Philornis flies exert strong negative selection on avian host life histories. However, their possible influence at the southern limits of parasite distribution remains poorly studied. We collected data on Philornis parasitism (prevalence, parasite load and latency) during three consecutive breeding seasons of the Masked Gnatcatcher Polioptila dumicola, Vermilion Flycatcher Pyrocephalus rubinus and Blue-and-yellow Tanager Pipraeidea bonariensis in a south temperate forest in Argentina. We hypothesised that Philornis parasitism would negatively influence both the growth and survival of infected nestlings. Regarding body size differences among nestlings of these three host species, we predicted that nestling survival in parasitised nests and parasite load per nestling would be greater the larger the species, and that the number of growth parameters that differ between parasitised and non-parasitised nestlings would be greater the smaller the species. We monitored 564 nests and found prevalence to be 16.7% for the Masked Gnatcatcher, 30.1% for the Vermilion Flycatcher, and 37.9% for the Blue-and-yellow Tanager. Parasitism increased during the season for all three species. As predicted, for the three species, nestling survival was lower in parasitised nests (∼30%) than in non-parasitised nests (∼90%) and for each species, one or more growth parameters were significantly lower for parasitised nestlings compared to non-parasitised nestlings. Our prediction relating to host body size was partially supported since differences in parasite load only emerged in nests that produced fledglings, as well as in the extent of growth parameters affected. This is the first study providing detailed data of Philornis fly parasitism and how this parasite affects the fitness of three bird hosts at the southern limit of the parasite's distribution.—Gonzalez, E., Jauregui, A. & Segura, L.N. (2022). The impacts of parasitic flies (Philornis spp.) on nestlings of three passerines in a southern temperate forest of Argentina. Ardeola, 69: 3-20.

Individual flexibility in breeding time is essential to respond to unpredictable changes in environmental conditions. Repeatability quantifies the consistency of the expression of phenotypes over time due to differences between individuals. Here, we estimate the repeatability of breeding date (laying date of first egg), hatching date and timing of pre-breeding events in a population of Pied Flycatchers Ficedula hypoleuca monitored over three decades in central Spain. We found low repeatabilities of breeding and hatching dates (respectively, R = 0.135 and R = 0) and among-year fluctuations (R = 0.276 and R = 0.218) in the expression of these traits. Repeatabilities of mating dates and of the interval between mating and egg laying were also very low (respectively R = 0.053 and R = 0) and among years (respectively R = 0.218 and R = 0.172), suggesting that Pied Flycatcher females are flexible to adjust their breeding schedule to current breeding conditions. We interpret the low consistency of traits related to breeding phenology as strong support for female phenotypic plasticity in breeding timing and the potential of such traits to respond to changing environmental conditions.—Le Vaillant, J., Potti, J., Camacho, C., Canal, D. & Martínez-Padilla, J. (2022). Low repeatability of breeding events reflects flexibility in reproductive timing in the Pied Flycatcher Ficedula hypoleuca in Spain. Ardeola, 69: 21-39.

Mountains support high biodiversity, often including endemic and vulnerable species, but they are also particularly sensitive to climate change. Whilst studies on mountain biodiversity at the species level are common, studies that consider whole assemblages are scarce. We assessed how an alpine bird assemblage varied in terms of ecological habitat niche by surveying birds and habitat at point count sites placed along elevational gradients (1,700-3,000m) in the Western Italian Alps. Niche breadth, as measured by habitat use, increased along the gradient, suggesting that being more generalist is an advantage in terms of survival at high elevation. Niche position also increased with elevation, which means that species occurring at higher elevations use habitats that are atypical with respect to the average species in the assemblage. Both niche breadth and position were negatively associated with habitat diversity, but these relationships were mainly driven by species occurring at elevations above 2,500m, suggesting that high alpine specialists show a different pattern from the other species of the assemblage. Our results therefore generally supported the idea that a wider niche breadth is useful in harsh environments, such as high mountains, enabling the exploitation of a wider range of resources. The broader niche of many high elevation species may therefore indicate some degree of resilience to environmental change, as long as key habitat types are maintained.—Mermillon, C., Jähnig, S., Sander, M.M., Alba, R., Rosselli, D. & Chamberlain, D. (2022). Variations in niche breadth and position of alpine birds along elevation gradients in the European Alps.

