Individual repeatability in timing and spatial flexibility of migration routes of trans-Saharan migratory raptors.

Satellite-tracking technology has allowed scientists to make a quantum leap in the field of migration ecology. Nowadays, the basic description of migratory routes of many species of birds has been reported. However, the investigation of bird migration at individual level (i.e. repeatability in migratory routes and timing) still remains seldom explored. Here, we investigated repeated migratory trips of a trans-Saharan endangered migratory raptor, the Egyptian Vulture Neophron percnopterus, tracked by GPS satellite telemetry. We compared between- and within-individual variation in migratory routes and timing in order to assess the degree of repeatability (or conversely, the flexibility) in migration. To this end, we analysed a dataset of 48 trips (23 springs and 25 autumns) recorded for six adult birds during 2007-2013. Our results showed consistent migration timing at the individual level, both in spring and autumn. Interestingly, there was a high degree of flexibility in the routes followed by the same individual in different years, probably due to variations in meteorological conditions. Contrary to expectations of a faster migration in spring than in autumn owing to a time-minimization strategy for breeding, birds spent less time in autumn migration (13 ± 2 days, range = 9-18 d) than in spring migration (19 ± 3 days, range = 13-26 d), which can be explained by differences in environmental conditions en route. Egyptian vultures showed a consistent clockwise loop migration through western Africa, following more easterly routes in autumn than in spring. Finally, our results provide supporting evidence of low phenotypic plasticity in timing of migration (i.e. strong endogenous control of migration) and high flexibility in routes

Population size, breeding performance and territory quality of Bonelli's Eagle Hieraaetus fasciatus in eastern Spain

Capsule. A five-year monitoring study is described of overall population stability and differential reproductive success in relation to habitat heterogeneity. Aims. To assess the effect of the altitude and orientation on laying date and breeding performance, and analyse the effect of territory quality as a likely factor that could be regulating the population. Methods. We monitored a population of 28–33 pairs, from 2002 to 2006, counting a total of 131 breeding attempts. Results. Territories located at lower altitude showed higher mean fecundity than those located at higher altitude. The mean laying date was February 18 ± 16 days. Laying date was positively correlated with nest altitude, the coastal pairs laying earlier than those in mountainous regions. Pairs located at lower altitudes showed higher mean fecundity than those located at higher altitudes. There was no preference in mean orientation either in breeding performance or in relationship to nest altitude. We did not find a difference in breeding performance between territories classed as being at high density and those classed as being at low density. Conclusion. The population has remained stable since the first national census was conducted 17 years ago. Our results could be explained in the light of the Habitat Heterogeneity Hypothesis. We suggest a differential reproductive success in relation to habitat heterogeneity.The Conselleria de Territori i Habitatge of the Generalitat Valenciana provided financial support to complete the monitoring of the 2005 breeding season (project N/REF. 28/BD/05)

A case of predation of an Eurasian Eagle Owl by a Bonelli's eagle.

Although some of these hypotheses are not mutually exclusive, in light of our field observations and experience with both species in the study area, we would favor the first hypothesis as food availability is low in our study area (P. López-López, C. García-Ripollés, J. Giménez, and V. Urios unpubl. data). The second and third hypotheses could also account for this behavior, especially considering previous events of nestling Bonelli's Eagles being killed by eagle-owls (Real and Manosa 1990). Notwithstanding, if the''predatorremoval hypothesis'' were true, the frequency of lethal interactions among both species would be probably much higher and thus previously reported in the literature. Unfortunately, we cannot rule out the fourth hypothesis, as the eagle-owl was partially consumed and hence we were unable to determine information about its body condition

Wind effects on the migration routes of trans-Saharan soaring raptors: geographical, seasonal and interspecific variation.

Wind is among the most important environmental factors shaping birds' migration patterns. Birds must deal with the displacement caused by crosswinds and their behavior can vary according to different factors such as flight mode, migratory season, experience, and distance to goal areas. Here we analyze the relationship between wind and migratory movements of three raptor species which migrate by soaring-gliding flight: Egyptian vulture Neophron percnopterus , booted eagle Aquila pennata , and short-toed snake eagle Circaetus gallicus . We analyzed daily migratory segments (i.e., the path joining consecutive roosting locations) using data recorded by GPS satellite telemetry. Daily movements of Egyptian vultures and booted eagles were significantly affected by tailwinds during both autumn and spring migrations. In contrast, daily movements of short-toed eagles were only significantly affected by tailwinds during autumn migration. The effect of crosswinds was significant in all cases. Interestingly, Egyptian vultures and booted eagles showed latitudinal differences in their behavior: both species compensated more frequently at the onset of autumn migration and, at the end of the season when reaching their wintering areas, the proportion of drift segments was higher. In contrast, there was a higher drift at the onset of spring migration and a higher compensation at the end. Our results highlight the effect of wind patterns on the migratory routes of soaring raptors, with different outcomes in relation to species, season, and latitude, ultimately shaping the loop migration patterns that current tracking techniques are showing to be widespread in many long distance migrants

Search Foraging Strategies of Migratory Raptors Under Different Environmental Conditions

