In the Amazon, the construction of hydroelectric dams is an emergent driver of biodiversity loss, creating numerous land-bridge islands, most of them unable to sustain an assemblage of bird species comparable to the intact forest. Although we understand the effects of forest fragmentation on species richness and distribution, we still need to uncover the physiological mechanisms underlying the success of organisms living in disturbed habitats. In this study, we used feather corticosterone levels as a measurement of physiological indicators of stress, evaluating whether corticosterone levels mirror the effects of habitat fragmentation on species occurrence. Since data suggest that smaller islands can reduce habitat suitability, increasing stress in birds that live within them, we predicted that birds living in smaller islands would present increased feather corticosterone levels. We captured birds in 13 islands of varying size and in two continuous forests and analysed feather corticosterone levels of 265 individuals from eight different species. Overall, our findings did not support the hypothesis that corticosterone varies in relation to island size, except for the Guianan Antwarbler Hypocnemis cantator, which presented the predicted pattern: decreasing feather corticosterone levels with increasing island size. These differences suggest that species respond differently to stressors driven by fragmentation. Further studies are necessary to assess the reliability of corticosterone levels as a physiological measurement of stress and to determine which parameters are useful to understand how insularisation caused by human activities may influence the resistance of avian populations to habitat disturbances. —Bicudo, T., Anciães, M., Arregui, L. & Gil, D. (2020). Effects of forest fragmentation on feather corticosterone levels in an Amazonian avian community. Ardeola, 67: 229-245.

The Spanish Castilla y León region is one of the most important wintering areas in Europe for the Red Kite Milvus milvus. At the same time, the steepest population declines of Red Kite have been recorded there, electrocution by power lines being one of the main causes. Thus, knowledge about the annual spatio-temporal ecology of this raptor, and its relationship to electrocution events, is necessary to develop effective conservation measures. Distribution models for the breeding and wintering populations of the Red Kite in Castilla y León were developed, considering climate, topography and land uses, to analyse the potential spatial variation between them. Models for electrocution risk also considered the technical characteristics of the power poles to determine their impact on electrocution events in both seasons. Our results show two different areas are used seasonally: 1) an important wintering area in the centre of the region, characterised by crop zones, moderate temperatures, rubbish dump sites and human presence, and 2) a nesting area in the south of the region, in which the availability of livestock carcasses, low levels of precipitation, distance from landfills and gentle relief were the most influential variables. The electrocution risk model indicates that the most suitable areas for Red Kite reproduction are also those that are most risky, including power poles of the most dangerous types; those with straight or vaulted cross-arms. Finally, the theoretical approach presented here provides a framework for the design of management and control measures aimed at minimising Red Kite electrocutions in the northern half of the Iberian Peninsula. —Crespo-Luengo, G., Hernández-Lambraño, R.E., Barbero-Bermejo, I. & Sánchez-Agudo, J.A. (2020). Analysis of spatio-temporal patterns of Red Kite Milvus milvus electrocution. Ardeola, 67: 247-268.

Understanding ecological factors and processes affecting the abundance of species of conservation concern is key to ensuring their conservation. The Eurasian Oystercatcher Haematopus ostralegus is a ‘Near Threatened’ wader species that depends on coastal zones during the non-breeding season. However, these habitats constitute focal points of human settlement and suffer from intensified human activities. I used survey data from the central part of the Gulf of Gabès, Tunisia, to assess the significance of ecological and anthropogenic factors as predictors of the density of wintering oystercatchers. Using generalized linear mixed models, Oystercatcher density was positively correlated with sediment mud content and negatively correlated with seagrass cover. Density was also positively correlated with distance from human settlements and negatively correlated with the densities of recreationists and artisanal fishermen. Overall, oystercatchers avoid intertidal areas near human settlements. This study provides critical information on where conservation and research efforts should be focused to preserve this wader species. As a priority, investigations on flight initiation distances are needed to determine at which spatial level it would be beneficial to create buffer zones or walkways to minimise the negative impact of human disturbance on this wintering population.— Hamza, F. (2020). How habitat features and human activities shape occurrence of the declining Eurasian Oystercatcher Haematopus ostralegus on a Mediterranean coastline. Ardeola, 67: 269-284.

