Jose Enrique Martínez

Many studies have highlighted the potential negative effects of recreational hunting on wildlife species. In this study, we used a long-term (14 years) dataset to evaluate the effect of red-legged partridge Alectoris rufa call-lure hunting, a type of hunting that occurs from fixed places (hunters in blinds close to a live caged lure) in late winter, on the incubation behaviour and hatching success of Bonelli’s eagles Aquila fasciata in southeastern Spain. Call-lure hunting affected the incubation behaviour of Bonelli’s eagles, but this effect varied in relation to the distance between the hunter and the nest and whether a gunshot occurred during the hunting activity. Call-lure hunting only induced an eagle’s reaction behaviour leading to temporary interruption of incubation if close (< 600 m) to the nest. Our models showed that a combination of acoustic and visual stimuli caused a longer duration of the reaction, although the specific contribution of a gunshot was almost three times greater than that of a hunter´s presence alone. In territories where call-lure hunting occurred, we also found a positive relationship between hatching success and the altitudinal difference between the nest and a hunter´s blind; the probability of breeding failure increased with increasing nest exposure to hunting activity. Our results suggest that a buffer zone around Bonelli’s eagle nests of 600 m would eliminate all impact of these hunting activities on eagles, and that location of blinds should also be considered to minimize exposure of nests to hunting activity to reduce disturbances and potential reproductive failures. This behavioural study may contribute to a better understanding of the magnitude of the conflict and provides alternative solutions for reconciling conservation and hunting.

El 87% de las especies de buitres del mundo están en algún grado de amenaza, motivado fundamentalmente por el incremento de la mortalidad no natural, cambios en el uso del suelo y regulaciones de las actividades agro-ganaderas. La población ibérica del buitre leonado (Gyps fulvus) experimentó un notable incremento en el último medio siglo. En este trabajo examinamos los cambios en el tamaño poblacional y éxito reproductor (pollos/parejas que inician la reproducción) en el periodo 1985-2025 en Bizkaia. La especie estuvo prácticamente desaparecida a mediados del siglo XX (cinco parejas en 1979), recuperándose paulatinamente a partir de los años ochenta, hasta alcanzar un máximo en 2024 de 159 parejas en 27 colonias distribuidas en tres metacolonias (zonas separadas entre sí). Entre 2008 y 2025, detectamos un total de 290 nidos utilizados al menos en una ocasión, sumando 2.156 puestas de las que volaron 1.139 pollos (0,53 pollos/puesta). Las colonias pequeñas tenían pocos nidos que eran utilizados anualmente, mientras que las colonias grandes acumulaban nidos que eran utilizados sólo ocasionalmente, de forma que a medida que aumentaba el tamaño de la colonia, crecía el número de nidos disponibles no utilizados. La productividad no varió de forma significativa entre años. El crecimiento poblacional y el éxito reproductivo no fue parejo en las tres metacolonias, estando condicionados por la meteorología, que difería geográficamente y que determinaba el uso diferencial de los nidos de las colonias, y las variaciones en la disponibilidad de alimento.

We analysed the mechanisms that, together with Mendelian inheritance, may be acting in the maintenance and evolution of colour polymorphism in the Booted Eagle ( Hieraaetus pennatus ), using observational data from successful breeding events of mixed pairs formed by light morph males and dark morph females, from a long-term study conducted in south-eastern Spain. Our results show that dark offspring produced in breeding events involving mixed-morph pairs far exceed the value expected in the Hardy–Weinberg equilibrium. Two-eaglet broods mostly resulted in one fledgling of each colour morph and in broods in which only one survived, it was predominantly the dark morph, with a ratio of 0.143:1 light/dark. In the two-egg clutches where only one hatched, the resulting eaglet was mostly dark morph with a ratio of 0.167:1 light/dark. Furthermore, three single-egg clutches produced a dark morph eaglet fledgling. However, these biases in embryo viability, chick survival and single clutches accounted for only seven (19.44%) of the 36 dark eaglets obtained. Of the remaining twenty-nine, six (16.67%) were expected according to Hardy–Weinberg equilibrium and twenty-three (63.89%) were produced by disassortative mating, a phenomenon described in previous studies, whereby heterozygous light males preferentially mate with dark females, likely based on the imprint of the colour morph of their mother. This long-term monitoring of breeding events has allowed us to understand the importance of each of the combined phenomena that contributes to the positive bias towards the dark morph in relation to the expected proportion according to the Hardy–Weinberg equilibrium.

