Aranzadi Science Society

We compile the information available for Spanish Sparrow (Passer hispaniolensis) in the provinces of Navarra and Huesca (northern Spain) until 2022 and add the results of specific censuses carried out in the spring of 2023. It is confirmed that the presence of this species in the area was practically anecdotal, with only 5 records in the last 20 years, and that in 2023 there was a sudden expansion towards the north, with more than 120 records recorded in the area, nesting proven in 17 points and detection of a communal roost far from all of them and probably linked to another colony of unknown location. 82.35% of the colonies were located a few meters from a raptor (Milvus milvus, M. migrans, Aquila chrysaetos and Accipiter gentilis)(11 colonies) or White Stork (Ciconia ciconia)(3 colonies) nest and in all cases there was also House Sparrows (Passer domesticus). The average size of each colony was 3.24 pairs (min-max 1–14) and the nests were at an average height of 11.18 m (min-max 6–18 m) and always in a trees (Pinus halepensis, Populus sp. and Sequoia sempervirens). The role of this species as indicator of climate change is discussed.

Above all, bird ringing must be safe for birds, for ethical reasons but also to ensure that data collection is not biased by marking effects. Bird ringing schemes are responsible for determining the size of the rings used to mark birds individually. This paper critically reviews the recommended ring sizes in the Aranzadi Ringing Scheme and proposes an objective criterion for ringers. A morphological analysis of tarsus width (MTW) and the width of the tibia–tarsus articulation (MAW), over a sample of more than 4000 individuals of 74 species of both passerines and non-passerines captured in Spain, revealed that the mean difference between the internal diameter of the recommended ring (IDR) and MTW was 32% in relation to MTW (sd 15.8%, 95% confidence interval 28–35%). Experience demonstrates that this clearance is adequate, but recommendations for rings with clearances either too narrow (<6%) or too wide (>50–60%) should be reviewed and changed, if possible, to bring them closer to a 32% standard.

El Cierro Cave (Ribadesella, Asturias, Spain) possesses one of the most complete Upper Palaeolithic stratigraphic sequences in northern Spain. Magdalenian occupations, particularly the lower Magdalenian, are well represented in its full sequence. This article presents the zooarchaeological analysis of the levels Cierro G1, Cierro G and Cierro F, dated by ¹⁴C to between 20,000 and 17,000 cal BP. The remains correspond to vertebrates (mainly large mammals and to a lesser extent fish and birds) and invertebrates (almost exclusively marine molluscs). The taphonomic analysis of the bones and shells has determined the role that the different animal resources played in the diet of the Magdalenian hunter-gatherers at El Cierro. The results obtained in each level of the sequence are compared and included in their regional context. This study also considers the way in which the Magdalenian groups at El Cierro processed the meat and fat of the different animal species and establishes the operational chain in the strategies of procurement, preparation and consumption of the prey.

The food available in open-air landfills, one of the most common predictable anthropogenic food subsidies (PAFS), can have a profound impact on animal biodiversity. Understanding how and to what extent PAFS affect wildlife is crucial for a sustainable management of resources. Most large gulls behave as opportunistic foragers and constitute a good avian model to analyze the effect of PAFS reduction on animal populations. Using individual data from a yellow-legged gull population of the Basque coast (northern Iberia) collected over a 15-year period, we estimated survival and reproductive parameters and used them to parameterize an age-structured population model to explore the effects of the local landfill closure. Local survival probability declined with time as a consequence of the progressive closure of the local landfill sites. The top-ranked models included a quadratic function of time, suggesting an acceleration of mortality during the later years, especially in juveniles, while survival in adults was linear. An effect more pronounced in first year birds than in older birds. Population models predict a decrease of the population and confirmed a greater sensitivity of the population growth rate to adult survival probability. Overall, our results suggest that the reduced carrying capacity of the system resulted after landfill closures have caused a population decline which is expected to continue in the near future.