Long-term monitoring of endangered birds is essential to estimate population trends and to identify potential causes of population decline. This is particularly important for alpine birds inhabiting mountain areas at the boundaries of their range. Here we analyse the population trend of Capercaillie in the Spanish Central Pyrenees based on annual surveys carried out between 2000 and 2017. We found a significant population decline (around 58%) in the number of birds counted in leks. Most capercaillies inhabit coniferous forests of Black Pine with abundant Bilberry and Rhododendron understorey. The number of males declined at lower altitudes and in more exposed orientations, in a scenario consistent with the differential rate of loss of habitat quality due to climate change. We hypothesised that one of the main causes of the Capercaillie decline could be low breeding success (average annual productivity 0.67 chicks per female). In light of the decline rates observed, the Pyrenean population should be relisted as endangered in the Spanish National Catalogue of Endangered Species. Affording a higher degree of protection should guarantee the adoption of management measures to reverse or slow down the general trend of decline of the species in the south of its range.—Gil, J.A., Gómez-Serrano, M.Á. & López-López, P. (2020). Population decline of the Capercaillie Tetrao urogallus aquitanicus in the Central Pyrenees. Ardeola, 67: 285-306.

Habitat loss and landscape fragmentation are important drivers of changes in biodiversity. In fragmented landscapes, bird species are able to use multiple forest patches that may therefore share an important portion of the regional biodiversity. In turn, these patches are linked through their shared bird diversity (i.e. species-habitat networks). Identifying the importance of nodes (e.g. forest patches) in species-habitat networks is increasingly important to improve conservation planning. Within this network approach, the relative importance of patches for birds can be identified via centrality indices-measures of the magnitude of shared bird diversity of patches across the entire network (i.e. patch centrality). Here, we tested for changes in patch centrality within bird species-patch networks of two habitat guilds, forest specialists and generalists, in relation to patch area, patch shape irregularity and within-patch habitat characteristics across 15 Polylepis woodland patches in a páramo landscape of southern Ecuador. Patch centrality for forest specialists decreased with greater influence of surrounding páramo plants, i.e. an increasing proportion of bunch-grasses and small shrubs, in the within-patch habitat and was unaffected by either patch area or patch shape irregularity. On the other hand, patch centrality for generalists was positively influenced by patch shape irregularity but was unaffected by patch area or the influence of surrounding páramo plants in the within-patch habitat. Patch centrality reveals that the relative importance of Polylepis woodlands lies in their habitat quality. Forest specialists are dependent on mature Polylepis woodland patches, while generalists benefit from the natural irregular shape of the woodlands. Finally, a species-habitat network approach facilitates the recognition of important Polylepis patches and their characteristics for conservation of the Andean bird community at a landscape scale.—Astudillo, P.X., Grass, I., Siddons, D.C., Schabo, D.G. & Farwig, N. (2020). Centrality in species-habitat networks reveals the importance of habitat quality for high-Andean birds in Polylepis woodlands. Ardeola, 67: 307-324.

The carotenoid-based colouration that many birds present may honestly reflect the quality of the bearer, as carotenoids have to be obtained through diet. These pigments are important for many physiological functions and individuals could find a trade-off between the allocation of carotenoids for these uses and their accumulation for secondary-sexual and social traits. The Yellow-legged Gull Larus michahellis is an opportunistic species that feeds on a wide spectrum of prey. We studied whether carotenoid-based colouration (bill, red spot, eye-ring) is related to the trophic ecology inferred by the isotopic composition of adults' feathers at three colonies of this species. The isotopic marker δ¹³C negatively correlated with carotenoid-based colouration (red spot area). Contrarily to a priori prediction, the marker indicated that higher consumption of landfill scraps and terrestrial prey might lead to a larger red bill spot in adult Yellow-legged Gulls independently of sex. No correlation was detected between isotopic signatures and egg volume in females. The finding that higher consumption of marine prey may imply a smaller red spot supports some results from other avian studies that report that feeding on human-related terrestrial food sources has an apparently positive effect on the adult phenotype. The results may suggest that higher consumption of marine prey may not be as advantageous as supported by previous studies. Nonetheless, the effects of potentially toxic compounds that may come from some feeding sources should be further studied, including any delayed sub-lethal effects on the physiology of adults and, probably, chicks. —Zorrozua, N., Alonso-Álvarez, C., Diaz, B., Sanpera, C., Jover, Ll. & Arizaga, J. (2020). Carbon δ¹³C isotopic marker values correlate with carotenoid-based bill colouration in adult Yellow-legged Gulls Larus michahellis. Ardeola, 67: 325-339.