The Red-billed Chough, a species of conservation priority in Europe, is threatened by habitat encroachment, decline of pastoralism, heavy use of pesticides and disturbance by recreational activities. Its future greatly depends on the quality of its remaining habitat, particularly in mountains where no previous study has explored the effects of climate and snow condition on its populations. In the Gavarnie special protection area (9,300ha, Pyrenees National Park), a highly mountainous open landscape mainly covered by grassland, alpine moorland, screes and rocks, we compared the reproductive success of Red-billed Choughs during two very contrasted years, 2013 and 2014, in terms of snow phenology in spring. We also evaluated foraging habitat selection during the young rearing period. Habitat selection was estimated by modelling the probability, for 50 × 50 m² spatial units sampled in the study area, of being observed to be used by choughs for foraging. Breeding success was much lower during the year with prolonged spring snow cover, especially at higher elevation: 11 breeding pairs were present, compared to 22 pairs during the following year when snow cover phenology was more typical. Nesting phenology was delayed by ten days in the year with prolonged snow cover. Variables that positively influenced the probability for choughs to use spatial units as feeding areas were mostly linked with the presence of low vegetation (herbaceous or mixed scrub and grassland areas, grazed areas), and the absence of snow (time of snow cover during study period, exposure to solar radiation, presence of wetlands). We suggest that snow cover at the end of the cold season can create a spatial mismatch between customary chough nest locations at high elevations and areas suitable for foraging. The consequence is a scarcity of nesting attempts and low breeding success in the mountainous areas during years with prolonged and high altitude snow cover in spring. We also use these results to suggest the potential for this species to be used as an indicator for the effects of changes in climate and pasture grazing practices.—Fontanilles, P., Boulicot, I. & Chiffard-Carricaburu, J. (2022). Negative effects of snow cover on foraging habitat selection and breeding success in the Red-billed Chough Pyrrhocorax pyrrhocorax. Ardeola, 69: 59-74.

Ecological responses of nocturnal predatory birds to forest cover and other geospatial predictors vary both geographically and taxonomically. Considerable knowledge gaps exist regarding the habitat associations of the Sri Lanka Frogmouth, a nocturnal bird restricted to Sri Lanka and the Indian Western Ghats. Via a 20-year island-wide survey, we searched for frogmouths in Sri Lanka to determine their habitat associations at both local and landscape scales and developed a habitat suitability model (HSM) to predict both current and future distribution. We confirmed frogmouth presence in 18% of the surveyed sites across all major bioclimatic zones (wet, intermediate, dry, and arid) from lower elevations (11-767m), comprising a broad geographic range. Frogmouth presence was mostly limited to forests (90%) with a few sites in agricultural mosaics. Land protection, altitude and both local and landscape-scale forest cover, as well as forest-cover loss at both spatial scales, were strong predictors of frogmouth presence. According to our HSM, the southwestern lowlands and parts of the intermediate zone contained the most suitable areas for frogmouths despite their smaller extent. Although the dry and intermediate zones contained extensive habitats for frogmouth, these regions were relatively less suitable. The habitat associations and geographic range of this species in Sri Lanka differ from that seen in India through negative associations with altitude and absence from montane zones, absence from degraded or severely disturbed habitats and independence from proximity to waterways. The Sri Lanka Frogmouth is sensitive to anthropogenic disturbances, including historical forest losses. We recommend landscape-scale conservation planning that incorporates both primary and mature persistent secondary forests to ensure the protection of this unique iconic species.—Karunarathna, S., Dayananda, S.K., Gabadage, D., Botejue, M., Madawala, M., Peabotuwage, I., Madurapperuma, B.D., Ranagalage, M., Udayakumara, A. & Surasinghe, T.D. (2022). Distribution, habitat associations and conservation status of the Sri Lanka Frogmouth Batrachostomus moniliger. Ardeola, 69: 75-95.

