ORIGINAL ARTICLE

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

Christina Kassara • Jakob Fric • Marion Gschweng •

Spyros Sfenthourakis

Received: 7 May 2011 / Revised: 1 September 2011 / Accepted: 16 December 2011 / Published online: 18 January 2012

� Dt. Ornithologen-Gesellschaft e.V. 2012

Abstract 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 Mediter-

ranean 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 Madagas-

car. 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 accel-

erating 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.

Keywords Eleonora’s Falcon � Satellite telemetry �Overwintering � Home range � Madagascar � Aegean Sea

Zusammenfassung

Ein weiterer Beitrag zur Losung des Ratsels uber den

Zugweg des Eleonorenfalken (Falco eleonorae): neue

Erkenntnisse aus einer ostlichen Kolonie in der Agais

Der Eleonorenfalke (Falco eleonorae) ist ein Brutvogel,

der ausschließlich auf Mittelmeerinseln und den Kanaren

brutet und der in Madagaskar uberwintert. Durch neuere

Telemetriestudien konnte der Verlauf der Zugwege von

Falken aus westlichen und zentralen Brutkolonien ermittelt

werden. Die vorliegende Studie vervollstandigt die bis-

herigen Erkenntnisse, da sie Daten zu den Zugwegen von

Falken aus den ostlichen Kolonien liefert. Hier zeigen wir

erstmals die Zugrouten von vier Falken aus dem ostlichen

Verbreitungsareal der Agais, dem Hauptverbreitungsgebiet

des Eleonorenfalken. Wir verfolgten zwei adulte Falken

und zwei juvenile Nestgeschwister per Satellitentelemetrie

bis zu ihrem Uberwinterungsgebiet auf Madagaskar. Un-

sere Ergebnisse zum zeitlichen Ablauf des Zuges stimmen

mit denen fruherer Studien uberein. Wir fanden außerdem

Communicated by F. Bairlein.

C. Kassara (&) � S. Sfenthourakis

Section of Animal Biology, Department of Biology,

University of Patras, 26500 Patras, Greece

e-mail: ckassara@upatras.gr; cristina.kassara@gmail.com

J. Fric

Hellenic Ornithological Society/Birdlife-Greece,

Vasileos Herakliou 24, 10682 Athens, Greece

M. Gschweng

Institute of Experimental Ecology, University of Ulm,

89069 Ulm, Germany

M. Gschweng

Global Concepts for Conservation, 89173 Lonsee, Germany

123

J Ornithol (2012) 153:839–848

DOI 10.1007/s10336-011-0802-2

heraus, dass die Falken ihre Zuggeschwindigkeit an die

wahrend des Zuges auftretenden Bedingungen anpassen,

indem sie wahrend der Uberquerung großerer Wasser-

massen die Geschwindigkeit steigern und diese in fur die

Jagd geeigneten Gebieten drosseln. Daruber hinaus zeigt

die Wahl von Rastgebieten sowohl bei den adulten als auch

bei den juvenilen Falken deren Bedeutung wahrend des

Zuges. Durch eine Analyse der Aktionsraume im Winter-

gebiet fanden wir heraus, dass die raumliche Nutzung des

Habitats innerhalb der untersuchten Individuen sehr vari-

abel war. Insgesamt wurden die Falken haufiger in sub-

montanem Regenwald lokalisiert, einem der letzten

zusammenhangenden Regenwaldgebiete Madagaskars.

Zukunftige Studien zu den okologischen Habitatanforde-

rungen der Eleonorenfalken in ihren Winterquartieren soll-

ten daher als oberste Prioritat angesehen werden.

Introduction

Up to the late 1970s, ringing recoveries and direct obser-

vations were the only tools available for the study of bird

migration, yet providing information for only a part of the

overall migratory journey (e.g. Ristow 1975; Delgado and

Quilis 1990; Thorup et al. 2003). With the emergence of

satellite telemetry and the development of sophisticated

transmitters, scientists are now able to accurately assess and

sometimes reconsider key aspects of bird migration, such as

the geography of migratory routes, travelling decisions in

relation to energetic demands and weather conditions,

existence of migratory flyways and ecological barriers, and

the location of important stopover areas, wintering and

summering sites (e.g. McGrady et al. 2006; Gschweng et al.

2008; Lopez-Lopez et al. 2010; Mellone et al. 2010).

Among the most recent and typical examples of such

studies is the case of Eleonora’s Falcon (Falco eleonorae

Gene, 1839). This medium-sized long-distance migrant

breeds exclusively in the Mediterranean basin, the Canary

Islands and the NW coast of Africa, and overwinters in

Madagascar, SE Africa and on islands of the Indian Ocean

(Walter 1979). Although the breeding distribution of the

species is well defined, new data and information about the

wintering grounds, the summering sites of the immature

birds and the migratory paths they follow, are currently

being brought to light (Gschweng et al. 2008; Lopez-Lopez

et al. 2010). Until recently, all breeding populations were

believed to undertake a common migratory route through

the Red Sea, along the coastline of the African continent,

until they reached Madagascar (Stresemann 1954). By the

early 1990s, scientists started to doubt this theory due to

new data from ring recoveries (Delgado and Quilis 1990).

