Falco Eleonorae Research Articles

Factors influencing the occurrence of Eleonora's falcon Falco eleonorae breeding colonies on Greek islands

During the breeding seasons of 2004‐2006, the population of Eleonora's falcon Falco eleonorae was censused on > 900 islands in the Ionian and the Aegean Seas, Greece. However, only one third of the islands hosted breeding pairs. With our study, we aim at understanding the factors that influence the occurrence of the species' breeding colonies on Greek islands. Thus, we developed generalised linear models for all candidate explanatory variables that according to previous studies are believed to influence the occurrence of the species. We identified the best set of models based on differences in the Akaike Information Criterion, and subsequently, we applied model averaging to estimate model average coefficients for those explanatory variables included in the best set of models. According to our results based on presence‐absence data from approximately 370 islands, the presence of breeding colonies is related to the coastline geomorphology, where steep cliffs with ledges are preferred. These geomorphologic characteristics are considered to offer protection from wave action and terrestrial intruders, as well as visual privacy to breeding pairs, and they have previously been associated with nest‐site selection. In addition, breeding colonies are more likely to be found on islands close to freshwater bodies and to other neighbouring colonies. Freshwater bodies constitute important foraging areas and provide a means to maintain the falcons' plumage in good condition. The clustered distribution pattern of the breeding colonies is probably due to the process of first‐time breeders' settlement and/or colony connectivity. Finally, in view of these preliminary results, we recommend actions to be taken in future studies in order to better understand the role of these factors during the species' breeding period.

Summer pre-breeding movements of Eleonora’s Falcon Falco eleonorae revealed by satellite telemetry: implications for conservation

SummaryRecent advances in bird tracking technologies are revealing that migratory birds use temporal staging sites other than breeding and wintering areas, and these areas deserve conservation efforts. Eleonora’s Falcon Falco eleonorae is a long-distance migratory raptor that breeds colonially on islands and is considered a priority species for conservation. Anecdotal observations indicate that during the pre-breeding period, Eleonora’s Falcons stay in inland areas far away from the colonies, but, to date there are no detailed data concerning the connectivity between these areas and breeding colonies. Using satellite telemetry, we analysed data from four summering events belonging to three individuals breeding in two colonies in the Western Mediterranean (Spain). All of them made inland movements in areas up to c.400 km distant from the respective breeding colonies, visiting several habitats, from forests to arable lands, probably taking advantage of high densities of insects. Perturbations occurring in these areas could threaten Eleonora’s Falcons with serious consequences at the population level. We suggest that conservation measures implemented at breeding and wintering grounds may not suffice and that temporary staging areas should be identified at a larger scale and deserve protection as well.

First records for South Sudan of African Cuckoo Hawk Aviceda cuculoides, Icterine Warbler Hippolais icterina and White-winged Widowbird Euplectes albonotatus, and first sighting of Eleonora's Falcon Falco eleonorae

First records for South Sudan of African Cuckoo Hawk Aviceda cuculoides, Icterine Warbler Hippolais icterina and White-winged Widowbird Euplectes albonotatus, and first sighting of Eleonora's Falcon Falco eleonorae

Ranging Behaviour of Eleonora's FalconsFalco eleonoraeDuring Chickrearing

The Eleonora's Falcon is a cliff-nesting raptor that breeds on isolated small islands adjusting its breeding season to coincide with the post-breeding autumn migration of its small passerine prey migrating over the sea, between late August and early October. Two adult female Eleonora's Falcons were equipped with Argos satellite transmitters during the chick-rearing period in Morocco giving the opportunity to study the ranging behaviour of the species during at least a part of the breeding season. Results showed that the falcons spent most of the time at sea during mornings, stayed mainly inland during afternoons, and rested in the colony during nights. Interestingly, although most distances were recorded shorter than 50 km away from the colony, movements took also place to areas located more than 100 km away. Locating and protecting these inland areas used for resting and foraging may be of interest for the conservation of the species in order to avoid perturbations such as poisoning and habitat destruction.

