El mochuelo europeo Athene noctua es una pequeña rapaz nocturna asociada a paisajes agro-pastoriles abiertos que actualmente se enfrenta a un claro declive de sus poblaciones. Un exhaustivo estudio realizado en 1998 en Bizkaia (suroeste de Europa) detectó 272 territorios de mochuelos, de los cuales el 10,5% había desaparecido en 2009. Los censos parciales posteriores sugieren que la tendencia a la disminución ha sido aún mayor en los últimos años. Con el fin de determinar su distribución actual se llevó a cabo una campaña de muestreo en toda Bizkaia entre marzo y junio de 2024. Se muestrearon 280 puntos en 1633 ocasiones, de los cuales se detectaron un total de 94 territorios activos, lo que representa una ocupación actual del 33,57%. De los 272 territorios encontrados en 1998, 206 fueron muestreados de nuevo en este estudio, de los cuales 55 están ocupados actualmente, representando un descenso poblacional del 73,30% entre 1998 y 2024. Se desarrollaron modelos lineales generalizados (GLM) y análisis de escalamiento multidimensional (NMDS) para determinar qué variables relacionadas con el paisaje y el cambio en el uso del suelo afectan a la presencia de la especie. Se detectaron la altitud y el aumento de la urbanización y el número de carreteras en la zona como variables con un impacto negativo, mientras que la presencia zonas de pradera, así como la densidad pasada de territorios, afectaron positivamente a la presencia actual. Aunque estos modelos apuntan a algunas variables significativas, gran parte de la tendencia observada no puede explicarse a través de los factores analizados. Esto puede deberse a que la tipificación de usos del suelo utilizada para modelizar el cambio en el paisaje puede estar omitiendo información sobre el manejo del suelo a menor escala. Por ejemplo, las zonas agrícolas que se mantienen agrícolas a lo largo de los años pueden estar sometidas a una gestión más intensiva (turnos de siega más frecuentes, mayor uso de insecticidas, etc.) que no se refleja en los modelos. Para comprender los mecanismos que subyacen a las tendencias observadas sería necesario estudiar los cambios en la gestión del paisaje a menor escala.—FernándezÁlvarez, A., Parra-Ligero, P., Azkona, A., Apraiz, I., Zuberogoitia, I. y Zabala, J. (2026). Estimación de una población del mochuelo europeo Athene noctua y de factores asociados con su disminución bidecadal. Ardeola, 73: 45-64.
Comprender la dispersión y la supervivencia es esencial para interpretar la dinámica de las poblaciones de aves, aunque estos parámetros siguen desconocidos para muchos taxones, incluyendo especies localmente abundantes. La collalba negra (Oenanthe leucura) está experimentando un declive poblacional generalizado, a pesar de seguir siendo común en partes del sur de España. La supervivencia y ecología del movimiento de la especie sigue siendo en gran medida desconocida. Aquí presento el primer estudio de la supervivencia y la dispersión reproductiva en la especie, basada en 58 adultos (32 machos y 26 hembras) marcados con anillas de colores durante la temporada de cría de 2021 en Alicante (España). Como adultos se consideraron a las aves sexualmente maduras, es decir, aquellas en su segundo año calendario y las de mayor edad. Los territorios fueron revisados durante las temporadas de cría de 2022 a 2024 para determinar la persistencia y los movimientos de los individuos. Se volvieron a observar 22 machos (69% de las aves anilladas) y 14 hembras (54%) entre 2022 y 2024, lo que proporcionó 35 y 24 registros de dispersión interanual, respectivamente. La dispersión reproductiva no difirió entre sexos y fue limitada, con distancias medianas < 70 m y con el 75% de los avistamientos ocurriendo en el mismo territorio (< 250 m) que el año anterior. A pesar de haber seguido las aves en seis localidades distintas, con una distancia máxima entre localidades de 15 km, todos los movimientos ocurrieron dentro de cada localidad, y solo dos individuos, un macho y una hembra, se desplazaron más de 750 m. La fidelidad de pareja fue alta, con siete parejas permaneciendo juntas varios años y un solo caso de divorcio (12,5%). Las estimaciones de supervivencia fueron altas y no difirieron entre sexos, con valores medios de 0.66 para machos (ES = 0.07) y hembras (ES = 0.06). En conjunto, los adultos de collalba negra en España oriental han mostrado una alta fidelidad al territorio, distancias cortas de dispersión y altas tasas de supervivencia. Estos resultados proporcionan el primer estudio sólido de la dispersión y la supervivencia en la especie, lo que puede servir como referencia para evaluar futuras necesidades de conservación de esta ave en declive. Investigaciones futuras deberían centrarse en caracterizar los patrones de dispersión y la supervivencia de las aves juveniles, que siguen siendo desconocidos para esta especie.—Pérez-Granados, C. (2026). Dispersión reproductiva, tasa de divorcio y supervivencia adulta de la Collalba negra Oenanthe leucura en el este de España: sin diferencias entre sexos. Ardeola, 73: 101-112.
