Home-Range Size and Space Use of Territorial Bonelli’s Eagles (Aquila fasciata) Tracked by High-Resolution GPS/GSM Telemetry

High-resolution GPS/GSM dataloggers provide spatial information of the highest quality, which outperform previous tracking methods, such as Argos telemetry or conventional VHF ground-tracking. As a result, this has improved our knowledge of home-range behavior and spatial ecology of many species, including large raptors. In this paper, we use high-resolution GPS/GSM dataloggers to assess the home-range size and the role of sex, season (breeding or non-breeding season), and breeding status (reproductive or non-reproductive individuals) on the space use of Bonelli’s eagle (Aquila fasciata). To this end, 51 territorial individuals (25 females and 26 males) were equipped with GPS/GSM transmitters and were tracked over 7 years (2015–2021) in eastern Spain. Overall, we recorded 4,791,080 fixes that were analyzed through kernel density methods (50%, 75%, and 95% fixed kernels). The average individual home-range size according to the 95%, 75%, and 50% kernels was 54.84 ± 20.78 km2, 24.30 ± 10.18 km2, and 11.17 ± 4.90 km2, respectively. Overall, the home-range size of individuals occupying the same territory was similar, mainly due to the cooperative hunting behavior exhibited by the species. We did not find interannual differences in the home-range size (95% fixed kernel) of the majority of individuals, showing a strong territorial fidelity of the breeding pairs. In general, females’ home-range size was slightly smaller than males’ size due to the decrease in activity in the breeding season as a result of laying, incubation, and chick attendance at nests. No seasonal variation in the 95% kernel was found, but it was found in the 75% and 50% kernels. In regard to the breeding status, higher home-range size was recorded in the non-reproductive individuals. Moreover, we found a low neighbor overlap among the territories (4.18% ± 3.06%), which evidences a high level of intraspecific competition in the Bonelli’s eagle. Finally, this study highlights the advantages of the use of accurate telemetry information to improve our understanding of the spatial ecology of the endangered Bonelli’s eagle, which ultimately will serve to better inform management actions for its conservation.This work was supported by Red Eléctrica de España, ACCIONA Eólica de Levante, LafargeHolcim and the Wildlife Service of the Valencian Community regional government (Conselleria d’Agricultura, Desenvolupament Rural, Emergència Climàtica i Transició Ecològica, Generalitat Valenciana, Spain)

A new view of territoriality in large eagles: the territory pre-exists regardless of their occupants

Knowledge of vertebrate territoriality and spatial use is a topic of great interest in the study of animal behaviour and conservation biology. Investigating the plasticity of territory boundaries, the shape of territories and how territories can be modified depending on their owners is important to deepen our knowledge of the behaviour of territorial species. We analysed the variation and tested the similarity of the distribution area of individuals from the same territory between 2015 and 2021, using data from 51 Bonelli's eagles (Aquila fasciata) from 22 different territories, tagged with GPS/GSM transmitters in eastern Spain. We calculated the percentage of overlap between the territories of the same individual in different years using the 95% kernel density estimator. We also analysed the changes in territory size and shape following the replacement of territory owners either by a single individual or by the whole pair. Our results show that territories retain the same shape and extent regardless of the occupying members, and that their boundaries change little over time. Identifying and maintaining large eagle territories, regardless of their owners, is therefore key to ensuring the long-term recovery of these threatened species.This work was supported by Red Electrica de España, Iberdrola Foundation, ACCIONA Eolica de Levante, LafargeHolcim and the Wildlife Service of the Valencian Community regional government (Generalitat Valenciana, Spain)

Striking Variability in the Post-Reproductive Movements of Spanish Red Kites (Milvus milvus): Three Strategies, Sex Differences, and Changes over Time

It was assumed that the Spanish breeding population of the red kite (Milvus milvus) was resident, hence their movements were restricted to their breeding area for their entire lifecycle. However, recent observations indicated that the post-reproductive strategies of the red kite in Spain are more diverse. We tagged 47 breeding adult red kites in Spain and analyzed their movements during the post-reproductive period (July–February). We found three strategies in the population: migration (10%), sedentarism (70%), and sedentarism with post-reproductive movements (20%), based on seasonality and other movement parameters. Sedentarism with post-reproductive movements was a very variable strategy that involved all-direction wandering movements far away from the nest (up to 589 km) after breeding season, and then a returned journey toward the starting point in time for the next breeding season. Our results also suggest that sedentarism with post-reproductive movements is much more common in females than males. Furthermore, 17% of the individuals changed their strategy over the years. This study highlights the great individual variability and plasticity of the red kite and allows for a better understanding of spatial ecology in opportunistic raptors

