), use of herbicide during the late period (negatively), difference in bare ground (negatively), and initial thrush density (negatively), the latter suggesting that best habitats are occupied first. Multi-brooded bird species may show varying density and changing species-habitat relationships during the breeding season, and their distribution could change during the period of reproduction. This pattern could apply to a large number of bird species, requires deeper investigation and could have important implications for conservation and management.

We describe the use of different agricultural habitat types by little bustard females nesting and rearing young chicks, based on observations gathered over a five-year period (2001–2005) in central Spain. The frequency of occurrence of nest or family locations within male lekking territories is also evaluated, as well as their association to habitat types preferred by females for nesting or chick rearing. A total of 28 nesting or brood locations (19 nests plus 9 families) were recorded over the study period. Habitat use did not differ significantly between nesting females and families. Both for the total sample (nests plus families) and the only-nests sample, the frequency of recorded locations differed between agricultural habitat types, with long-term fallows (older than two years) being the most frequently used. Young fallows (1–2 years old) were significantly more frequently used than cultivated habitats and ploughed-fields together, but less than long-term fallows in both samples. Nest plus family locations were more frequently found within estimated male territories than outside. Both in the total and the only-nests samples, locations within territories were found only in long-term and young fallows, the former being the most frequently used habitat type. These results from a mosaic cereal landscape provide further support to the role of long-term fallows as a critical habitat for breeding female little bustards found in other, more extensive, study areas, and reinforce the role of young fallows as an alternative breeding habitat when the former are absent or unsuitable. The strong dependence of breeding little bustards on fallows highlights the need to maintain their vegetation structure suitable as nesting and chick rearing habitats in order to prevent the species' current population decline in Spain.

The Pantanal region (Brazil) is under increasing anthropic pressure partly due to an increase in tourism and there is a lack of information about the influence of human presence on avifauna. Here we study the relationships between human activity in the river (boats and fishermen) and 15 bird species along a 70 km stretch of the Paraguay River, also including other confounding factors such as distance to towns and spatial autocorrelation. Human density along the river was low and as expected decreased with distance from towns. Bird richness and density were negatively associated with human density and the distance to towns along the river, suggesting a permanent impact on avifauna. Riparian forests had higher bird density. Four species were apparently sensitive to human presence: the anhinga Anhinga anhinga, the great white egret Egretta alba, the ringed kingfisher Megaceryle torquata and the southern screamer Chauna torquata. Thus, these species could serve as indicators of human pressure. Any management plan for sustainable development of the study area should preserve the riparian forest, consider the control of numbers of tourists and people in the river, and monitor the bird community, especially the sensitive species.

The Azores archipelago is located in the North Atlantic, consequently observations of birds of both Palearctic and Nearctic origin are not rare there. We evaluate the local occurrence of two allopatric snipe, the common snipe Gallinago gallinago and Wilson's snipe G. delicata. A hurdle model for fortnightly snipe counts on Säo Miguel Island suggests an arrival of foreign birds in October-November. Morphological characteristics were used to identify both snipe species among birds shot during hunting seasons on Pico and São Miguel Islands. The Nearctic Wilson's snipe is an annual winter visitor to the archipelago, representing from 8% of the hunting bags on Pico up to 56% on São Miguel. Further studies, using emerging technologies, may shed light on the origin of the migratory birds and their interaction with the local common snipe breeders.

Several boreal taxa can be found in southern latitudes in fragments of high altitude alpine habitat. Some of these taxa have remained isolated from the main populations in northern latitudes as a result of the distribution changes during the last glaciations, being known as glacial relict populations. Such relict populations have often differentiated from the main population as a result of isolation and genetic drift. The Tengmalm's owl Aegolius funereus is a widespread boreal forest species distributed throughout boreal Eurasia and North America. The westernmost Eurasian breeding population is located in the Pyrenees Mountains, and was discovered less than 50 years ago. We studied the genetic structure of this Pyrenean population of Tengmalm's owl, and compared it with a northern latitude population from Fennoscandia. Despite being isolated by several hundred kilometres from the closest breeding grounds, we found no differences in the genetic structure of the mitochondrial DNA when compared with the central population. Our results suggest that this population has been recently, or still is connected with the main population.

We explored the post-breeding home range and autumnal migratory movements of a sample of the Iberian black stork Ciconia nigra population. A total of 10 black storks, consisting of 8 nestlings, 1 immature and 1 adult from Portugal (N = 5) and Spain (N = 5) were equipped with satellite transmitters and tracked during the post-breeding period until the autumnal routes were complete. We estimated adaptive kernels to define the size and structure of the home ranges before migrating via the Strait of Gibraltar. Three storks died in Iberia before crossing the Strait of Gibraltar (one immediately after leaving the nest and two during movements across Spain before crossing the Strait of Gibraltar) and the rest moved to winter in Africa. Before crossing the Strait, the total distance travelled during the postbreeding period varied considerably among individuals, ranging from 100 km to more than 800 km. Mean movements per day ranged from 1.5 to 26.1 km. The tagged Iberian black storks began autumn migration between mid-September and beginning-October. Most storks flew to the Sahel without stopovers in 2–3 weeks. The mean autumnal migratory distance of all Iberian storks together was ± SE, 3,673.5 ±516 km, and the migration speed was 208.6 ± 21. We came to the conclusion that the tagged Iberian black storks show large-scale migration routes similar to other European populations.

We present the results of a breeding census of Dupont's Lark carried out in the Autonomous Community of Valencia in 2011 using the mapping method and an analysis of the recent trend for this population. The population was estimated at 44–47 males, located in five habitat patches of the Rincón de Ademuz, in zones where the species had been detected previously. Density in these patches fits within values expected according to the relation between patch size and density found in the populations of the nearby provinces. Comparison to previous studies reveals that population of Valencia has suffered an annual decline rate of around 10% on average, thus the implementation of a conservation plan is required to ensure the survival of the species in the study area.

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