The Eurasian Stone-curlew Burhinus oedicnemus is a steppe bird distributed in Europe, Asia and North Africa. Although not globally threatened, it is considered a species of European conservation concern. The Grosseto province is one of the most important areas for Stone-curlews in Central Italy. Previous studies there have found that this population is largely resident and therefore suitable for assessing long term population trends. We carried out this study from December 2013 to January 2023, surveying all known winter roost sites annually. Our estimate shows that over the past ten years, the population has remained relatively stable, with no significant increasing or decreasing trend. However, both the raw survey data and the predicted values from a GAMM model, developed to estimate the global trend, reveal considerable fluctuation in the count data. For this reason, and given the elusive behaviour of the species, it is difficult to produce an accurate estimate of the minimum and maximum number of birds wintering in the Grosseto area. Nonetheless, maximum counts of 500-600 birds suggest that this may be approximately the size of the wintering Stone-curlew population. In addition, ten GPStagged birds were studied to outline their roosting behaviour. These data helped to explain the observed variability in the counts. Stone-curlews exhibited two contrasting behaviours: they showed remarkable fidelity to certain roosting areas that were regularly used over multiple years, but they also displayed notable mobility between different roosts, occasionally occupying new sites not previously used. Overall, the incidence of disturbance factors was low but warrants further investigation. Recent agricultural changes in Grosseto-particularly the expansion of vineyards and the decline of traditional farming-appear to be partially exploited by Stone-curlews, which frequently used vineyards as winter roosts. However, the conservation value of these habitats remains uncertain, especially given their potential negative impacts during the breeding season.-Dragonetti, M., Falchi, V., Farsi, F., Giunchi, D., Passalacqua, L., Picciau, A. & Giovacchini, P. specialIntscript Stone-curlews Burhinus oedicnemus win-tering in Grosseto province (Central Italy): status, habitat use and possible threats. Ardeola, 73: 3-21.
Understanding the migratory movements and habitats utilised during the annual cycle of migratory birds is essential for developing comprehensive conservation strategies. The Kentish Plover Anarhynchus alexandrinus is a small shorebird with a broad distribution across different continents, with both resident and migrant populations. Despite this broad range, the species faces increasing threats from habitat loss and human disturbance, particularly in southern Europe, where significant population declines have been reported. However, detailed knowledge of their migration routes and stopover sites remains limited, hindering the assessments needed to develop effective year-round conservation actions. In this study, we provide the first high-resolution GPS tracking of a full migratory journey by a Kentish Plover breeding in Cadiz, southwest Europe. This female individual overwintered for 162 days in Diawling National Park in southwestern Mauritania, occupying a wintering home range exceeding 20,000ha-substantially larger than during the breeding (69 days, similar to 90ha) and post-breeding (68 days, similar to 200ha) periods. Both the autumn and spring migrations were similar in duration and distance, covering approximately 2,500km in about seven days, but flying faster and at higher altitudes during spring. In autumn, it made a single, longer stopover, while in spring it stopped twice at Ramsar-designated wetlands, with shorter and more closely spaced stopovers. Although based on a single individual, our results offer valuable insights on the migration performance of this species. In particular, this is the first high-resolution documentation of a transcontinental migration in this species, high lighting the importance of identifying and conserving key non-breeding and stopover habitats across its migratory range.
In many bird species, successful breeders remain faithful to their previous nesting sites, benefiting from site familiarity and increased reproductive success. Differences between males and females in movements and breeding effort offer an opportunity to explore sex-specific effects on site fidelity and reproductive success. This study examined whether the decision of Common Kingfishers Alcedo atthis to disperse from or remain at a previous breeding location depends on past breeding success. We also explored whether breeding performance improved from one year to the next for the birds that returned. Between 2014 and 2018, we monitored two Common Kingfisher breeding populations: one in the Danube River system in southwestern Slovakia and another in the Central Bohemian, South Bohemian and Highland regions in Czechia. During this period, we ringed 353 adult kingfishers and recaptured 53 in subsequent years. For 34 returning adults, we documented breeding success over two consecutive years, and for eight adults, over three seasons. Breeding site fidelity was relatively low (similar to 13%), and mate fidelity even lower (2%), likely reflecting the partial migratory behaviour of females, which either do not return to their previous breeding territories or, if they do, may arrive after their mate from the previous years has already paired with another female. Notably, none of the 19 adults that failed to produce broods in one season returned the following year, whereas 34 of 326 (10%) successful breeders did return. Females that fledged a larger number of offspring were more likely to return. This pattern suggests that high food availability may mitigate the costs of intensive breeding on survival and site fidelity or, alternatively, that these successful females are high quality individuals. Furthermore, although males exhibited higher return rates than females, only returning females improved breeding performance in the subsequent season. These findings highlight the interplay between breeding success, site fidelity and parental investment strategies.