Multi‐temporal distribution modelling with satellite tracking data: predicting responses of a long‐distance migrant to changing environmental conditions

Summary1. Despite the wealth of data available from satellite tracking (ST) studies, such data have rarely been used to model species distributions. Using a novel method, we show how to exploit satellite data to analyse whether and how a migratory species responds to fluctuating environmental conditions in its wintering area. This is particularly crucial for establishing comprehensive conservation measures for rare species in areas that are threatened by increasing land use and climate change.2. We use ST data of Eleonora’s falcon Falco eleonorae, a long‐distance migratory raptor that winters in Madagascar, and assess the performance of static species distribution models (SDM) as well as multi‐temporal models. ST data were derived from seven falcons tracked during three consecutive wintering periods and for a total of 2410 bearings, of which 512 locations were used in SDMs. We employed environmental predictors (climate, topography and land cover) with a spatial resolution of 30 arc seconds (c. 1 km2) to match rigorously filtered ST data with an accuracy of ≤1 km.3. We first created a model with low temporal but high spatial resolution (half‐year). To predict suitable habitat for each month of the wintering season, we took advantage of the high temporal resolution inherent in ST data and employed temporally corresponding remote sensing data [Normalized Difference Vegetation Index (NDVI) 10‐day composites] together with other variables to create monthly models.4. We show that ST data are suited to build robust and transferable SDMs despite a low number of tracked individuals. Multi‐temporal SMDs further revealed seasonal responses of the study species to changing environmental conditions in its wintering area.5. Synthesis and applications. We present a transferable approach to predict the potential distribution of organisms as well as their dynamic response to changing environmental conditions. Future conservation management plans could include the prediction of a species’ reaction to changing land‐use practices or climate change based on the methodology proposed here. This would provide an early warning system for the decline of populations wintering in remote areas that underlie strong climatic fluctuations.

Wintering habitats of Eleonora's Falcons Falco eleonorae in Madagascar

Capsule Eleonora's Falcons wintering in Madagascar selected degraded humid forests and cultivated areas close to pristine humid forest. Aims To identify the habitat preferences of Eleonora's Falcon Falco eleonorae on their wintering grounds in Madagascar, and to use this information to gain insights into the conservation priorities of this species. Methods A total of 11 Eleonora's Falcons were captured in Spain in 2007 and 2008 and equipped with solar-powered satellite transmitters. We obtained information on five complete wintering events for three birds, two of them tracked for two consecutive years. Data were analyzed using geographic information system-based cartography. Results The analyses showed a preference for degraded humid forests and cultivated lands within areas where pristine humid forests were the most abundant habitat type. Conclusions Eleonora's Falcons could be taking advantage from a spill-over edge effect of their insect prey into cultivated and more open areas close to humid forests. However, the importance of humid forests for Eleonora's Falcons seems to be high. The current loss of this habitat in Madagascar is a cause for concern with respect to the conservation of this long-distance migratory falcon species.

Complementing the puzzle of Eleonora’s Falcon (Falco eleonorae) migration: new evidence from an eastern colony in the Aegean Sea

Eleonora’s Falcon (Falco eleonorae) is an endemic breeder of the Mediterranean Sea and the Canary Islands that overwinters in Madagascar and surrounding areas. Recent telemetry studies have revealed the migratory journey of falcons from the western and central Mediterranean breeding colonies. Our study complements the puzzle of the species’ migration providing data from an eastern Mediterranean breeding colony. In this paper, we describe for the first time the migratory routes of four falcons originating from the Aegean Sea, the core of the species’ breeding range. We tracked two adults and two immature siblings to their wintering grounds in Madagascar. According to our results, the timing of migration was consistent with previous studies. Our findings also suggest that the falcons adjust their flight speed according to the environmental conditions encountered en route, by accelerating during open-sea and desert crossings and by slowing down in potential foraging areas. Moreover, the selection of common staging areas, both among the two siblings and among the two adults, highlights the role of these areas in the migratory cycle of the species. Finally, according to the home-range analysis on the wintering grounds, space use was rather variable across the four tracked falcons. Still, the falcons were more frequently observed within the submontane forest, one of the last patches of primary rainforest in Madagascar. Thus, future studies aiming at unveiling the ecological requirements of the species in its wintering quarters are considered as top priority.

Migración e invernada del Halcón de Eleonora (Falco eleonorae Gené, 1839; falconidae): ¿qué hemos aprendido con el seguimiento por satélite?