Moult, breeding, and migration are the three major life‐history events in the annual cycle of birds. All are energetically demanding processes that rarely overlap. In large raptors such as the Egyptian vulture Neophron percnopterus , completing a full moult may take more than one year, requiring birds to balance this process with other life‐cycle events. We analysed 740 moult cards from across the species' distribution, including migratory, sedentary and mixed subpopulations, to test predictions about trade‐offs between the physiological demands of migration and moult. Juveniles began moulting in January–February of their second calendar year and continued ‘year‐round' until their fifth calendar year. Adults, however, suspended moult from the months preceding spring migration until the late breeding phase. Subadults from the Canary Islands started moulting earlier and completed it faster than those from western Europe, while adults from western Europe initiated moult later than adults from the Canary Islands, India, and Oman. Sedentary subpopulations, particularly that from the Canary Islands, showed a greater moult extent and replaced more primaries annually than migratory and mixed subpopulations, whereas the wintering subpopulation of southwestern Spain (Extremadura) exhibited the smallest moult extent. Moult symmetry decreased from the second plumage onwards and differed between the Canary Islands and Oman subpopulations. Geographic differences in moulting patterns likely arise from population‐specific life‐history trade‐offs, reflecting local adaptations or responses to environmental constraints. These patterns highlight the influence of migratory strategy on moult progression and suggest that sedentary lifestyles may allow more extensive feather renewal in long‐lived raptors.

El alimoche común (Neophron percnopterus) es una de las especies de buitres globalmente amenazadas y con una tendencia poblacional decreciente. En el año 2015 se aprobó el Plan Conjunto de Gestión de las Aves Necrófagas de Interés Comunitario de la Comunidad Autónoma del País Vasco (CAPV) en respuesta a la necesidad de protección de estas especies. Durante 26 años (2000-2025), realizamos el seguimiento de la población reproductora de Bizkaia. En total localizamos 98 nidos diferentes correspondientes a 24 territorios, en los que contabilizamos 418 puestas. La productividad media anual (± desviación típica) fue de 0,56 ± 0,17 pollos por pareja controlada, 0,72 ± 0,18 pollos por pareja reproductora y 1,20 ± 0,17 pollos por pareja con éxito. Cada territorio de alimoche contó con 4,08 ± 1,67 nidos, utilizándose cada uno de ellos 4,00 ± 4,48 ocasiones/años. El periodo máximo detectado, transcurrido entre dos usos del mismo nido, fue de 16 años. Cada nido tiene asociados dormideros y posaderos habituales de la pareja, que forman la superficie de las Áreas Críticas de los Alimoches (ACAs). A partir de estas ACAs, siguiendo el Plan Conjunto de Gestión, se aplican buffers de 250 m, 1000 m o 10 km de radio con los que se gestionan las actividades que pueden suponer un riesgo para la especie. La implementación progresiva y acelerada de proyectos eólicos y sus infraestructuras eléctricas asociadas supone un importante riesgo para la conservación de esta especie. Resulta fundamental aplicar el conocimiento de la ecología espacial de la especie para ordenar el territorio de forma sostenible.

Survival is a life history trait that contributes most to population dynamics in long‐lived birds, and the study of individual characteristics is relevant for population conservation. Here we provide information on territorial recruitment and individual replacement in a population of Bonelli's eagle Aquila fasciata in southeastern Spain based on a long‐term photographic capture–recapture 19‐year dataset. We also investigated how individual factors such as sex, age, experience and age at first breeding influence the apparent survival of breeding Bonelli's eagles using Cormack–Jolly–Seber models. An increase in recruitment rates and a decrease in age at first breeding were observed in the breeding population over time. The apparent survival was high and the reproductive dispersal was very low. The improvement in apparent survival was age‐related and higher in females (0.90 for non‐adults and 0.92 for adults) than males (0.87 for non‐adults and 0.89 for adults). These findings can be explained by age‐related improvements and differences in movement behaviour between sexes during the breeding season, with females being exposed to lower risks from anthropogenic or natural causes. We also found a positive relationship between territorial experience and the probability of apparent survival, with inexperienced female breeding birds having a higher survival than males. Our results showed that immature breeders had a similar survival to experienced or older birds breeding for the first time, suggesting that age at first reproduction is controlled by reproductive restraint. Our results provide demographic information that improves the understanding of the population dynamics of the long‐lived territorial species, and their estimation has important implications for the management and conservation of Bonelli's eagle populations.

