Human-induced habitat changes have been typically linked to negative effects on native species, but an increasing number of studies show that many species are unaffected by these changes or even benefited from them. The Burrowing Owl Athene cunicularia is a raptor species that has deserved special attention in recent years due to its capacity to live in a variety of natural and modified habitats. In this study, we analyzed habitat characteristics that determine the habitat selection of the Burrowing Owl at the nest-patch, territory and landscape scales in the Pampas of Argentina. We performed broadcasting call surveys to evaluate presence-absence of owls at random points. In addition, we measured habitat variables in the field and used satellite imagery to obtain land-use information. We used Generalized Linear Models to explore the influence of habitat variables on the probability of occupancy by Burrowing Owls. Our results indicate that Burrowing Owls demonstrate good ability to live in a wide variety of habitat types and with different disturbance levels in the Pampas. At the nest-patch scale, which includes the nest-site and the surrounding patch around it, the presence of owls was positively associated with the horizontal visibility and was influenced by the land-cover type. At the territory scale, the occurrence of owls was positively associated with the presence of active (non-vegetated) dunes and negatively with croplands. At the landscape scale, the presence of owls was negatively associated with the disturbance level and positively with the amount of borders between habitats. A unique multi-scale model containing variables of the three spatial scales was more robust to explain variation in Burrowing Owl occupancy patterns than any single-scale model. This would reveal the hierarchical nature of habitat selection by Burrowing Owls in the Pampas, comparable to that observed in North American populations.

Mute Swan Cygnus olor numbers have recently increased in a dramatic fashion in Western Europe and in North America, suggesting there could be potential consequences for the rest of the waterbird community. Breeding Mute Swan pairs may behave territorially towards other waterbirds, taking advantage of their larger size, and hence cause concern regarding their potential effects on waterbird communities. We studied how the within-site distributions of breeding Mute Swans and other waterbirds were related to each other, in order to assess if there is support to the assertion that breeding Mute Swans may affect the distribution of the other waterfowl within waterbodies. We mapped waterbird and swan distribution within fishponds during the Mute Swan breeding period. Relying on spatial point pattern analysis, our first finding is that breeding Mute Swans were located in the vicinity of the other waterbirds, using the same area within fishpond. Waterbirds do not completely desert the area used by breeding swan pairs within a waterbody, hence not supporting the claim that Mute Swans dislodge the other species. If an exclusion process by Mute Swan breeding pairs towards waterbirds exists, it is not strong enough to generate deserted areas by waterbirds around breeding Mute Swans. Our second finding is that breeding Mute Swans were not located where the density probability function for waterbird presence was the greatest within a fishpond, i.e. breeding Mute Swans were not located in the centre of groups formed by other waterbirds within each fishponds. This may indicate slightly different micro-habitat preferences or use within fishponds, or could indicate the potential occurrence of interactions. In conclusion, these results question whether the increasing Mute Swan populations actually directly threaten the other waterbird communities in such habitats, and require population control as is often claimed.

In the present study, we used 37-year long dataset on Tawny Owls from the annual monitoring of nestboxes at a sample plot in Central Lithuania. We expected that Tawny Owls responded to changes in land use practices, stemming from a change in both political and economic system, which may affect prey abundance and composition, breeding performance and demography. To analyze temporal changes in monitored parameters, we divided the study period into three phases (1978–1989, 1990–2001 and 2002–2014), corresponding to different socio-economic conditions. The number of nesting pairs of Tawny Owls decreased significantly in the last 13 years of the study, but the number of successful pairs fluctuated without any trend. The clutch size and number of nestlings varied without significant trends, but nesting success improved over the last 13 years. Annual apparent survival probability of the female Tawny Owls did not vary significantly over the study period (model averaged values between 0.71 and 0.73). Owls occupied nestboxes irrespective to the distance from the agricultural land during the first two study periods, but since early 2000s, owls tended to occupy nestboxes located deeper in the forest. Birds and small mammals were similarly important as prey items by biomass. Since the 1990s, the share of Microtus voles significantly decreased in the diet, while that of birds increased. In summary, changes in the diet, improved nesting success of the Tawny Owl and tendency of nesting in forest interior may indicate ongoing complex responses to the changes in environmental conditions.