There is a strong relationship between bird wing morphology and flight style. Wing shapes are related to manoeuvrability, flight speed, energetic costs during flight and take-off speed. Wing shape differences among species have been frequently studied but differences can also be found within species, between sexes and age groups. Many studies have assessed differences in wing shape between juveniles and adults in different passerine species but little is known about such differences in other bird orders. Performing a Size Constrained Components Analysis (SCCA) and a graphical approximation, we analysed the wing shape of juveniles and adults of eight species, including four passerines and four non-passerines of three different orders. According to a graphical approximation, we observed that wing shape differences between age groups differ among species. In the non-passerine species considered, juveniles have more pointed and concave wings than adults. In contrast, in the four passerine species, juveniles have more rounded wings than adults. However, the results for the C2 axis of SCCA (index of pointedness) do not completely agree with the graphical approximation. Our results showed that the C2 axis does not represent the same vector of wing shape variation in all species. The contribution of changes in C2 to variation in wing pointedness seemed to depend on the position of the wing tip, which is a good index of pointedness only when the wing tip is in the two most distal primary feathers. Surprisingly, the adults of some species do not have longer wings than the corresponding juveniles, because the feathers that define the wing tip do not grow longer during the first complete moult. We discuss the role of the first complete moult in changing the shape of juvenile wings into adult wings, and the implications of our results for the analysis of bird wing shape.—Cabodevilla, X., Pérez-Tris, J., Moreno-Zarate, L., Pérez-Rodríguez, A., Lima-Barbero, J.F., Cruz Camacho, M., Villanua, D., Ibáñez, R., Gerboles, A. & Arroyo, B. (2020). Age-related variation in wing shape differs between bird orders: implications for interpretation of the pointedness index (C2 axis) in a size-constrained principal component analysis (SCCA). Ardeola, 67: 341-354.

Owls, like other secretive species, are difficult to detect. During the last few decades, protocols used for surveying owls have revealed the best methods to acquire accurate data about their distribution and abundance. However, these protocols were established by testing the response of owls to playback of broadcast calls, using wild, unknown individuals that were only noticeable when vocalisations were given/detected. Therefore, there is no clear consensus on the best method to survey owls. We tested a protocol to survey Tawny Owls Strix aluco using 20 radio-tracked individuals in two study areas with contrasting owl density. We conducted 58 survey tests during winter 2014-2015. In the two study areas respectively, 61.3% and 70.4% of the target individuals responded, on average, within the first six minutes after the start of call playback. Naïve occupancy estimates were 67.7% and 85.2%, respectively, considering the combined responses of the target individual and its mate. We detected a movement of the target owls from their original position towards the playback source on 72.4% of the sampling occasions in both areas. Tawny Owls approached within 50m of the playback point on only 56.9% of occasions. Mates or neighbours responded to broadcast calls more often in the high-density area than in the low density one. The detection probability of target owls increased more than fourfold when their mates joined in defence of the territory, and also increased fourfold when the target individuals approached the broadcast point and when we increased the playback period from five to fifteen minutes. We recommend two 15-minute periods of call playback per point and year, on dry and calm winter nights, at survey points one kilometre apart.—Zuberogoitia, I., Burgos, G., González-Oreja, J.A., Martínez, J.E., Morant, J. & Zabala, J. (2020). Testing detectability of radio-tracked Tawny Owls using playback broadcast surveys: designing evidence-based surveys. Ardeola, 67: 355-369.