However, it was not until 2008 that this hypothesis was

tested with hard data, when 13 Eleonora’s Falcons were

tagged with satellite transmitters in Sardinia, Italy, and

their migratory routes were investigated in detail (Gschw-

eng et al. 2008). It is now known that during the southward

autumn migration Eleonora’s Falcons from central Medi-

terranean (Gschweng et al. 2008) and western Mediterra-

nean colonies (Lopez-Lopez et al. 2010) literally cross

Africa to reach their wintering grounds. Despite the

observed inter-individual variability in the selected path-

ways (Gschweng et al. 2008; Lopez-Lopez et al. 2010), the

falcons’ routes converge over eastern Mozambique before

crossing the Mozambique Channel in an attempt to mini-

mise the distance; hence, the energetic cost of crossing

several hundred kilometers over water (Lopez-Lopez et al.

2010). Until this study, satellite data of the spring migra-

tion were only known for two adult and two juvenile

Eleonora’s Falcons from Sardinia. As expected, the adults

returned to their breeding colonies, but surprisingly the two

yearlings spent their summer in two geographically distinct

regions in Africa (Gschweng et al. 2008).

Moreover, the ecology and distribution of the species

within its wintering area has been only roughly studied

(Ristow 2010). Current knowledge has been based so far on

sporadic visual observations (Zefania 2001) and published

country lists (e.g. Milon et al. 1973; references in Ristow

and Wink 1992–1994 and in Ristow 2010). Thus, the

exploration of Eleonora’s Falcon migration has just started

and many of its aspects are yet to be discovered. Due to its

wide breeding range and localised breeding areas, the

investigation of the migratory routes of individuals origi-

nating from other breeding regions, especially from those at

the margins of the species’ distributional range, is a top

priority in order to complete the puzzle of the species’

migration.

Here, we describe for the first time the migration of

Eleonora’s Falcons from one of the eastern Mediterranean

colonies located in the central Aegean Sea. The Greek

archipelago hosts more than 80% of the global breeding

population (Dimalexis et al. 2008). Therefore, it is essential

not only to track but also to identify the factors that shape

the migratory pattern of individuals originating from the

centre of the species’ breeding range. Considering avail-

able information from ring recoveries, direct observations

and previous satellite-tracking studies, we highlight dif-

ferences in the phenology of their voyage from the

breeding colonies to Madagascar and back. In addition, we

investigate variability in migration speed as a response to

wind speed, time of the day, latitude and season. Finally,

we delineate home ranges within the wintering grounds for

the four tracked falcons, based on kernel density estima-

tors, making the first step in understanding space use and

habitat selection during this least known part of the spe-

cies’ life cycle.

840 J Ornithol (2012) 153:839–848

123

Methods

Tag deployment and operation

We captured four Eleonora’s Falcons on an uninhabited

islet located in the central Aegean Sea, two adults during

the incubating period and two siblings during the fledgling

period (Table 1). The four individuals were tagged with

9.5-g solar-powered transmitters (Microwave Telemetry).

In order to ensure maximum longevity and hence track the

birds during multiple migratory seasons, the tags were

programmed on a ‘6 h ON/16 h OFF’ duty cycle during the

autumn migratory period (August–December), ‘6 h ON/

70 h OFF’ during the wintering period (January–February)

and ‘6 h ON/34 h OFF’ during the spring migratory period

(March–May). The tags were attached with harness as

backpacks (see Gschweng et al. 2008). After tag deploy-

ment, the adults were released immediately and the fledg-

lings were placed back to their nests.

Sex determination

Sex determination via morphological characters was only

possible for the two adults. For the two juveniles. we took

blood samples and conducted molecular analyses as

described in Fridolfsson and Ellegren (1999) and modified

by Wang et al. (2007), targeting two different introns of the

CHD1 gene.

Migratory period

The reconstruction of the migratory journey was based on

high-quality satellite locations (Argos classes 0–3; Argos

2008), which comprised ca. 74% of the total number of

received fixes. In order to investigate the effect of latitude,

time of day, season and wind on the observed migration

speed of the four falcons, we considered path segments of

consecutive locations separated by 1–4 h for speed esti-

mation. We divided the autumn and spring migratory

routes into latitudinal bands of 10� width and assigned each

path segment to the respective band according to the value

of the latitude of the central point. Next, we classified the

path segments into day- or night-travelling according to the

local time of their final location by taking into consider-

ation the duration of civil twilight at that location (http://

aa.usno.navy.mil/). We used the National Center of Envi-

ronmental Prediction Reanalysis data archives (www.cdc.

noaa.gov/cdc/data.nmc.reanalysis.html) to extract wind

data at both the 850 and 925 mb pressure level, since the

actual flight altitude for the four falcons was unknown.