In recent years, satellite tracking has enabled to get new important insights into several aspects of bird’s migration, one of the most unknown aspects of birds’ ecology. In the last years, we have studied the migration and wintering of satellite tracked Eleonora’s falcons (Falco eleonorae Gene, 1839) tagged during the breeding season at Balearic and Columbretes Islands. In autumn, Eleonora’s falcons migrated following inland routes along Africa. Birds arrived into Africa flying over the Mediterranean Sea directly from the breeding colonies, and then crossed the Sahara Desert, the Sahel region, south-eastern African savannahs and the Channel of Mozambique to arrive into their wintering grounds in Madagascar. During winter, falcons used areas of pristine humid forests close to degraded forests and cultivations, where they can fulfil food requirements for this period. In spring, falcons travelled larger over-sea distances between Madagascar and continental Africa than in autumn. We observed inter-annual variations in the routes used in this season to cross to inland Africa, which were related to meteorological conditions at the time of leaving Madagascar. These results are very important to propose global conservation actions for the species, highlighting that these actions should embrace the whole lifecycle of the species

Variation in breeding parameters of Eleonora's falcon (Falco eleonorae) and factors affecting its reproductive performance

AbstractWe gathered data for a four‐year period (2004–2007) on the nesting ecology and reproductive performance of Eleonora's falcon in the Aegean Sea. We investigated in an indirect way the relation between clutch size and pre‐laying food availability, the significance of site and pair quality on productivity, and the effects of habitat and intraspecific competition on breeding success. Overall, the species selected nest sites sheltered from sun exposure but not from the prevailing wind. Hatching, fledging, and breeding success rates were estimated at 64, 72%, and 60%, respectively. Fledglings per breeding pair ranged from 1.19 to 1.75, and fledglings per successful pair from 1.84 to 2.0, between the years. Productivity depended on parental care rather than nest‐site quality. Breeding parameters varied significantly between the years, exhibiting a strong spatial yet local effect. Low success rates were recorded in specific colonies, which were attributed to adverse weather conditions and habitat degradation. Insect food availability prior to egg‐laying, estimated via plant biomass, was positively correlated to clutch size. Meanwhile, low wind strengths in August, large distances from the mainland, and population size in the vicinity of the colonies had negative effects on breeding success. Considering data at the Mediterranean scale, a longitudinal trend is observed across the breeding range of this species, with breeding parameters slightly decreasing from west to east.

Nest-site preferences of Eleonora’s Falcon (Falco eleonorae) on uninhabited islets of the Aegean Sea using GIS and species distribution models

Eleonora’s Falcon breeds colonially on small islands of the Mediterranean Sea and Macaronesia. Despite the wealth of papers highlighting the importance of nesting characteristics on this species’ breeding performance, few have addressed the issue of nest-site selection explicitly. In this paper, we develop presence–absence and presence-pseudoabsence models to predict nest occurrence as a function of the topography of the nesting territory. Nest occurrence data were available for nine uninhabited islets of the Aegean Sea, within which the majority of the global population of Eleanora’s Falcon is encountered. Our findings suggest that the presence of conspecifics together with certain topographic features according to the surface area of the islet being studied can be used to predict nest occurrence on uninhabited islets of the Aegean Sea. We conclude that predictive models characterized by flexibility and/or the use of absence data that also consider nest clustering can result in robust predictions of the nest occurrence of Eleonora’s Falcons in Greek breeding colonies and eventually facilitate future monitoring schemes. Since this is the first time nest-site preferences of Eleonora’s Falcon have been analyzed using species distribution models, we encourage the application of similar methodologies to other areas within the species’ breeding range to further validate our findings.

Antioxidant machinery differs between melanic and light nestlings of two polymorphic raptors.

Colour polymorphism results from the expression of multiallelic genes generating phenotypes with very distinctive colourations. Most colour polymorphisms are due to differences in the type or amount of melanins present in each morph, which also differ in several behavioural, morphometric and physiological attributes. Melanin-based colour morphs could also differ in the levels of glutathione (GSH), a key intracellular antioxidant, because of the role of this molecule in melanogenesis. As GSH inhibits the synthesis of eumelanin (i.e. the darkest melanin form), individuals of darker morphs are expected to have lower GSH levels than those of lighter morphs. We tested this prediction in nestlings of two polymorphic raptors, the booted eagle Hieraaetus pennatus and the Eleonora's falcon Falco eleonorae, both of which occur in two morphs differing in the extent of eumelanic plumage. As expected, melanic booted eagle nestlings had lower blood GSH levels than light morph eagle nestlings. In the Eleonora's falcon, however, melanic nestlings only had lower GSH levels after controlling for the levels of other antioxidants. We also found that melanic female eagle nestlings had higher levels of antioxidants other than GSH and were in better body condition than light female eagle nestlings. These findings suggest an adaptive response of melanic nestlings to compensate for reduced GSH levels. Nevertheless, these associations were not found in falcons, indicating species-specific particularities in antioxidant machinery. Our results are consistent with previous work revealing the importance of GSH on the expression of melanic characters that show continuous variation, and suggest that this pathway also applies to discrete colour morphs. We suggest that the need to maintain low GSH levels for eumelanogenesis in dark morph individuals may represent a physiological constraint that helps regulate the evolution and maintenance of polymorphisms.

