José Luis Tellería

Grupo de Investigación Biología Evolutiva y de la Conservación

Evolution and Conservation Biology Research Group

Figura: Distribución estacional de la abundancia según edades

Does topographic humidity influence the distribution of the red-backed shrike (Lanius collurio, Linnaeus 1758) at its Mediterranean range limit? A comparison with the woodchat shrike (Lanius senator, Linnaeus 1758).

Esteban Casaux y Jose Luis Tellería (Ecologia Mediterranea, in press)

This study examines the factors influencing habitat selection by the red-backed shrike (Lanius collurio) in a mountainous region of central Spain, where it breeds sympatrically with the woodchat shrike (Lanius senator), a species better adapted to Mediterranean conditions. It investigates the role of soil moisture, a key constraint on primary productivity during the dry Mediterranean summer, which may influence arthropod abundance and, consequently, shrike distribution. The findings indicate that soil moisture is positively associated with prey availability but declines progressively as the summer drought intensifies. The red-backed shrike was observed to track these moist patches and to abandon the area as their extent diminished with increasing drought. In contrast, the woodchat shrike adapted its foraging behavior by shifting from moist to dry grass patches over the course of the summer. These results underscore the pivotal role of soil moisture in shaping the distribution of the red-backed shrike at the southern limit of its breeding range. Given that moist grassland is often maintained through small-scale irrigation associated with traditional agricultural practices, the findings highlight the species' dependence on such anthropogenic activities at the southern edge of its range.

An overview of the state of biodiversity in Spain: on the road to a National Red List programme

Jose Luis Tellería, Pablo García, ... Luis Santiago Cano Alonso (Oryx, under review)

The Spain Species Specialist Group (EsSSG) of the IUCN Species Survival Commission (SSC) was officially established in February 2024. Composed of around 150 specialists, it is organised into 18 taxonomic working groups. Among its aims is the assessment of the conservation status of Spanish species according to the IUCN Red List of Threatened Species (RLTS) categories and criteria. This study reviews the Master List of Spanish Species (60,653 species by 1 July 2025) and examines the taxonomic bias and low proportion of species included in the List of Species under a Special Protection Regime (LSSPR) and the RLTS (950), the main legal instruments for species protection in Spain. We found an overlap of 7.3% between LSSPR and globally threatened species in the RLTS. We also document considerable variation in the availability of specialists and information among taxonomic groups. Terrestrial vertebrates and butterflies are the best-known taxa, while other insects, spiders, harvestmen, molluscs, algae, mosses and liverworts are the least known. To overcome these shortfalls, we propose a monitoring plan focused on a broad taxonomic sample of species representative of different habitat types and biogeographic zones. The aim is to use the RLTS to monitor trends in the conservation status of biodiversity in Spain. This goal can only be achieved with support for training specialists in lesser-known taxonomic groups and the long-term commitment of the associations involved in this programme. Last but not least, this study could be a pilot experience for other SSC National Species Specialist Groups to set up their programmes and national red lists.

Figure: Changes in the daily flow of migrants in relation to wind patterns (A) and year (B), as well as variations in the total abundance of wintering birds across years (C).

Long-term Trends of Migratory and Wintering Passerines in the Strait of Gibraltar Based on Two Counts (1977 vs. 2024)
Alejandro Onrubia, José Luis Tellería (Ardeola 73 (2), 000-000)

This study examines changes in the migratory flow of six partially migratory passerine species (Alauda arvensis, Anthus pratensis, Motacilla alba, Carduelis carduelis, Fringilla coelebs, and Linaria cannabina) across the Strait of Gibraltar. Additionally, it evaluates whether these trends are associated with concurrent changes in the regional abundance of wintering individuals. To address these questions, the autumn migratory flow , recorded at the Tarifa Observatory (Spain) in 1977 and 2024, was compared with their abundance in January 1978 and 2025. The results reveal that all species experienced a decline in the number of individuals migrating southward across the Strait. However, only two species (Alauda arvensis and Anthus pratensis) exhibited a corresponding decrease in wintering abundance, while the remaining species showed no significant changes. The observed changes in migratory flow can be partially attributed to population trends documented by the Pan-European Common Bird Monitoring Scheme for four of the six species. These findings indicate that a reduction in migratory flow does not necessarily correspond to a decline in wintering abundance. They also underscore the influence of other regional factors in shaping winter bird abundance patterns.

Regional demographic processes override local drivers in bird responses to land abandonment in Juniper woodlands

Guillermo Fandos and José Luis Tellería (in prep.)

Predicting species responses to environmental change based solely on local-scale approaches may prove inadequate when the underlying ecological processes operate across broader spatial scales. In this study, we investigated long-term changes in bird communities inhabiting Spanish juniper woodlands undergoing shrub and tree encroachment, a widespread phenomenon in abandoned rural landscapes. Utilizing aerial imagery alongside standardized bird surveys conducted in 1980 and 2022 in Spain, we examined whether observed shifts in bird assemblages were primarily driven by local habitat transformations or more accurately explained by large-scale population trends. Our results revealed a significant increase in tree and shrub cover across all study sites. Concurrently, bird assemblages became increasingly dominated by forest-associated species, whereas species linked to open habitats and ecotones exhibited pronounced declines. However, trends in species abundance at the European scale provided a stronger explanatory framework than habitat preferences, suggesting that the observed changes are more closely aligned with large-scale population dynamics than with local habitat modifications. These findings indicate that habitat management at local scales may have limited capacity to shape bird community composition, as broader-scale processes can exert a dominant influence on ecological patterns. Furthermore, they highlight the need for conservation frameworks that explicitly incorporate multi-scale dynamics in order to more effectively understand and manage biodiversity change.

Figura: Porcentaje de amenazas por captura o recolección.

El acceso libre a datos exactos sobre la distribución espacial de las especies amenazadas en España: ¿es hora de avanzar?

José Luis Tellería (en preparación)

Las bases de datos geo-referenciados ofrecen una información inexacta para evitar la localización de los individuos pese a que la captura o recolección de ejemplares no es un problema para la mayor parte de las especies amenazadas. Pese a ello, se ha generalizado la ocultación de esta información sin considerar que el impacto de muchas otras amenazas (impacto de infraestructuras, modificación del hábitat, etc.) puede prevenirse mejor si se conoce la ubicación exacta de los organismos afectados. Parece lógico sugerir que la precaución en el uso de estos registros espaciales no sea la norma en el tratamiento del conjunto de las especies amenazadas

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