Mean daily speed of wind components along the west–east

and north–south axes were provided at a spatial resolution

of 2.5� latitude by 2.5� longitude global grid. Then, the

overall wind speed and wind direction were estimated via

trigonometric and algebraic functions at the central point

and based on the middle date of each path segment con-

sidering local time. Wind direction was then classified as

tailwind, headwind, clockwise or counterwise in relation to

the bearing of each path segment. We fitted Generalized

Linear Models (GLMs) considering both the main and

interaction effects of four independent variables, namely

latitudinal class, time of day, season and wind for each

pressure level. The latter was modelled as the combined

effect of wind speed and wind direction. All statistical

analyses were implemented in SPSS 18.0 (SPSS 2009),

while spatial analyses and map creation were processed

with ArcGIS 9.2 (ESRI 2006).

Wintering period

We created home-range areas within the wintering grounds

for each individual based on day-time high-quality loca-

tions (Argos classes 1–3; Argos 2008), projected in UTM

coordinates (UTM 38S zone). First, we estimated the uti-

lization distribution, i.e. the probability density of finding

an individual in a given location, by creating fixed kernels

up to 95% probability. Then, we computed the amount of

overlap between every pair of kernels, based on the

Table 1 Autumn and spring migration of four Eleonora’s Falcons (Falco eleonorae) originating from Greece recorded by satellite telemetry

ID Tag no. Sex Weight (g) Autumn migration Spring migration

Migratory

period

No. of

travelling

days

Distance

covered

(km)

Migratory

period

No. of

travelling

days

Distance

covered

(km)

Adult 1 94118 F 415 21 (20) Oct–12 Nov 24 7,966 14 (13) Apr–1 May 14 6,740

Adult 2 94119 F 415 23 (21) Oct–5 Nov 15 7,030 13 (12) Apr–7 May 13 4,917

Juvenile 1 94120 M 480 22 (20) Oct–16 Dec 26 12,063 15 (15) Apr–11 Jun 33 11,827

Juvenile 2 94121 F 490 24 (23) Oct–30 Nov 22 9,276 6 (6) May–13 May 7 3,436

Estimated departure dates (no precise data available) in parentheses; instead dates of first signal received on migration are indicated. In spring

time, we were able to track the four falcons for only a part of their inbound journey; hence, the end dates refer to the date the signal was lost

J Ornithol (2012) 153:839–848 841

123

Utilization Distribution Overlap Index (UDOI), proposed

by Fieberg and Kochanny (2005). The UDOI not only

assesses the degree of overlap in space between two given

individuals but also accounts for the underlying probability

distribution of each individual within the intersected area.

Thus, UDOI equals one when the utilization distributions

are identical and coincide in space, while smaller values

are indicative of less overlap relative to uniform space use

and larger values suggest larger overlap relative to uniform

space use. We finally calculated the frequency of fixes

occurring within different types of habitat (Global Land

Cover Project 2000, http://bioval.jrc.ec.europa.eu/products/

glc2000/glc2000.php) and tested whether the falcons

exploited certain habitats more frequently than expected by

chance alone, by means of a v2-test. Home-range analyses

were implemented in R v2.10.1 (R Development Core

Team 2009; package ‘adehabitat’, Calenge 2006), while

statistical analyses were carried out in SPSS 18.0.

Results

Autumn migration

In autumn 2009, all four falcons began their migratory

journey between 20 and 24 October (Table 1). Henceforth

the individuals tagged with transmitters 94118, 94119,

94120 and 94121 will be referred to as adult 1, adult 2,

juvenile 1 and juvenile 2, respectively (Table 1). After

travelling on average 9,000 km (SD = ±2,189), the falcons

ended up in Madagascar to winter (Fig. 1; Table 1). The

two adults, sexed as females, headed SSE and completed

Fig. 1 Autumn migration

routes for two adult and two

juvenile Eleonora’s Falcons

(Falco eleonorae) originating

from an Aegean island colony in

Greece towards their wintering

grounds in Madagascar

842 J Ornithol (2012) 153:839–848

123

their journey within 15 and 24 days, respectively (Table 1).

After crossing the Sahara Desert, the two juveniles, sexed as

male (juvenile 1) and female (juvenile 2), following quasi-

parallel routes headed SW towards Chad and the Central

African Republic, where they made a substantial stopover

for approximately 15 days (Fig. 1). The two siblings con-

tinued their journey heading SE towards Mozambique,

where juvenile 2 crossed the Mozambique Channel and

landed on Madagascar, while juvenile 1 spent another

2 weeks foraging in Mozambique before crossing the

Channel (Fig. 1). Thus, migration lasted 38 days for juve-

nile 2 and 57 days for juvenile 1 (Table 1).