Several studies have shown in different organisms how their movements can be fitted to different patterns to optimize search of food resources. According to abundance and availability of resources, different strategies will be optimal, such as Lévy and Brownian random search. We analyze the movement patterns of four species of migratory raptors with different degrees of ecological specialization in diet during the breeding and wintering periods to evaluate the differences according to species and season: the Egyptian Vulture, the Short-toed Snake Eagle, the Booted Eagle, and the Red Kite. From GPS locations, we obtained a set of segments and lengths that were analyzed to verify their fitting to the functions of Lévy and Brownian strategies. Egyptian Vulture’s trajectories fitted to both patterns during the breeding period, whereas during the wintering period most trajectories fitted a Brownian pattern. In the case of the Short-toed Eagle, fit was greater to a Lévy strategy throughout the year, while Booted Eagles and Red Kites exhibited a combination of search patterns. These differences could be accounted for different feeding strategies and environmental context over the annual cycle. In species with a specialized diet (i.e., Short-toed Eagle) the Lévy pattern would maximize the encounters with scarce and unpredictable resources, whereas for species with a broad trophic niche (i.e., Booted Eagle and Red Kite), movements could be adapted to exploit different resources according to their abundance. Scavengers like the Egyptian Vulture shift also between search strategies according to the distribution of carrion. Therefore, the analysis of food search patterns can be used as an indirect indicator to track changes in food availability across a broad range of environmental conditions. This is particularly important under the current context of global change which is largely expected to affect migratory species that spend their vital cycle in distant areas.Tracking of Booted Eagles and Red Kites has been made within the “Migra” program (www.migraciondeaves.org/en/) developed by SEO/BirdLife and financed by Fundación Iberdrola España. The Basque Government and the Biodiversity Foundation financed the tagging of several Red Kites in Spain. Tracking of Italian individuals was funded by Gallipoli Cognato Piccole Dolomiti Lucane Regional Park (Italy). Servicio de Vida Silvestre (Generalitat Valenciana) and different local governments funded part of the tagging. JV-M was supported by a FPU grant of Spanish Ministry of Education (reference FPU014/04671)

Interspecific Comparison of the Performance of Soaring Migrants in Relation to Morphology, Meteorological Conditions and Migration Strategies

Peer reviewe

European Journalism Observatory- a platform for training and professional networks in the Faculty of Information Sciences

The launching of a Spanish platform within the Observatory will serve as a training laboratory for undergraduate and graduate students of the Faculty of Information Sciences at the same time as for establishing a professional media network in and outside Spain. The European Journalism Observatory (EJO) is a network of 14 non-profit media research institutes in 11 countries where Spain continue to be the missing element. All researchers in the EJO network actively strive to transfer their knowledge to the media industry as well as interested publics outside the scientific community, as a platform to enable online availability of at least a portion of many publications in several languages

Diurnal timing of nonmigratory movement by birds: the importance of foraging spatial scales

Timing of activity can reveal an organism's efforts to optimize foraging either by minimizing energy loss through passive movement or by maximizing energetic gain through foraging. Here, we assess whether signals of either of these strategies are detectable in the timing of activity of daily, local movements by birds. We compare the similarities of timing of movement activity among species using six temporal variables: start of activity relative to sunrise, end of activity relative to sunset, relative speed at midday, number of movement bouts, bout duration and proportion of active daytime hours. We test for the influence of flight mode and foraging habitat on the timing of movement activity across avian guilds. We used 64 570 days of GPS movement data collected between 2002 and 2019 for local (non‐migratory) movements of 991 birds from 49 species, representing 14 orders. Dissimilarity among daily activity patterns was best explained by flight mode. Terrestrial soaring birds began activity later and stopped activity earlier than pelagic soaring or flapping birds. Broad‐scale foraging habitat explained less of the clustering patterns because of divergent timing of active periods of pelagic surface and diving foragers. Among pelagic birds, surface foragers were active throughout all 24 hrs of the day while diving foragers matched their active hours more closely to daylight hours. Pelagic surface foragers also had the greatest daily foraging distances, which was consistent with their daytime activity patterns. This study demonstrates that flight mode and foraging habitat influence temporal patterns of daily movement activity of birds.We thank the Nature Conservancy, the Bailey Wildlife Foundation, the Bluestone Foundation, the Ocean View Foundation, Biodiversity Research Institute, the Maine Outdoor Heritage Fund, the Davis Conservation Foundation and The U.S. Department of Energy (DE‐EE0005362), and the Darwin Initiative (19-026), EDP S.A. ‘Fundação para a Biodiversidade’ and the Portuguese Foundation for Science and Technology (FCT) (DL57/2019/CP 1440/CT 0021), Enterprise St Helena (ESH), Friends of National Zoo Conservation Research Grant Program and Conservation Nation, ConocoPhillips Global Signature Program, Maryland Department of Natural Resources, Cellular Tracking Technologies and Hawk Mountain Sanctuary for providing funding and in-kind support for the GPS data used in our analyses

Tracking data highlight the importance of human-induced mortality for large migratory birds at a flyway scale

Human-induced direct mortality affects huge numbers of birds each year, threatening hundreds of species worldwide. Tracking technologies can be an important tool to investigate temporal and spatial patterns of bird mortality as well as their drivers. We compiled 1704 mortality records from tracking studies across the African-Eurasian flyway for 45 species, including raptors, storks, and cranes, covering the period from 2003 to 2021. Our results show a higher frequency of human-induced causes of mortality than natural causes across taxonomic groups, geographical areas, and age classes. Moreover, we found that the frequency of human-induced mortality remained stable over the study period. From the human-induced mortality events with a known cause (n = 637), three main causes were identified: electrocution (40.5 %), illegal killing (21.7 %), and poisoning (16.3 %). Additionally, combined energy infrastructure-related mortality (i.e., electrocution, power line collision, and wind-farm collision) represented 49 % of all human-induced mortality events. Using a random forest model, the main predictors of human-induced mortality were found to be taxonomic group, geographic location (latitude and longitude), and human footprint index value at the location of mortality. Despite conservation efforts, human drivers of bird mortality in the African-Eurasian flyway do not appear to have declined over the last 15 years for the studied group of species. Results suggest that stronger conservation actions to address these threats across the flyway can reduce their impacts on species. In particular, projected future development of energy infrastructure is a representative example where application of planning, operation, and mitigation measures can enhance bird conservation