Comportamiento espacial y territorial del águila-azor perdicera Aquila fasciata y del águila real Aquila chrysaetos en el sudeste de España

El estudio del uso del espacio y la territorialidad nos ayuda a tener herramientas para la conservación de especies. El territorio se ha definido de diferentes formas a lo largo de los años, se puede describir como el área defendida, el área dominada o el área de uso exclusivo entre otros. La territorialidad ofrece un lugar eficiente para satisfacer las necesidades básicas de alimentación, seguridad y reproducción. Las variaciones en los territorios de los animales pueden ser debidas a diferentes factores, como puede ser la densidad de población, la cantidad y calidad de los alimentos, las características del hábitat o los individuos que los ocupan. Estas variaciones se pueden estudiar de diferentes maneras: (i) tamaño y forma (capítulos 1, 2, 3 y 4); (ii) cambios estacionales (capítulos 1, 2 y 4); (iii) cambios anuales (capítulos 1, 3 y 4); (iv) cambios individuales (capítulos 1 y 4); (v) cambios respecto al éxito reproductivo (capítulo 1); (vi) cambios frente a una perturbación externa (capítulos 1 y 3). En esta tesis se ha empleado una base de datos que lleva acumulando información satelital desde 2015. Cuenta con más de 100 millones de localizaciones pertenecientes a 72 individuos de dos especies, águila-azor perdicera (56) y águila real (16), todos ellos marcados con dispositivos GPS/GSM. Capítulo 1: Morollón, S., Urios, V., & López-López, P. (2022). Home-range size and space use of territorial Bonelli’s Eagles (Aquila fasciata) tracked by high resolution GPS/GSM telemetry. Diversity. 14(12), 1082. En este capítulo se investiga el uso del espacio del águila-azor perdicera a través del tamaño del área de distribución. Se analiza el papel del sexo, la temporada y el estado reproductivo. Estos análisis se han llevado a cabo a través de métodos de densidad de kernel. En general, el tamaño del área de distribución de los individuos que ocupaban el mismo territorio es similar, principalmente debido al comportamiento de caza cooperativo exhibido por las diferentes parejas. No hay diferencias interanuales en el tamaño del área de distribución de la mayoría de los individuos, mostrando una fuerte fidelidad territorial de las parejas reproductoras. Debido a la disminución de la actividad en la temporada de reproducción a causa de la puesta, la incubación y la asistencia de los pollos en los nidos, el tamaño del área de distribución de las hembras es ligeramente menor que el de los machos. Los individuos territoriales no reproductivos muestran áreas de distribución mayores. La superposición entre territorios vecinos es muy baja y se evidencia un alto nivel de competencia intraespecífica en el águila-azor perdicera. Capítulo 2: Morollón, S., Urios, V., & López-López, P. (2022). Fifteen days are enough to estimate home-range size in some long-lived resident eagles. Journal of Ornithology, 1-6. En este capítulo se estudia la cantidad de localizaciones necesarias para que dos especies territoriales, águila-azor perdicera y águila real, definan su área de distribución. Se muestra que el número de localizaciones es independiente de la estación. Este objetivo es clave para los estudios de ecología espacial ya que la obtención de un gran conjunto de datos de animales marcados se vuelve difícil en términos económicos y logísticos. La dificultad para capturar y manejar individuos, la presión de trabajar con especies carismáticas y/o en peligro de extinción, y las limitaciones en el presupuesto financiero, hacen que muchas veces sea difícil trabajar con una gran cantidad de individuos. Además, en algunos casos, los transmisores dejan de emitir unos días después del marcado por diferentes motivos, incluida la mortalidad natural y no natural. En este apartado se muestra que después de un cierto número de días los individuos definen su territorio y mantienen su extensión y fisionomía. Capítulo 3: Morollón, S., Pausas, J. G., Urios, V., & López-López, P. (2022). Wildfire response of GPS-tracked Bonelli’s eagles in eastern Spain. International Journal of Wildland Fire, 31(9), 901-908. En este capítulo se analiza por primera vez el comportamiento de un águila-azor perdicera frente a un incendio forestal, el cual quema la mayor parte del núcleo de su territorio, incluidas las zonas de roquedos donde se situaba el nido. Se observa un efecto negativo inmediato durante los primeros días del incendio forestal. El individuo se aleja en dirección contraria del área en llamas. Sin embargo, al cabo de unos días, el individuo recupera su comportamiento habitual. Durante los años consecutivos tiene el mismo área de distribución y se reproduce con normalidad. Esto podría ser el resultado de la adaptación de esta especie a los recurrentes incendios forestales en el área mediterránea. Capítulo 4: Morollón, S., López-López, P. & Urios, V. (en revisión). A new view of territoriality. Design of protected areas with its application. Ornithological Applications. En este capítulo se explora el conocimiento sobre territorialidad y uso del espacio del águila-azor perdicera. Se examina la plasticidad de los límites del territorio, la topografía y cómo se pueden modificar los territorios en función de sus ocupantes. Se analiza y se demuestra la similitud del área de distribución de individuos del mismo territorio, ya que sus límites no varían a lo largo del tiempo. Para ello se compara el porcentaje de superposición del área de distribución anual de los diferentes individuos que ocupan un territorio. Así́ mismo, los diferentes niveles de densidad de kernel y la excentricidad del territorio. Estas variables nos muestran que las diferentes áreas tienen la misma topografía y extensión. La invariabilidad se acentúa cuando, tras un reemplazo de uno o los dos individuos de la pareja se sigue manteniendo la topografía y extensión. Esto nos lleva a pensar que la identificación y conservación de los territorios de las grandes águilas, independientemente de sus habitantes y del estado de ocupación, es clave para asegurar la recuperación de las especies a largo plazo

