José Luis Tellería
Grupo de Investigación Biología Evolutiva y de la Conservación
Evolution and Conservation Biology Research Group
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Figura: Distribución estacional de la abundancia según edades
Microdistribución del alcaudón dorsirrojo (Lanius collurio) y común (Lanius senator) en la Sierra de Guadarrama
Esteban Casaux y Jose Luis Tellería (en preparación)
En este estudio intentamos discriminar los factores determinantes de la micro-distribución de las dos especies de alcaudones en un área de simpatría. Investigamos especialmente el efecto de la humedad del suelo durante los secos meses del verano sobre la abundancia de insectos y la distribución de las dos especies.
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 (manuscript in preparation)
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.
Figure: Relationship between the total number of birds detected and the number of localities where they were recorded within the study area.
Loss of forest bird richness at the southwestern border of the Palaearctic
Roberto Carbonell. Ricardo Hernández-Lambraño, José Luis Tellería (in preparation)
We investigated the distribution of species richness and abundance of forest birds at the southwestern border of the Palaearctic (Morocco, Maghreb). Bird counts were conducted along transects in forests spanning a north-to-south gradient, and the potential effects of location and habitat suitability—measured in terms of forest cover, productivity, and habitat complexity—on species richness and abundance were analyzed. Results indicated that species richness and abundance decreased from north to south and were positively correlated with habitat suitability. Other factors, such as distance to the Atlas Mountains (a forested area) and shrub species richness, had less influence. Additionally, a nested pattern of species loss was observed within this geographical context, primarily associated with the geographical location of the sampled forests.
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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