Prevalence of Neutralizing Antibodies to West Nile Virus in Eleonora's Falcons in the Canary Islands

Birds are the major amplifying host for West Nile virus (WNV), a flavivirus that may affect humans and transmitted by bloodsucking vectors. Eleonora's Falcons (Falco eleonorae) migrate to the Canary Islands annually from WNV-endemic regions. To investigate the possible role of Eleonora's Falcons in the circulation of WNV, we measured WNV-specific antibodies in 81 falcons captured in 2006. None of the nestlings but 14.8% of the adults had WNV-neutralizing antibodies. RT-PCR did not detect flaviviruses in nonculicine ectoparasites (n=231) of the falcons. These findings suggest that WNV infection did not occur locally, but rather on the wintering grounds or during migration.

Weather conditions promote route flexibility during open ocean crossing in a long-distance migratory raptor

Weather conditions are paramount in shaping birds' migratory routes, promoting the evolution of behavioural plasticity and allowing for adaptive decisions on when to depart or stop during migration. Here, we describe and analyze the influence of weather conditions in shaping the sea-crossing stage of the pre-breeding journey made by a long-distance migratory bird, the Eleonora's falcon (Falco eleonorae), tracked by satellite telemetry from the wintering grounds in the Southern Hemisphere to the breeding sites in the Northern Hemisphere. As far as we know, the data presented here are the first report of repeated oceanic journeys of the same individuals in consecutive years. Our results show inter-annual variability in the routes followed by Eleonora's falcons when crossing the Strait of Mozambique, between Madagascar and eastern continental Africa. Interestingly, our observations illustrate that individuals show high behavioural plasticity and are able to change their migration route from one year to another in response to weather conditions, thus minimising the risk of long ocean crossing by selecting winds blowing towards Africa for departure and changing the routes to avoid low pressure areas en route. Our results suggest that weather conditions can really act as obstacles during migration, and thus, besides ecological barriers, the migratory behaviour of birds could also be shaped by "meteorological barriers". We briefly discuss orientation mechanisms used for navigation. Since environmental conditions during migration could cause carry-over effects, we consider that forecasting how global changes of weather patterns will shape the behaviour of migratory birds is of the utmost importance.

Cadmium, lead, and mercury levels in feathers of small passerine birds: Noninvasive sampling strategy

Bird feathers have been widely used as a nondestructive biological material for monitoring heavy metals. Sources of metals taken up by feathers include diet (metals are incorporated during feather formation), preening, and direct contact with metals in water, air, dust, and plants. In the literature, data regarding the origin of trace elements in feathers are not univocal. Only in the vast literature concerning mercury (as methyl mercury) has endogenous origin been determined. In the present study, we investigate cadmium, lead, and mercury levels in feathers of prey of Falco eleonorae in relation to the ecological characteristics (molt, habitat, and contamination by soil) of the different species. Cluster analysis identified two main groups of species. Differences and correlations within and between groups identified by cluster analysis were then checked by nonparametric statistical analysis. The results showed that mercury levels had a pattern significantly different from those of cadmium and lead, which in turn showed a significant positive correlation, suggesting different origins. Nests of F. eleonorae proved to be a good source for feathers of small trans-Saharan passerines collected by a noninvasive method. They provided abundant feathers of the various species in a relatively small area--in this case, the falcon colony on the Isle of San Pietro, Sardinia, Italy.

All across Africa: highly individual migration routes of Eleonora's falcon

Eleonora's falcon (Falco eleonorae) is a rare raptor species that delays its breeding period until late summer to feed its young with passerines at the peak of autumn migration. Since the 1950s, this slender winged falcon has been believed to migrate along a historical route via the Red Sea to its main wintering area in Madagascar. In our study, we used satellite telemetry to investigate the real migration route of Eleonora's falcons and found that the species displayed a highly individual migration pattern. Furthermore, juvenile falcons migrated via West Africa to Madagascar and two juveniles could be tracked during spring migration and to their summering areas in East and West Africa. As juveniles migrated independently of adults, we discuss inherited navigation strategies forming part of a complex navigation system. We propose the idea of an orientation mechanism that naive falcons could apply during their long-distance migration towards their faraway wintering area located in the open ocean.