Fifteen days are enough to estimate home-range size in some long-lived resident eagles

In this paper, we show how many fixes are enough to define the territory of two long-lived resident raptors marked by GPS transmitters. To this end, we analyzed high-resolution GPS data from 50 territorial Bonelli’s eagles (Aquila fasciata) and 9 territorial Golden eagles (Aquila chrysaetos) equipped with GPS/GSM dataloggers. Our results show that between 2200 and 2800 fixes are enough to define the territory. This is interesting for movement ecology works where long-term GPS data series are not available.This work was supported by Red Eléctrica de España, ACCIONA Eólica de Levante, Lafarge Holcim and the Wildlife Service of the Valencian Community regional government (Conselleria d'Agricultura, Desenvolupament Rural, Emergència Climàtica i Transició Ecològica, Generalitat Valenciana, Spain)

Wildfire response of GPS-tracked Bonelli’s eagles in eastern Spain

Background: Little is known about the interaction between predators and wildfires, in part because the large home range and scarcity of predators make their study difficult, and their response is strongly species-specific. Aims: In this paper, we study, for the first time, the effect of wildfire on the behaviour of Bonelli’s eagles (Aquila fasciata) simultaneously tracked by GPS/GSM dataloggers in four neighbouring territories. Methods: One territory was burnt in a wildfire and the other three were used for comparison. We computed the home-range area by comparing individual spatial and temporal behaviour before, during and after the fire event using kernel density estimators and movement parameters. Key results: Our results show an immediate negative effect during the first days of the wildfire for an individual inhabiting the burnt territory – the individual flew directly away from the burning area. However, after a few days, the individual recovered their usual behaviour. The three neighbouring pairs did not show significant differences in behavioural parameters before, during and after the wildfire. Conclusions and implications: Our results suggest that occasional wildfires do not affect the distribution and density of Bonelli’s eagles in the short or medium-term (two years after fire). This could be the result of adaptation by this species to the frequent and recurrent wildfires in the Mediterranean area.This work was supported by Red Eléctrica de España and Wildlife Service of the Valencian Community regional government (Conselleria d’Agricultura, Desenvolupament Rural, Emergència Climàtica i Transició Ecològica, Generalitat Valenciana, Spain). We also thank project FIROTIC (PGC2018-096569-B-I00, Spanish Government)