Generalist brood parasites, like Common Cuckoos Cuculus canorus, target many host species. Why other sympatric hosts are not used, or actively avoided, remains one of the main gaps in our understanding of parasite-host coevolution. Cavity nesting passerines always represented a text-book example of unsuitable hosts but recent evidence casts multiple doubts on this traditional view. In general, any species can become an unsuitable host for a parasite at laying, incubation, or nestling stages with the last one being much less studied than the others. Therefore we examined Cuckoo chick performance in five cavity nesting host species, including one regular Cuckoo host — the Common Redstart Phoenicurus phoenicurus and four non-hosts: the Pied Flycatcher Ficedula hypoleuca, Spotted Flycatcher Muscicapa striata, Great Tit Parus major, and Coal Tit Periparus ater. Natural nests of non-hosts, as opposed to artificial nest boxes with small entrance holes, are often placed in cavities that show both entrance and inner cavity sizes large enough for female Cuckoos to lay and Cuckoo chicks to fledge. We did not find any evidence for chick discrimination in non-hosts, i.e., no chicks were rejected, attacked, or neglected. Cuckoo chicks grew similarly in nests of all four species of non-hosts, similarly to chicks in host Redstart nests, and generally better than in nests of the most numerous Cuckoo host, the Reed Warbler Acrocephalus scirpaceus. Although Cuckoo chick fledging mass was highly host speciesspecific (i.e., showed high statistical repeatability across various host species), we did not find any evidence for the hypothesis that host body size (mass) positively affects parasite chick growth (fledging mass or age). These findings provide impetus to further study apparently unsuitable hosts and perhaps even reconsider traditional classifications of host suitability in the context of brood parasite-host coevolution.

Studies dealing with the individual survival of birds in open populations usually estimate survival according to capture-recapture models like the Cormack-Jolly-Seber (CJS). In fact, these models estimate local apparent survival (ϕ), which is a combination of the probabilities of true survival (S) and site-fidelity (F), i.e. death and emigration are confounded. These S and F parameters can be estimated by using ‘robust’ models (e.g. Barker's model), which use additional resighting and dead reports data. We aim to compare the results (and associated biological implications) obtained by analysing juvenile and adult survival in a Polish urban population of Blackbirds Turdus merula using both the CJS and Barker models. Our CJS models estimated high ϕ values for both juvenile and adult birds (0.48 and 0.62, respectively). The lower scores for juveniles could be interpreted as low juvenile overwintering survival. By fitting Barker models to the same dataset we determined that juvenile site fidelity was lower than that of adults (0.91 and 0.93, respectively), so natal dispersal was slightly greater than breeding dispersal. The high fidelity causes similarity between apparent survival and true survival parameters (S: 0.51 for juveniles, 0.64 for adults). The results are comparable with data from other urban populations. Thus, using robust models certainly allows one to reduce the noise of movements confounding and/or masking survival probabilities, but one can also determine the individual or environmental variables affecting any of them separately.

Agri-Environment Schemes (AES) have been implemented across Europe in an attempt to address biodiversity losses associated with agricultural intensification. For many declining farmland bird species, the reduced availability and suitability of nesting and foraging habitats are thought to play a major role in population declines and some AES have hoped to counteract this by encouraging the provision of such habitats. This study aimed to determine the relative importance of AES on the territory selection of a widespread but declining farmland bird, the Yellowhammer Emberiza citrinella. Yellowhammers were more likely to locate territories in areas containing ‘enhanced margins’; i.e. where field margin habitats were sown with wild flowers and/or agricultural legumes. An average of 0.033 ± 0.008 ha of this ‘enhanced margin’ habitat was present within 100 m of Yellowhammer territories compared to 0.020 ± 0.008 ha within 100 m of random points. This preference may reflect the higher invertebrate chick food abundance associated with this habitat as they contained, on average 46.3% and 36.8% more invertebrate food items than cereal and floral crops respectively. Alternatively, given that chick food abundance was similar between grass and enhanced field margins, this observed preference may be the result of a more open sward structure which increases prey accessibility and improves predator avoidance. Yellowhammers selected territories containing early succession hedgerows, as these constitute the most suitable nesting sites, and preferred territories containing a suitable songpost. Our results suggest that management strategies aiming to conserve breeding Yellowhammers should focus on increasing the coverage of invertebrate rich AES habitats such as floristically-enhanced margins and pollen and nectar plots, and ensure that they are located within typical foraging ranges of cut hedges with elevated songposts.