The status of Eleonora’s Falcon (Falco eleonorae) in Greece

With more than 80% of the species global population breeding in Greece, Eleonora’s Falcon (Falco eleonorae) is reported to be the most important bird species in the country. A national population survey was conducted during the breeding seasons 2004–2006 in order to assess the species' breeding distribution and population size. This census was the first of its kind and was part of a global population survey, involving more than 80 field workers. Standard field protocols, described in the International Species Action Plan, and a GIS interactive database were developed. Data were stored and spatially explored in conjunction to historical information and past records. A total of about 17,660 falcons were counted or an estimated 12,300 breeding pairs, which were concentrated in six major regions, i.e., northeast Aegean, Sporades, east Cyclades, Antikythira, southwest Dodecanese and the satellite islets of eastern Crete. Compared to previous descriptions of breeding colonies and population status, spatial variation in site occupancy was detected with a population decline in one of the aforementioned regions and an apparent increase in all the rest. The results of this national survey, expected to be repeated every 10 years, provided guidance for reviewing the conservation status of Eleonora’s Falcon in Greece and baseline information for future monitoring of its population.

The role of forensic geoscience in wildlife crime detection

The increase in both automation and precision in the analysis of geological materials has had significant impact upon forensic investigations in the last 10 years. There is however, a fundamental philosophical difference between forensic and geological enquiry. This paper presents the results of forensic geoscientific investigations of three cases of wildlife crime. Two cases involve the analysis of soils recovered after incidents of illegal badger baiting in the United Kingdom. The third case involves the illegal importation of Eleonora's Falcon ( Falco eleonorae) into the United Kingdom from the Mediterranean. All three cases utilise the analysis of soils by a variety of physical, chemical and biological techniques. These involve mineral and grain size analyses, cation and anion compositions, pH, organic content and pollen analysis. The independent analysis undertaken by specialists in each of these three main fields conclude firstly, that there is a significant similarity between sediments taken at the crime site at both badger setts and with sediments recovered from various spades, shovels and clothing belonging to suspects and secondly, that the soils analysed associated with the removal of the falcon eggs in the Mediterranean contained characteristics similar in many respects to the soils of the breeding areas of F. eleonorae on the cliffs of Mallorca. The use of these independent techniques in wildlife crime detection has great potential given the ubiquitous nature of soils and sediments found in association with wildlife sites.

Erratum to: The study of nest-site preferences in Eleonora’s falcon Falco eleonorae through digital terrain models on a western Mediterranean island

This study addresses nesting-site preferences in Eleonora’s falcon Falco eleonorae by means of geographic information systems and high-quality high-resolution digital terrain models (DTMs). A small western Mediterranean archipelago (Columbretes Islands) with a colony of 34 pairs was chosen as a case study. Overall, 21 grid variables obtained from DTM were considered of which 12 showed a significant effect. Four of them were topographic (i.e. elevation, X-axis aspect, slope and curvature), four climatic (i.e. wind exposure, solar insolation, solar radiation and radiation index), three anthropogne (visibility of lighthouse beam, visibility of antropic zones and distance to antropic zones) and one biotic (vegetation cover). Falcon nests were placed on pixel cells with lower average insolation and radiation than cells without nests, but had higher values of wind exposure. Nests were built on concave sites mainly with an easterly facing aspect and steep slopes. Falcons were shown to respond to human presence as all antropic variables considered had a significant effect. The results have a number of management and conservation implications, because the knowledge of nesting preferences of the species allows the proper design of sanctuaries and an appropriate human use of these areas.

The study of nest-site preferences in Eleonora’s falcon Falco eleonorae through digital terrain models on a western Mediterranean island

The study of nest-site preferences in Eleonora’s falcon Falco eleonorae through digital terrain models on a western Mediterranean island

Long-term changes of species richness in a breeding bird community of a small Mediterranean archipelago

We analyzed the pattern of species richness changes in a bird–breeding bird community on a small western Mediterranean archipelago (Columbretes Islands) over a 40–year period (1964–2003). The aim of this study was to qualitatively account for the relative roles of local and regional factors in shaping the community. As expected, we found that regional factors (at the metapopulation spatial scale) increased diversity whereas local factors (i.e. ecological) probably prevented further increases in diversity. We found that the archipelago gained four new species (two seabirds and two falconids) during the study period, whereas no extinctions were recorded. The community seems partially or completely closed to some groups of species (e.g. small–sized birds such as passerines and storm–petrels), probably owing to predatory exclusion by Eleonora falcons (Falco eleonorae). As newly arrived species have breeding calendars that do not fully overlap with those of resident species, competition for space in a rather saturated area is prevented. Preservation of rare species which increase gamma (regional) diversity rather than alpha diversity with common species should be the main local conservation goal.