Migration patterns of breeding Hen Harriers Circus cyaneus in Spain

Capsule: Tracked Hen Harriers Circus cyaneus breeding in Spain winter either in the southern parts of the Iberian Peninsula or in Morocco, although migration timing and distances did not differ between birds using different wintering regions. Aims: To study, for the first time, the migratory patterns of Hen Harriers breeding in Spain. Methods: Eight breeding adult Hen Harriers were tagged in Spain with GPS/GSM transmitters between 2019 and 2022 to study autumn and spring migration between breeding areas in central or northern Spain, and wintering quarters in southern Spain and Morocco. Results: Males and females did not differ significantly in their patterns of migration (dates for start and end of migration, duration, daily distance, and total distance) in either migratory period. Individuals started the autumn migration between July and January, with the peak migration in mid-October. Spring migration took place from February to April and peaked in mid-March. Mean (± sd) distances travelled were: daily distance 168.99 ± 80.10 km/day and total distance 995.07 ± 402.90 km in autumn, and 141.74 ± 41.41 km/day and 1035.26 ± 593.51 km in spring. Two types of migration patterns were found: intra-peninsular migration and migration to Morocco. Migration dates and distances did not differ significantly between individuals with intra-peninsular migration strategies and those migrating to Morocco. Conclusion: These results are the first to describe the migratory behaviour of Spanish breeding Hen Harriers using satellite telemetry. Knowledge of migratory routes and behaviour are important for planning the conservation of speciesThis work was supported by Fundación Iberdrola España (MIGRA program of SEO/BirdLife) and Natural England

Lesser kestrels of the same colony do not overwinter together

Migratory connectivity describes the linkage between breeding and non-breeding sites, having major ecological implications in birds: one season influence the success of an individual or a population in the following season. Most studies on migratory connectivity have used large-scale approaches, often considering regional populations, but fine-scale studies are also necessary to understand colony connectivity. The lesser kestrel Falco naumanni, an insectivorous migratory raptor which form colonies during the breeding period, was considered to have strong connectivity based on regional populations. However, no small scale studies on migratory connectivity have been conducted. Therefore, we GPS-tracked 40 adult lesser kestrels from 15 different Spanish breeding colonies, estimating the overlap index between home ranges and the distance between their centroids. It was found that lesser kestrels from the same breeding colony placed their non-breeding areas at 347 ± 281 km (mean ± standard deviation) away from each other (range = 23-990), and their home ranges overlapped by 38.4 ± 23.6%. No differences between intra-colony and inter-colony metrics were found, which suggests that lesser kestrels from the same breeding cluster do not overwinter together, but they spread out and mixed independently of the colony belonging throughout the non-breeding range of the species. Ultimately, this study highlights the importance of performing connectivity studies using fine-scale approaches.Funding for lesser kestrels tagging was provided by Iberdrola España Foundation (MIGRA program of SEO/BirdLife), GREFA (supported by Ministerio para la Transición Ecológica y Reto Demográfico, Junta de Castilla-La Mancha and SEITT, s.a.), Córdoba Zoo, Alcalá de Henares Municipality, and Global Nature Foundation within the LIFE Project “Steppe Farming” (LIFE15417NAT/ES/000734). Lina Lopez-Ricaurte has received financial support through the “La Caixa” INPhINIT Fellowship Grant for Doctoral studies at Spanish Research Centres of Excellence, “La Caixa” Banking Foundation, Barcelona, Spain. In Andalucia tags were funded by “KESTRELS MOVE” project (ref: CGL2016 79249 P) (AEI/FEDER, UE). At the time of analyses and writing, this study was supported by projects MERCURIO (ref: PID2020-421115793GB) (AEI/FEDER,UE) and SUMHAL (European Regional Development Fund4 (ref: LIFEWATCH-2019-09-CSIC-13) (MICINN, POPE 2014-2020). Logistic and technical support was provided by ICTS-RBD

The variability of juvenile dispersal in an opportunistic raptor

The juvenile dispersal of raptors is a crucial stage that stretches from parental independence to the establishment of the first breeding area. Between 2012 and 2020, 44 juvenile red kites Milvus milvus from the Spanish breeding population were tagged using GPS telemetry to study their dispersal. Juveniles left the parental breeding area at the end of their first summer and performed wandering movements throughout the Iberian Peninsula, returning to the parental breeding area the following year, repeating the same pattern until they settled in their first breeding area. We analyzed the mean distance from the nest, the maximum reached distances, and the travelled distances (daily and hourly) during the first two years of dispersal and compared them. Despite the high individual variability, variables describing the dispersal movements of juveniles showed a decreasing trend during the second dispersal year: 80 % of individuals reached a shorter maximum distance in the second year, 70% decreased their mean distance to the nest, 65% decreased their hourly travelled distances, and 50% decreased their daily travelled distances. On the other hand, the Red Kites usually combined wandering movements with establishment of temporary settlement areas (TSA). The average duration of settlement in the TSAs was 75 ± 40 days (up to 182 days) and were located at 182 ± 168 km from the nest. In those areas, juveniles used 781.0 ± 1895.0 km 2 (KDE 95%). Some of the TSAs were used by several individuals, which suggests that these areas might be good targets for conservation in future management plans