Timing of reproduction is a critical life-history trait and implies major fitness consequences. Differences in life history strategies can lead to different responses to the same environmental conditions even among closely related species. Investigating the factors affecting the timing of reproduction in closely related and sympatric species may help understanding the relationship between different life history traits and species-specific responses to ecological factors. We investigated the effects of season (photoperiod), local climatic variability and prey abundance on the breeding season of two sympatric insectivorous birds that differ in the timing of reproduction and moult and have different migration strategies: the Moustached Warbler Acrocephalus melanopogon and the Eurasian Reed-warbler Acrocephalus scirpaceus. During a five-year period, breeding phenology was determined by examining bird incubation patches during standardised captures and food availability was assessed by invertebrate sampling. Time, mean temperatures and the abundance of some prey taxa were inter-correlated and all contributed to influence the breeding phenology of both species according to partial least squares regression analysis. Besides some interspecific differences in the effect of environmental factors on the breeding phenology, we found strong similarities between the patterns observed in the two warblers. This suggests that, in spite of interspecific differences in life history, the ecological mechanisms shaping reproduction phenology are similar in the two warblers and the same environmental factors are involved in determining the timing of their reproduction.—Ceresa, F., Belda, E.J., Brambilla, M., Gómez, J., Mompó, C. & Monrós, J.S. (2020). Factors shaping breeding phenology in birds: an assessment of two sympatric Acrocephalus warblers with different life histories. Ardeola, 67: 371-385.

Oscine passerine birds learn their songs principally through cultural transmission. However, habitat fragmentation might induce cultural variation in song, leading to restrictions in the transmission of cultural information. In this study, we aim to evaluate individual responsiveness to conspecific vocalisations within and between two nearby bird populations to assess within-species behavioural changes with distance. To do so, we used song playbacks of'Elepaio Chasiempis sandwichensis in a fragmented landscape on the north-east slope of Mauna Loa Volcano (Hawaii Island, USA). We evaluated the response of'Elepaio males to songs recorded in their own populations and to those recorded in another population. We also compared vocalisations between both populations to assess acoustic differentiation. Our results indicate behavioural divergence in song responsiveness over a small spatial scale for this species as well as significant differences in acoustic traits. However, contrary to what was expected,'Elepaio individuals from both populations did not vary in their response pattern to songs depending on their origin. This suggests that acoustic differentiation may not be strong enough to drive behavioural divergence in response of'Elepaio individuals despite the existence of differences in the acoustic traits between both populations.—Oñate-Casado, J., Sebastián-González, E. & Hart, P.J. (2020). Response of male Hawaii Elepaio Chasiempis sandwichensis to conspecific songs: a small-scale playback study. Ardeola, 67: 387-400.

The Canary Islands are characterised by an outstanding level of biodiversity with a high number of endemic taxa. The Canarian avifauna is no exception and six extant avian species are recognised as endemic. However, we have a limited understanding of the genetic structure of these taxa, which makes it difficult to identify conservation priorities based on the existence of unique lineages. we analysed the diversification process and demography of the Canary Islands Chiffchaff Phylloscopus canariensis using two mitochondrial genes (cytochrome b and cytochrome oxidase subunit I). Although the species colonised the Canary Islands during the early Pleistocene, our results suggest a recent process of differentiation, which ran in parallel to the Last Glacial Maximum. Chiffchaffs from Gran Canaria emerge as a unique lineage since none of the haplotypes found on this island were recorded anywhere else in the archipelago. Our findings suggest a process of divergence according to the gradual colonisation and subsequent isolation of nearby islands. Demographic results show a stable trend of Chiffchaff populations until the colonisation of Gran Canaria (ca. 15,000 years ago), where the species significantly increased its effective population size. Nowadays, the effective population size of the Canary Islands Chiffchaff is stable, which highlights the ability of Chiffchaffs to adapt to local disturbances related to human activities. Overall, our results provide a scenario of incipient differentiation of the Canary Islands Chiffchaff and, importantly, underscore once more the role of Gran Canaria in driving speciation processes in this archipelago.—Illera, J.C., Ramírez, A., Rodríguez, L., Polypathellis, K. & Pérez-Tris, J. (2020). Maternal genetic structure reveals an incipient differentiation in the Canary Islands Chiffchaff Phylloscopus canariensis. Ardeola, 67: 401-414.