There has been increasing recognition of the adverse effects of outdoor recreation on the behavioural ecology, breeding success and ultimate abandonment of territories in several raptor species, such as the Bonelli's Eagle (Aquila fasciata). We assessed the effects of human activities on the behaviour and breeding success of Bonelli's eagles breeding in south‐eastern Spain, using a 14‐year long‐term data set. Our results showed a weak behavioural response to human activities. The probability of eagle reaction varied among the human activities assessed and increased when they occurred close to a nest, being most marked for ecotourism activities. In general, the probability of a bird reacting increased sharply when an activity occurred closer than 480 m from the nest, but reactions were negligible when an activity occurred 1000 m away. Ecotourists only affected Bonelli's eagle behaviour at distances <300 m from the nest. We found a negative relationship between human activity and Bonelli's eagle behaviour: the probability of a reaction decreased with the increasing frequency of human activities, suggesting a degree of eagle habituation. Breeding success did not vary with a pair's experience of disturbance, nor between the periods before, during and after the COVID‐19 lockdown but did increase with the frequency of human activities. Our results indicated that Bonelli's eagles can develop a degree of tolerance to human activities during the nesting season. This behavioural plasticity offers the opportunity to harmonize anthropogenic activities with the application of specific conservation measures for this species in humanized landscapes. Our findings led to suggestions to minimize the detrimental effects of human activities and to optimize the conservation management of Bonelli's eagles in Southeastern Spain. More generally, our study emphasises the value of behavioural ecology studies for guiding conservation. Read the free Plain Language Summary for this article on the Journal blog.

As land-use cover types affect wintering birds’ strategies, studying their habitat suitability for species conservation is relevant. Predictive spatial models are considered excellent tools for conservation planning and improving our understanding of species distribution. Here we build models to predict the spatial distribution of raptor species that overwinter in SE Spain. We modelled the wintering raptor species distribution based on the presence-only data obtained between 2017 and 2019 and analysed their habitat preferences based on elevation and land-use cover variables. Our results show that altitude and distance to the coastline are the most important environmental factors to affect most species’ habitat suitability. Habitat type-related factors are other important predictors, and raptors subject of this study prefer lowlands and areas close to the coastline for overwintering by selecting open habitats, which include wetlands and irrigated and rainfed crops. This study highlights the importance of the habitat heterogeneity generated by wetlands and herbaceous crops within a low-altitude range as the optimal environment for wintering raptors. Such information should be considered for raptor conservation planning in human-altered landscapes.

Although once considered uncommon, there is growing evidence of widespread senescence in wildlife populations. However, few studies have examined the traits involved, inter-sexual differences, and environmental correlates of age-specific performance in raptors. We studied age-specific reproductive performance and actuarial senescence (decrease in survival probability with age) in a peregrine falcon population monitored for 21 years. We analysed changes with age in the number of offspring produced and incubation start date. We also inspected variation in lifespan and breeding lifespan (number of breeding occasions in a lifetime). In every case, we assessed associations between variations in traits and age, sex, recruitment age, and environmental conditions (cumulative rainfall during breeding season) experienced upon the first breeding attempt. We found scarce evidence for reproductive senescence. Only the incubation start date in females, which was delayed after approximately 8 cy (calendar years), suggested reproductive senescence in our study population. Regarding actuarial senescence, our data did not support it as we only found evidence of higher juvenile mortality. Furthermore, expected lifespan in peregrines recruited at 2 cy was associated with conditions experienced upon the first breeding attempt. The lifespan and breeding career of individuals recruited as yearlings and experiencing low rainfall upon first breeding did not significantly differ from those recruited as adults. However, those recruited as yearlings and experiencing poor environmental conditions upon the first breeding attempt showed reduced lifespan and breeding lifespan.

In bi-parentally built nests, there is evidence to suggest that nests are extended phenotypic signals that accurately indicate the quality of the building parent/s. Raptors often use a variety of materials to build their nests (natural, such as branches, but also non-natural objects), presumably due to their insulating properties, their suitability to advertise occupancy of the nest, and to decrease pathogen and parasite loads. However, in raptors where both sexes collaborate in nest construction, it is unclear whether nest building (taking the amount of material carried to the nest as the potential predictor) is an indicator of parental quality, and whether the effort expended by both sexes could constitute an honest signal of parental quality to their partners. Between 2011 and 2016, we monitored 16 nests of Bonelli’s Eagles (Aquila fasciata), and we examined data on sex, type of material brought to the nest, breeding experience, nest quality, timing, and nest-building investment prior to egg-laying from 32 identifiable Bonelli’s Eagles during the pre-laying period to investigate the relative contribution of the sexes to the amount of nest material gathered. Our results indicate that sex is not a determining factor in nest-building effort, and that females did not increase their parental effort in response to the male’s contribution, and supply of materials did not increase during the pre-laying period. In contrast, our models showed that: (1) the type of material supplied to the nest by both sexes varied significantly throughout the pre-laying period and (2) nest-building effort was determined by individual experience and nest quality. Therefore, our study suggests that male nest-building behaviour and investment by Bonelli’s Eagles cannot be considered as an extended phenotypic signal. The differential use of hard and green material by both sexes in the early and late stages of nest-building period, and the fact that the more experienced individuals contributed a larger amount of material on low quality nests, are discussed in the contexts of signaling nest occupancy to conspecifics and competitors and the decrease of ectoparasite loads during the pre-laying period.