.-the gut microbiome is an important mediator of life-history traits in animals and performs essential functions that may allow hosts to exploit novel niches. However, sources of variation in microbiome abundance and composition within vertebrate species are poorly understood, particularly in wild birds. Here we used 16S rRNA gene sequencing to describe the faecal microbiome of a trans-Saharan migratory passerine species breeding in Central Spain, the European Pied Flycatcher Ficedula hypoleuca. We investigated differences in microbial composition and diversity between the natural habitat of the species (oak forest) and a newly created habitat (pine forest) located only 1km apart. We sampled both adult males and females, as well as nestlings (13 days old). The results showed a dif-ference in the composition of microbiomes of birds between the habitats, with birds from the oak forest showing a higher abundance of bacterial taxa, such as Actinobacteriota and Proteobacteria, and birds from the pine forest showing a higher abundance of Verrucomicrobiota. We observed no differences in microbial composition according to sex or age, although nestlings and breeding females showed a higher abundance of certain bacteria, especially in the oak forest. We also investigated differences in metabolic functions of the microbiome and detected a higher relative abundance of bacteria with fatty acid biosynthesis and degradation pathways, as well as metabolite precursor and energy generation pathways in birds from the oak forest. In the pine forest, we found a higher abundance of bacteria with the L-alanine biosynthesis and pentose phosphate pathways. Our study improves our understanding of the gut microbiome composition of insectivorous migratory passerines and shows that breeding habitat can be a key modulator of avian gut microbiome composition.-Videvall, E., Ruiz-Lim & oacute;n, P., Martinez-Padilla, J., Moreno-Indias, I., Canal, D. & Muriel, J. (2026). Fine-scale variation in the gut microbiome of the European Pied Flycatcher Ficedula hypoleuca in Central Spain. Ardeola, 73: 23-42.
Birds are key ecosystem service providers given the wide range of services in which they are involved, their outstanding mobility and large population sizes. However, we lack a comprehensive framework to evaluate the ecosystem services (ES) provided by bird species at large spatial scales. Here, we introduce ServiBirds, an innovative database meticulously designed to quantify the ES delivered by bird species, using Spain, a species-rich country, as our study model. The database describes the species-level values in 12 different provisioning, supporting/regulating and cultural ES for 378 bird species from 73 families. For each species, the supporting/regulating services were weighted by its field metabolic rate and its population size in Spain, to enable a more precise view of the current role of the species in such services. In addition, birds provide diverse other ES, especially aesthetic, ecotouristic, as pest controllers and as seed dispersers. The most important providers of supporting/ regulating services in Spain included some, such as the Eurasian Magpie Pica pica and the Common Blackbird Turdus merula, that provide several services and specialists, such as the Griffon Vulture Gyps fulvus, that provide a single service. For cultural services, the top species were those, such as the Red-legged Partridge Alectoris rufa, Golden Eagle Aquila chrysaetos or European Goldfinch Carduelis carduelis, that provide multiple services. Our study underlines the important role that birds play in ecosystem conservation and for human wellbeing. Moreover, the proposed framework can be adapted to other regions, and even taxonomic groups. We hope this study acts as a catalyst to better understand and evaluate the ES provided by birds, thereby serving as a tool for bird conservation and ecosystem management.-Sebasti & aacute;n-Gonz & aacute;lez, E., Carri & oacute;n, S., P & eacute;rez-Granados, C., L & oacute;pez-Iborra, G.M., Botella, F., P & eacute;rez, C., Rocher, G., P & eacute;rez-Garc & iacute;a, J.M., Garc & iacute;a-Rodr & iacute;guez, J., S & aacute;nchez-Zapata, J.A. & Orihuela-Torres, A. (2026). Servibirds: Servibirds: Quantitative assessment of the ecosystem services provided by native birds in Spain.