We analyzed changes in the composition of the community of birds of prey and corvids in a rainfed agrosystem after the transformation of 37.2 % of the sampled area into irrigated land between 2005 and 2020. We sampled 57 transects (372 km per year) and fitted generalized linear mixed models (GLMM) to study changes in species occurrence. Our results showed that specific richness and the Shannon index did not vary significantly between rainfed and irrigated transects, but there was a certain positive trend when comparing the years 2005 and 2020. Regarding the differences detected for each species, the occurrence of Montagu’s harrier Circus pygargus, hen harrier Circus cyaneus, Eurasian short-toed eagle Circaetus gallicus, griffon vulture Gyps fulvus and carrion crow Corvus corone was significantly lower in irrigated land than in rainfed land, while magpie Pica pica, Western marsh harrier Circus aeruginosus, common kestrel Falco tinnunculus and black kite Milvus migrans showed a significantly higher occurrence in the irrigated transects. In addition, our findings confirm a significant decrease in occurrence between 2005 and 2020 both in rainfed and irrigated areas for Montagu’s harrier, hen harrier and magpie, while Western marsh harrier, golden eagle Aquila chrysaetos, common buzzard Buteo buteo, red kite Milvus milvus, griffon vulture Gyps fulvus, red-billed chough Pyrrhocorax pyrrhocorax and Western jackdaw Coloeus monedula were detected significantly more frequently in 2020 than in 2005. These results suggest that assessment of the impact of a new irrigation system should focus on the most characteristic species of rainfed agrosystems because the apparently positive effect on other species, equally protected but more generalist, may mask the real effect on conservation.

Background: DNA barcoding allows for species identification and description of genetic diversity. However, in the Middle East, information on genetic diversity is accumulating at a slower pace compared to that of other regions. Methods: The COI sequence of 24 lizard and snake species in Qatar that represent major families within the order Squamata were sampled and amplified via PCR using RepCOI primers (apart from one species). Purified amplicons were then aligned, and high-quality sequences were uploaded to BOLD. Using Sphenodon punctatus as the outgroup, the phylogenetic analysis was conducted using raxmlGUI software following the maximum likelihood method. Results: The COI sequence from each of the species was obtained and the consensus sequences were submitted to GenBank. In the phylogenetic analysis, a close relationship between members of the Agamidae and Serpentes was confirmed. While members of the same genus often showed sister-taxa relationships, and species in the same family were clustered with reasonably high bootstrap supports, the COI-based phylogeny was not able to resolve the relationships among genera within the families or identify relationships with high resolution at deeper lineages. Conclusion: Although ideal for species identification, COI gene sequencing is limited in phylogenetic inference due to high mutation rates that restrict its effectiveness for resolving relationships at deep phylogenetic levels. However, COI gene sequencing can be combined with nuclear markers for a more in-depth analysis.

The dynamics of migratory populations at wintering quarters can inform on population state and size because these areas act as demographic funnels, assembling birds from different origins. Previous evidence on survival probability of woodcock Scolopax rusticola wintering in northern Spain suggested a high harvesting pressure, but whether this pressure is causing a decline of woodcock occurrence at wintering quarters is still to be assessed. We used data from 3411 surveys conducted during the winter at 434 selected grasslands in the Gipuzkoa region, Northern Spain, to investigate the dynamics of woodcock occurrence probability, conditional on detection, over a period of 10 years (2009–2019). A 47% of the variation in woodcock occurrence within and across winters was explained by the monthly average minimum temperature. The remaining variation was due to a marked increase during the winters 2016 and 2017, contrary to the progressively decreasing values detected in previous years. At present, these abrupt yearly fluctuations prevent clear predictions on woodcock presence in the Gipuzkoa region. Future studies should explore woodcock occurrence probability according to scenarios of climate and habitat changes.

Variability in morphology and body size between populations of the same species is common and can be influenced by environmental conditions or differential migratory strategies. We focused on analysing body size differences between Yellow-legged gulls Larus michahellis from Medi-terranean and Cantabrian-Atlantic Iberian colonies as previous studies have suggested that Cantabrian-Atlantic gulls are smaller than Mediterranean gulls. However, those analyses were based on small sample sizes or did not account for sexual dimorphism. Here we analyse an extensive biometric data set (> 1,500 adult individuals), separating males and females, from nine different sites in each region. Our results reveal a 7% (median) difference both between regions and sexes, for most morphometric variables, with Mediterranean gulls having longer legs (tarsi) and heads (cranium-bill) and thicker bills (bill-depth). This interregional difference was even larger for body mass, Mediterranean gulls being 11% (males) and 20% (females) heavier than Cantabrian-Atlantic gulls. In particular, we found that individuals from the Mediterranean populations were allometrically longer-winged than their northern counterparts. We suggest, after discarding other factors, that this wing allometry may be related to

