Pied Flycatchers Ficedula hypoleuca are known to be victims of nest killings in contexts of competition for nest boxes. However, there is only anecdotal information on their opposite role as perpetrators of nest takeovers and occasional killings of other songbirds. Over 31 years we examined whether competition with Great Tits Parus major over nest box ownership is a significant source of mortality for Pied Flycatchers and whether the increase in Pied Flycatcher populations affected the use of nest boxes by the smallest tit species, the Blue Tit Cyanistes caeruleus and Coal Tit Periparus ater, in two forests in the central Iberian Mountain Range. We found 31 Pied Flycatchers killed inside nest boxes. The Great Tit was the most frequent species to which the killings were attributed. Followed by Pied Flycatchers themselves and Nuthatches Sitta europaea. We confirmed the killing by Pied Flycatchers of at least two conspecific males and one incubating female Coal Tit, with one killer male identified. Large increases in population densities of flycatchers after nest box deployment in the two study areas seem to have triggered an intensification of agonistic interactions among their potential occupants, resulting in an increase of takeovers by Pied Flycatchers of nest boxes initially owned by the smallest tit species. Great Tits are not a serious threat for Pied Flycatchers breeding in the study area, most likely due to their preference for natural holes over the nest box types most frequently installed. The interactions of Pied Flycatchers with Blue and Coal Tits for the ownership of nest boxes do not seem to cause significant mortality in the species involved. However, aggressive usurpations of nest boxes by Pied Flycatchers surely have negative impacts on the reproductive success of the victims through their eviction from suitable nesting sites.—Potti, J., Camacho, C., Canal, D. & Martínez-Padilla, J. (2021). Three decades of crimes and misdemeanours in the nest box life of European Pied Flycatchers Ficedula hypoleuca. Ardeola, 68: 315-333.

Many populations of migratory bird species are rapidly declining. As a requisite for targeting effective conservation efforts it is essential to determine the whereabouts of migrants year-round. However, our knowledge of migratory routes and spatial-temporal occurrence across periods of the annual cycle is still limited for most species. We used light-level geolocators to describe in detail the migration system of Barn Swallows Hirundo rustica breeding in southwestern Spain and wintering across West Africa. We were able to successfully retrieve year-round data for 38 individuals and reconstructed their migratory routes using FLightRR package. Many of the studied individuals remained for some time in summer wandering through southern Spain and northern Morocco, a period that we defined as pre-migration. The studied swallows started their autumn migration on average on August 18^th, stopping over to refuel in northwestern Morocco and southern Mali. On average the tagged individuals arrived on September 3^rd at their wintering areas, which were located across Ivory Coast and surrounding countries, in localities dominated by savannahs, grasslands and crops. After wintering, swallows started the spring migration January 26^th on average, stopping over in Senegal and Mauritania. They arrived back at the Spanish breeding colonies February 18^th on average (from mid-January to mid-March). Surprisingly, during the autumn migration, one of the tagged individuals travelled to England before returning south and spending a short wintering period in northwestern Spain.—López-Calderón, C., Magallanes, S., Marzal, A. & Balbontín, J. (2021). The migration system of Barn Swallows Hirundo rustica breeding in southwestern Spain and wintering across west Africa. Ardeola, 68: 335-354.

Bird communities inhabiting tropical rainforests are sensitive to changes in vegetation structure, either natural (e.g. treefalls or landslides) or man-made. Natural changes tend to increase diversity and abundance, whereas anthropic changes often have the opposite effect. We analyse how landscaping for the creation of research facilities influenced the taxonomic, functional and phylogenetic diversity of bird communities in a Caribbean coastal rainforest of Costa Rica, and whether diversity changes were mediated by changes in vegetation structure. Bird communities were sampled by means of mist nets located in the landscaped areas and in paired sites of the nearby rainforest during three consecutive dry seasons (2017-2019). Vegetation structure around each net was also recorded. Forest openness and degree of development of the tree layer led to more abundant and species-rich assemblages in both the managed and the non-managed sites. Functional diversity of several key traits (diet, beak shape, manoeuvrability and foraging site) was favoured by the degree of development of the tree layer in managed sites and by those of the shrub layer in the forest. Beta diversity analyses showed that increased diversity in managed areas was due to a higher presence of species linked to naturally cleared forest areas already present in the forest, rather than to a substitution of a species-poor forest assemblage by a species-rich open-land community. Overall, we show that low-intensity disturbance linked to the creation and maintenance of research facilities can favour the conservation of richer and functionally diverse bird communities, at least in species-rich secondary rainforests, as long as a well-developed tree layer is maintained in the cleared areas.—Aycart, P. & Díaz, M. (2021). Low-intensity landscaping of research facilities increased taxonomic, functional and phylogenetic bird diversity in a lowland rainforest. Ardeola, 68: 355-371.