Citizen science has become a powerful tool for collecting big data on biodiversity. However, concerns have been raised about potential biases in these new datasets. We aimed to test whether citizen science bird databases have more biases than professional scientific databases. Our hypotheses were 1) citizen science databases will have more data on “easy to spot” species, that are widely distributed and have large body sizes; whereas 2) professional databases will have more endangered species and species of special interest for research. We analysed six Spanish bird databases: three professional, two citizen science and one mixed database. Our results show that, in general, occurrences in citizen science databases are better explained by the studied variables than professional databases, but no clear differences were found when analysed individually. Both citizen science and professional databases contain invaluable information on biodiversity but every database comes with a particular history and its stored data is the result of years of field sampling with heterogeneous goals, sampling methods and sampling effort. Consequently, raw observations should not be used directly as an ideal survey of the distribution or abundance of birds. We need to uncover these biases and develop new methods to properly incorporate the extensive and heterogeneous biodiversity data that is readily available to research.—Galván, S., Barrientos, R. & Varela, S. (2022). No bird database is perfect: citizen science and professional datasets contain different and complementary biodiversity information. Ardeola, 69: 97-114.

Procellariiformes are one of the most threatened groups of birds of the world so knowledge of nesting habitat and factors affecting breeding rates are vital issues for their conservation. Although Cory's Shearwater Calonectris borealis is a well-studied seabird species on the whole, information on the relationship between its breeding parameters and nest site characteristics is quite limited. To address this gap, during 2017-2019, we conducted a study on its breeding performance on Tenerife, the largest and the most densely populated island of the Canarian archipelago. We constructed generalized linear mixed models to evaluate the potential effects of nest features on breeding performance. Two variables explained breeding success: the distance from the nest to the nearest paved road, and the presence of pebbles at the entrance of the nest-burrow, which correlated negatively and positively with breeding success, respectively. The majority of failures occurred during the incubation period. Breeding failures were mainly related to egg abandonment and rat predation upon eggs or chicks. Effective measures mitigating human-instigated disturbance (e.g. control of dogs, rats and feral cat populations, and reducing light pollution), together with studies on factors affecting demographic parameters, are needed to guarantee the long-term conservation of Cory's Shearwater and other seabird species on the main Canary Islands.—Rodríguez, B., Siverio, F., Acosta, Y. & Rodríguez, A. (2022). Breeding success of Cory's Shearwater in relation to nest characteristics and predation by alien mammals. Ardeola, 69: 115-128.

Little is known about the migration and wintering distribution of Eurasian Scops Owls Otus scops. We deployed GPS-loggers on breeding Scops Owls from a southern Spanish population to analyse migratory routes and migration timing of this trans-Saharan migrant. Tag deployment had no short- or long-term effects on Scops Owls. Individuals followed rapid autumn and spring migrations along the coasts of Morocco and Western Sahara and the western edge of the Sahara desert. South Spanish breeding Scops Owls wintered across a large area of West Africa; within Mauritania, Senegal, Mali, Gambia, Guinea and Sierra Leone, where they stayed apart from one another for 4-5 months. Wintering sites were primarily in tree-covered habitats suggesting that these are important for Scops Owl conservation year-round.—Avilés, J.M., Rodríguez-Ruiz, J., Cruz-Miralles, Á., Abad-Gómez, J.M. & Parejo, D. (2022). Migratory pathways, stopover locations and wintering grounds of southern Spanish Eurasian Scops Owls Otus scops. Ardeola, 69: 129-139.

La Sección Bibliográfica de Ardeola publica reseñas de libros publicados recientemente. 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.

This section includes the abstracts of some of the PhD-Dissertations submitted in Spain during the 2020-2021 academic year as well as some others not published in earlier volumes of Ardeola. They are in alphabetical order by University where they were presented and, then, by year and alphabetical order of the author's surname. This section also includes a link to access the full version of the reviewed thesis when available.