-Patchy distributions associated with specialised habitats often lead to vocal variation and, ultimately, speciation. We investigated the influence of spatial structure on vocal divergence among populations of two Synallaxis species. S. frontalis has an extensive and continuous distribution, whereas S. hellmayri is endemic to the Brazilian Caatinga and exhibits a restricted, disjunct distribution. The two species co-occur in sympatry in parts of northeastern Brazil. We measured seven parameters of the bisyllabic pair-contact call (BPCC) at 21 localities where both species were present. Spatial patterns were quantified using distance-based Moran eigenvector maps (MEMs), which were then used as spatial predictors in a distance-based redundancy analysis (db-RDA) to assess vocal divergence among populations. We found that variation in the BPCC of S. hellmayri was significantly associated with spatial predictors, with geographically distant populations showing greater acoustic divergence. These results indicate that acoustic differentiation in S. hellmayri is consistent with isolation by distance. Thus, the observed vocal divergence reflects spatial structuring across its fragmented range, providing novel evidence of how geographic isolation shapes intraspecific communication in a suboscine species.-Oliveira, H.S., dos Santos-J & uacute;nior, E.V. & dos Anjos, L. (2026). Divergent spatial patterns of acoustic variation in the Red-Shouldered Spinetail Synallaxis Hellmayri and the Sooty-Fronted Spinetail S. Frontalis (Furnariidae). Ardeola, 73: 81-91.
La Sección Bibliográfica de Ardeola publica reseñas breves de publicaciones recibidas en la biblioteca de SEO/BirdLife. Estas reseñas se realizan desinteresadamente por un conjunto de colaboradores. Las reseñas son normalmente solicitadas por los editores a los colaboradores, aunque otras adicionales pueden ser consideradas para su publicación. Las reseñas expresan las opiniones de los revisores, de modo que no reflejan necesariamente la opinión de los editores o de SEO/BirdLife.
organochlorine pesticides are environmental contaminants showing high toxicity, volatility, persistence and bioaccumulation on the environment and organisms. These compounds can affect vertebrate immune systems, rendering animals more susceptible to infections but can also reduce parasitic infections by decreasing the populations of vectors transmitting parasites. Here we studied the presence and variation of organochlorine pesticides in feathers of several tropical bird species of the Dominican Republic from three different sampling areas. In addition, we obtained data on blood parasite infections of these birds to investigate potential interactions between parasites and pesticides. Feather samples from different individuals of the same species and sampling area were pooled to reach the minimum mass needed for the pesticide analyses. In total 31 samples were analysed: 12 of from ten individuals, six of Red-legged Thrush Turdus plumbeus from nine individuals, six of Common Ground-dove Columbina passerina from 20 individuals, one of Banaquit Coereba flaveola from 22 individuals and two of Hispaniolan Mangos Anthracothorax dominicus from 19 individuals. We found 11 different organochlorine pesticides (concentrations ranging from 0.02 to 25.52ng/g). In addition, five different blood parasite types were detected by molecular analyses in samples from 128 individuals of bird species (all except the Mango hummingbirds). Blood parasite presence varied among bird species. However, we did not detect any significant interaction between pesticide accumulation and blood parasite infection in data from the four more abundant bird species in the sample. Pesticides banned in the Dominican Republic more than 20 years ago are still detected in groups of feathers from all the bird species and areas analysed although there were no significant differences in their concentration between species or sampling areas.-Ca & ntilde;izares-Lara, C.M., Espin, S., Garcia-Fern & aacute;ndez, A.J., Martinez, J., Navas, I., Garcia-del Rio, M. & Merino, S. (2025). Bioaccumulation of organochlorine compounds and infection by blood parasites of birds from Hermanas Mirabal Province, Dominican Republic. Ardeola, 72: 311-327.
.-Animal ethics in wildlife monitoring is receiving increasing consideration from scientific institutions. Mist nets are the most commonly used technique for trapping birds in studies; however, catching wild animals inevitably causes them stress. Trapped birds experience stress throughout the ringing process, from the moment they enter the net until their release. Monitoring Reed Buntings Emberiza schoeniclus during winter presents an additional constraint: birds are typically caught at dusk, upon arrival at their communal roost. According to ringing recommendations, birds captured early at the roost can be released before dusk, while those captured later must be kept safely overnight and released the following morning to avoid increasing the risk of predation due to inadequate roost location by night-released birds. In the present study, we (i) investigate the stress development in birds during the ringing process, focusing on its variation over time after trapping through measurements of heart rate and breathing rate, and (ii) assess the impact of three release protocols on stress-related behavioural indices and the return rate to the wintering roost. The results indicate that heart and respiratory rates are highest when the bird is held in the hand, supporting the idea that restraining birds in darkness allows them to calm down. Our measurements confirm that the handling process is highly stressful for birds, resulting in significantly elevated stress levels compared to their daily baseline