During spring migration, a few tens of thousands of European Honey-buzzards wintering in sub-Saharan Africa cross the central Mediterranean to reach their breeding grounds in central-eastern Europe. In so doing they concentrate passage through the Sicilian Channel but choose different flyways in response to different wind conditions. This study investigated the influence of local and regional wind conditions on the movement patterns of this species along the Strait of Messina, a migration bottleneck located between eastern Sicily and southern continental Italy where some raptors fall victim to illegal shooting by poachers each spring. Simultaneous observations occurred at four watchpoints, three on the Sicilian side and one on the continental boundary (Calabrian side). Although northwesterly winds prevailed at the Strait during peak migration days, slightly different local patterns of both horizontal and vertical winds at each observation site affected flocking and shaped the passage of raptors through this bottleneck, broadening the migration front. The results confirm that the magnitude of Honey-buzzard spring migration at the Strait is strongly affected by wind patterns in the Sicilian Channel. In particular, migrants concentrate at this bottleneck after crossing the Channel in northwesterly winds the previous day. In conclusion, by interpreting migratory behaviour both at local and regional scales, this work can help to plan more efficient monitoring of Honey-buzzards through the Strait and improving the siting of conservationist efforts. —Agostini, N., Chiatante, G., Gustin, M., Cento, M., von Hardenberg, J., Dell'Omo, G. & Panuccio, M. (2021). Local and regional wind patterns affect spring migration magnitude, flyways and flocking of European Honey-buzzards Pernis apivorus at the Strait of Messina. Ardeola, 68: 373-390.

Habitat specialists, such as forest raptors, are generally more likely to suffer from the impacts of large-scale forestry. One of the most characteristic and controversial aspects of many industrial plantation systems is the use of clearcutting as a harvesting method, which generates a mosaic of highly contrasting land cover types, such as wooded areas adjacent to zones practically devoid of vegetation. We explored the effect of forest cover on the abundance of habitat-generalist and forest-specialist raptors in South-central Chile. During the 2016 to 2018 breeding seasons, we conducted 584 playback surveys at 149 sampling points centred on 3×3km plots within 9×9km squares. The Rufous-legged Owl Strix rufipes, a forest specialist, showed a positive relationship with forest cover at the local scale. However, we found no significant relationships for other forest specialists in this study. Most habitat-generalist species showed a negative or non-linear relationship with forest cover, with greater species abundances observed in landscapes with intermediate levels of forest and open areas. Interestingly, the models with the highest statistical support included total forest cover (native forest + plantations) as a predictor, suggesting that the habitat-generalist species did not significantly discriminate between natural and artificial forests. Our results show that both generalist and forest-specialist raptors can use landscapes dominated by exotic plantations in South-central Chile.—Santander, F., Alvarado O., S. & Estades, C.F. (2021). Effect of forest cover on raptor abundance in exotic forest plantations in Chile. Ardeola, 68: 391-408.

Diet specialisation during brood rearing has important consequences on parental reproductive success and on the recruitment rate of offspring. However, very little is known about the long-term consistency of parents when feeding their offspring. Here, we used Mediterranean Great Tits Parus major to test the hypothesis that parents show a consistent level of individual specialisation across years. To do this, we recorded prey delivered to 10-14 day-old chicks over six years. We standardised the data to control for environmental factors and used a Principal Component Analysis (PCA) to characterise the foraging provisioning behaviour of individuals. We assessed long-term dietary consistency using data from individuals recorded in two different years by performing a repeatability analysis (absolute consistency) and also running a Generalised Linear Mixed Model, where we measured the consistency of position of individuals in a group, relative to others (relative consistency). The PCA analysis showed that diet selection when provisioning chicks varies across two gradients: prey size vs. frequency of prey delivery, and caterpillars vs. spiders. Controlling for these factors, we found that both individual repeatability and the correlation of diet choices between years were moderately significant. Although Great Tits show high individual dietary specialisation within a year, diet fluctuates to some extent across years. This could provide a degree of flexibility to parents dealing with highly fluctuating environmental conditions as well as a buffer against climate change, and could be a consequence of increasing lifetime experience.—Olivé-Muñiz, M., Pagani-Núñez, E. & Senar, J.C. (2021). Breeding Great Tit Parus major individuals have moderately consistent foraging niches across years. Ardeola, 68: 409-422.