Several bird species benefit from anthropogenic food subsidies, such as landfills and fishing discards, that are being reduced owing to introduced legislation. For instance, since 2019, Europe has passed legislation to reduce dramatically the amount of fisheries discards through the Landing Obligation (LO), which states that all fish species under Total Allowable Catch (TAC) should not be discarded at sea. This European discard ban is expected to impact some gulls, as several gull populations have been observed to be heavily reliant on this resource. In this work, GPS tracking data from adult Yellowlegged Gulls Larus michahellis and Vessel Monitoring System (VMS) data (i.e. detailed data of the spatial distribution of fishing vessels) are used to determine the utilization of the marine habitat and the level of interaction of gulls with fishing activity offshore and discards in the south-eastern part of the Bay of Biscay. We found that these gulls had a low use of the marine habitat (ca. 15%) compared with terrestrial habitats, in contrast to the ca. 40% of the diet of this population which comprises marine prey. Furthermore, we detected that most of the gull tracking positions at sea did not interact with the fishing vessels (an overlap of 21.5% between gulls and VMS data). Conversely, other gull populations of the Iberian Peninsula were found to depend much more strongly on fishing activity. Therefore, the Yellow-legged Gull population of the SE Bay of Biscay did not obtain most of its fish prey from interactions with offshore fishing activity but most possibly by taking fish remains in harbours and by feeding themselves. Consequently, we expect a minimal effect of the European policies oriented to ban fishing discards offshore on this population, which would be more affected by policies directed towards the reduction of food availability in landfills or fish landing management in harbours.

Urban areas are constantly increasing, which can cause an effect in bird populations since human activities lead to nature alterations. Populations of House Sparrow (Passer domesticus) and Eurasian Tree Sparrow (Passer montanus) have been decreasing in Spain according to the latest national censuses in Spain. In this study, we tried to assess the population trend over more than two decades using ringing data from Spanish constant effort sites, as well as to determine the population and breeding success proxy in relation to habitat composition at landscape level. We analysed the data and confirmed the decreasing trend in the two species. However, Eurasian Tree Sparrow showed signs of increasing presence in urban areas. Furthermore, the productivity remained stable over sampling sites and years, meaning that the causes of the decreasing populations are affecting both adult and juvenile individuals.

Compared to other animal movements, prospecting by adult individuals for a future breeding site is commonly overlooked. Prospecting influences the decision of where to breed and has consequences on fitness and lifetime reproductive success. By analysing movements of 31 satellite-and GPS-tracked gull and tern populations belonging to 14 species in Europe and North America, we examined the occurrence and factors explaining prospecting by actively breeding birds. Prospecting in active breeders occurred in 85.7% of studied species, across 61.3% of sampled populations. Prospecting was more common in populations with frequent inter-annual changes of breeding sites and among females. These results contradict theoretical models which predict that prospecting is expected to evolve in relatively predictable and stable environments. More long-term tracking studies are needed to identify factors affecting patterns of prospecting in different environments and understand the consequences of prospecting on fitness at the individual and population level.

Artificial food subsidies like landfills generate very strong impacts on animal ecology and spatial behavior. Landfills indeed have been considered to be one of the most influential factors explaining the very fast recovery of many colonial waterbird populations worldwide, as documented for the white stork Ciconia ciconia. More recently, the increase of rice fields in some regions have also been argued to be part of an influencial process underlying the spatio-temporal distribution patterns of this species over many areas in southern Europe. It remains unknown whether these two habitat factors play an important role at explaining the spatial distribution pattern of the white stork and, more particularly, whether colony funding or colony size is dependent on them. Using data from a census conducted in 2018, we aimed to assess the effect of distance to a landfill or to rice fields, among other habitat factors, on the breeding colony size of a white stork population in northern Spain. Larger colonies were more likely to appear in trees or cliff, but less likely in buildings or other artificial substrates. They were also significantly more likely with decreasing distance to landfill, and when the habitat was dominated by dry cropland and meadows close to water bodies. Rice fields did not seem to have any significant effect. Our findings fit with those from other regions in Europe, and highlight the effect landfills have on population dynamics and spatial ecology for those species which are able to feed on this type of food subsidy. Our results also show that the main habitat cover over large geographic scales still plays a role independently of landfills. The European agricultural policies associated with the type and management of crops, and the Common Agricultural Policy in particular, will still have a decisive role for the species.

The Iberian Green Woodpecker is an endemic species of the Iberian Peninsula that has been little studied. We describe the nesting habitat selection of this species in the three biogeographic regions where the species is located. The characteristics of 78 trees with occupied nests and 312 other randomly chosen trees in the vicinity of the nests were compared, as well as the proportion of open and forest habitat in two buffers (100 and 1000 m) around the nest. Nesting was confirmed in 19 different species of trees, with a mean diameter at breast height of 41.10 cm (range 30–60 cm) and a mean height of 12.43 m (range 3–20 m). Differences were found between the three biogeographic regions regarding the use of open and forest habitats and the selection of the type of tree to nest. Even so, it can be concluded that this woodpecker prefers to nest in Populus and Fagus trees, dead or at least decaying, with the presence of fungi and with a DBH greater than that of the surrounding trees. These results show not only the great plasticity of this species, but also its dependence on the existence of decaying trees and of certain dimensions in which to build the nest.