The endangered Steppe Eagle Aquila nipalensis is a winter migrant to Pakistan but baseline data regarding its current distribution and population status there is sparse. The present study investigated new distributional records from the Poonch and Jhelum valleys of Azad Jammu and Kashmir, beyond the range of the current IUCN distribution map for Pakistan. It adds another 6,730km² to the known wintering range. Mixed wintering groups of adults and immatures, averaging 154 individuals annually, were counted in two survey years. Site counts averaged ten birds and ranged from 63 at Hajira, a waste dump, to just two, at Kalas. waste from slaughterhouses and other anthropogenic sources appeared to be the main food source since the largest eagle concentrations were at dump sites. we suggest that the addition of the study area to the wintering range map of the species and recommend annual monitoring of the population. —Bari, F., Rehman, E.U., Kabir, M. & Ahmad, S. (2020). An extension to the known wintering range of the Steppe Eagle Aquila nipalensis, in the Poonch and Jhelum Valleys, Azad Jammu and Kashmir, Pakistan. Ardeola, 67: XX-XX.

Bahía de Banderas in Jalisco, Mexico, contains important vegetation areas for the maintenance and nesting of Military Macaws Ara militaris. However, the forests of the region are not used randomly by Military Macaws across the landscape. This study aimed to evaluate differences in floristic composition, diversity and structure among forest patches used by the macaws for nesting/ roosting or for feeding, and at sites from which the macaws are absent. Field sampling was conducted in 16 plots of 1,000m² of tropical subdeciduous forest. Statistically significant differences were found in the floristic composition between patches used and avoided by Military Macaws. The used areas were approximately twice as diverse as the avoided areas. The forests at used sites presented a great abundance of species registered as part of their diet, in addition to non-food species such as Oxandra lanceolata, a tree that may be an important component of macaw habitat. In contrast, the dominant species in avoided areas are those associated with disturbed areas and do not provide food for Military Macaws. Our results indicate that Military Macaws select forest fragments in response to disturbance, using forest patches that offer suitable opportunities for nesting and feeding.—Flores-López, E., Montero-Castro, J.C., Monterrubio-Rico, T.C., Ibarra-Manríquez, G., López-Toledo, L. & Carlos Bonilla-Ruz, C. (2020). Differential use of forest patches by the Military Macaw Ara militaris (Psittacidae) in coastal tropical forests of Jalisco, Mexico. Ardeola, 67: 423-432.

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.

En este informe se muestra información sobre 149 especies que se reparten por toda la geografía nacional. Entre ellas, se incluyen 28 especies que aparecen de forma escasa para las que se muestra su distribución espacio-temporal en 2019 mediante mapas y gráficas (véase De Juana y Garcia, 2015; Gil-Velasco et al., 2018; Rouco et al., 2018). Para contabilizar el número de citas para cada especie escasa se revisaron las observaciones disponibles en diferentes plataformas de recogida de datos, especialmente en eBird (eBird, 2020; Observado, 2020; Reservoir Birds, 2020 y Ornitho, 2020), descartando aquellas que aparentemente correspondieran a las mismas citas hechas por diferentes observadores con el objeto de contar con muestras de datos lo suficientemente homogéneas. Para el archipiélago canario, se incorpora un buen número de citas correspondientes al episodio de calima que se produjo a finales de febrero de 2020. Dichas circunstancias meteorológicas provocaron la arribada de muchas aves accidentales procedentes del noroeste africano de las que dará cuenta el correspondiente informe del Comité de Rarezas de SEO/BirdLife, junto con muchas otras especies de paso que se pudieron observar en las islas con mayor frecuencia y en números más altos de lo habitual, y de las que se sintetiza en el presente informe aquellas observaciones más relevantes. Se sigue la secuencia taxonómica de acuerdo con la nueva lista patrón de las aves de España (Rouco et al., 2019).