The absence of sex dimorphism in many bird species complicates sex determination by direct observation, hindering sex-specific studies. Standard protocols for molecular sexing include polymerase chain reaction (PCR) amplification of intron regions of the Chromodomain-Helicase DNA-binding protein 1 (CHD1) gene. While several methods have been studied, their usefulness for songbirds (Passeriformes) has not been consistent and has largely depended on target species and on time-consuming primer-set specific optimisation of available protocols. We tested a molecular sexing protocol with two universal primer sets (P2/P8 and 2550F/2718R) in a corvid songbird: the Plush-crested Jay Cyanocorax chrysops. The protocol was rapid and inexpensive as well as highly effective. Using 2550F/2718R, females were revealed by two bands separated for some 200 base pairs (bp) that resolved easily on 0.8% agarose gel. Conversely, P2/P8 female amplicons differed in roughly 30 bp and a more expensive 3% agarose gel was necessary to reveal them. Our results are contextualised with an up-to-date literature survey of molecular sexing in other corvids. The primer set 2550F/2718R is found to be effective, providing a reliable and low-cost method for sexing jays and other corvids. —Lois-Milevicich, J., Gómez, R.O., Ursino, C.A., Lois, N.A. & de la Colina, A. (2021). Rapid and low-cost molecular sexing of a corvid songbird using a single protocol with two universal primer sets. Ardeola, 68: 501-510.

Smell plays an important role in the sensory ecology of birds. Although birds are considered to rely mainly on sight and hearing, use of smell in the reproduction, communication and foraging behaviours of many birds has been documented. However, there is very little information about the role of smell in foraging by nectarivorous birds. We tested the ability of the Amazilia Hummingbird Amazilia amazilia s. l. to use olfactory signals during foraging. Individuals were exposed to two feeders, one of which emitted a floral essence. Contrary to our expectations, no significant differences were found in the choice of feeders based on their odour. Our results suggest that neither male nor female Amazilia Hummingbirds use smell in the search for food but employ other senses, mainly sight. —Núñez, P., Méndez, M. & López-Rull, I. (2021). Can foraging hummingbirds use smell? A test with the Amazilia Hummingbird Amazila amazilia. Ardeola, 68: 433-444.

The next reform of the EU Common Agricultural Policy (CAP) for the period 2021-2027 (currently extended to 2023-2030) requires the approval by the European Commission of a Strategic Plan with environmental objectives for each Member State. Here we use the best available scientific evidence on the relationships between agricultural practices and biodiversity to delineate specific recommendations for the development of the Spanish Strategic Plan. Scientific evidence shows that Spain should (1) identify clear regional biodiversity targets and the landscape-level measures needed to achieve them; (2) define ambitious and complementary criteria across the three environmental instruments (enhanced conditionality, eco-schemes, and agri-environmental and climate measures) of the CAP's Green Architecture, especially in simple and complex landscapes; (3) ensure that other CAP instruments (areas of nature constraints, organic farming and protection of endangered livestock breeds and crop varieties) really support biodiversity; (4) improve farmers' knowledge and adjust measures to real world constraints; and (5) invest in biodiversity and ecosystem service monitoring in order to evaluate how the Plan achieves regional and national targets and to improve measures if targets are not met. We conclude that direct assessments of environmental objectives are technically and economically feasible, can be attractive to farmers, and are socially fair and of great interest for improving the environmental effectiveness of CAP measures. The explicit and rigorous association of assessments and monitoring, relating specific environmental indicators to regional objectives, should be the main criterion for the approval of the Strategic Plan in an environmentally-focused CAP 2023-2030.—Díaz, M. et al. (2021). Environmental objectives of Spanish agriculture: scientific guidelines for their effective implementation under the Common Agricultural Policy 2023-2030. Ardeola, 68: 445-460.