Recent climate change has a major impact on the sizes and distribution of bird populations, the phenology of their breeding/migration and migratory behaviour (migration distance, migration strategy). We documented changes in the numbers of juvenile Blackcaps migrating in autumn through the S Baltic that were paralleled by changes in wing length of captured individuals during a 43-year study period (1967–2009). We suggest that the observed trends may indicate changing population composition of migrating birds. In the Blackcap, wing length distinguishes among different populations and increases with increasing migration distance of a given population. Available published data show that long-distance and short-distance Blackcaps pass the study region. Hence, we assumed that shorter-winged birds are short-distance migrants wintering in the southern Europe, and that longer-winged individuals are long-distance migrants wintering in the sub-Saharan region. It seems that in 1967–1980 most Blackcap populations declined, but, as wing length slightly increased, the rate of this decline has been higher in the shorter-winged/short-distance Blackcaps. Over the subsequent 24 years alongside with rapidly growing numbers of birds, we noted a remarkable decrease in wing length. This indicates a pronounced increase in the number of short-distance individuals compared to long-distance migrants. Both groups may benefit from improved conditions at their breeding grounds, but the shorter migration route and favourable conditions at wintering sites north of Sahara could favour short-distance migrants over the longer distance and longer-winged Blackcaps.

We assessed the genetic diversity and phylogeography of the Azores Blackbird Turdus merula, based on sequences of two mitochondrial genes (Cytochrome b and NADH Dehydrogenase subunit 2) and one nuclear gene (Aconitase 1 — intron 9) from 45 individuals and an outgroup of 15 birds from Madeira, continental west Europe and north Africa. Our results revealed the lack of genetic structure on these islands and the presence of, at least, two different lineage groups that may indicate two different founder events of the Azores by Blackbirds.

We analyzed the effect of nest temperatures, fledging date, age at fledging, fledgling mass and size on postfledging survival of Great Tits Parus major in eastern Spain. We manipulated temperature during nestling development in 26 nests (average temperature was 39.8, 34.6 and 26.4 °C for heated, control and cooled nest-boxes, respectively), and used radio-telemetry to monitor the survival of 48 nestlings (16 heated, 18 cooled, 14 controls) during the first 15 days after fledging. Heated chicks were lighter than control and cooled chicks. Estimated survival of heated fledglings was lower than that of controls. Additionally, survival of control fledglings increased with size, but this relationship was reversed for heated fledglings. Our results suggest that high temperatures experienced in the nest could have negative consequences on immediate post-fledging survival, and that smaller nestlings may deal more effectively with temperatures surpassing their optimal thermal range.

The Polish breeding population (3,200–3,250 males) of the globally threatened Aquatic Warbler Acrocephalus paludicola represents almost 25% of the global population. Except for the relatively stable large population in the Biebrza valley in north-east Poland less is known about population trends of peripheral populations in western, central and south-eastern regions of the country and whether trends differ depending on region. We investigated the long-term population dynamics in 38 small populations between 1969–2013 in the four Polish regions. Summarizing the trends of all small populations of Aquatic Warblers showed a significant decline in total number of individuals and declining number of populations over time. However, population trends were distinctly different in the different regions, with stable dynamics in south-east, moderate decline in north-east and sharp decline in the central and western regions. During the study period 19 out of 38 populations became extinct (11 populations in the western region, two in central region, four in north-east region and none in the south-east region). Five of these populations were later recolonised thus suggesting a pattern of metapopulation dynamics. To mitigate the negative trends and increased risk of local and regional extinction in the western and central parts of Poland effort should be put to increasing dispersal among populations by increasing the number of stepping stone patches between the viable large eastern populations and the smaller central and western ones.