Spring migration

The timing of spring migration varied among the tagged

individuals. Adult 2 was the first to leave Madagascar by

mid-April, followed by adult 1 with only 1 day difference,

and juvenile 1 with 2 days difference. Juvenile 2 remained

in Madagascar until the beginning of May (Table 1). We

were able to track the four falcons for only a part of their

spring migration. Following a more eastern route in rela-

tion to the autumn tracks, both adults headed north and

flew over Tanzania, Kenya and Ethiopia. Adult 1 continued

over Somalia and Saudi Arabia, while the last signal was

sent from Cyprus, 18 days after the onset of its migration

and after having covered a distance of ca. 6,800 km. Adult

2 wandered close to the Red Sea coastline of Saudi Arabia,

where signals were lost 6 days later. During the 24 days of

satellite tracking, adult 2 had covered a distance of ca.

7,000 km (Table 1; Fig. 1).

Both juveniles crossed Mozambique, Tanzania and

Kenya (Fig. 2). Juvenile 1 continued its journey over

Sudan, the Central African Republic, Chad and Libya,

where signal transmission was interrupted on the 57th day.

By that time, the bird had covered a distance of 10,600 km.

It was relocated 2 months later in Italy, more than 1,000 km

from its previous location. Unfortunately, the exact route to

Italy remains unknown. Juvenile 2 reached Kenya after

8 days of travel, after having crossed ca. 3,000 km. Signal

transmission became erratic some days later and, given the

technical information at hand, we assume that the tag fell

off the bird.

Staging areas

The selection of stopover areas and the time spent there

indicated an age-specific pattern depending on the migra-

tory period. In autumn, adult 1 and 2 did not interrupt their

trip for more than a couple of days. In contrast, during

spring migration, after 4 and 7 days of travelling, respec-

tively, they stopped over the Ethiopian highlands. Their

movements were restricted to the east of the Great Rift

Valley, over the ecoregion of Somali Acacia-Commiphora

bushland and thicket. Adult 1 also explored higher altitude

areas within the ecoregion of the Ethiopian Montane For-

est. The flight behaviour of the two siblings was very

similar during both migratory periods. In autumn, after ca.

10 days of travelling, the two juveniles wandered around

the East Sudanian and Sahelian Acacia Savannah in central

Africa for 2 weeks before continuing southeast. Juvenile 1

interrupted its journey again 15 days later for a couple of

weeks in Mozambique, before crossing the Mozambique

Channel to Madagascar. In spring, both juveniles stopped

over in Kenya at areas of higher altitude than those in

autumn, which belong to the ecoregions of the northern

Acacia-Commiphora bushland and thicket and the East

African Montane Forest, similar to the adults. The where-

abouts of juvenile 2 remain unknown since then. Juvenile 1

spent 20 days in Kenya and then travelled for 7 days

towards central Africa, where it remained for another

2 weeks, before resuming its trip.

Migration speed in relation to latitude, sun, wind

and season

Wind did not appear to have any statistically significant

effect on the migration speed of the four falcons. On the

other hand, the time of day and the combined effect of

latitude and period of migration explained approximately

30% of the variance found in migration speed

(F6 = 13.830, P \ 0.001). Without considering the latitu-

dinal band 20�N–30�N due to the limited number of path

segments fulfilling the criteria of the analysis, we observe

that during day-time travelling the falcons accelerated in

the beginning (mean = 27.2 km/h) and towards the end of

the autumn migration (mean = 26.4 km/h). Thus, the

mean speed rate exhibited a U-shape distribution (Fig. 3),

which was reversed during spring migration (mean = 28.8

and 49.2 km/h, respectively).

Wintering period

The four falcons spent on average 146 days (SD ±18) in

Madagascar. Although all of them restricted their move-

ments within what is known as the humid forest area

(Harper et al. 2007) in the northern and especially the

north-eastern part of Madagascar, the home-range analysis

indicated considerable inter-individual variability in space

use (Fig. 4). The degree of overlap between the individual

home ranges was relatively low (Table 2), suggesting that

the probability of finding any of the two compared indi-

viduals within the intersected area was not equal (Fieberg

and Kochanny 2005). More specifically, the UDOI was

highest between adult 2 and juvenile 2 (Table 2) because a

considerable portion of the 50% home range of the former

J Ornithol (2012) 153:839–848 843

123

intersected the 50% home range of the latter (Fig. 4). In

contrast, the UDOI between adult 2 and juvenile 1 was the

smallest, not only because their intersected area equalled

half that of the previous pair but also because it consisted

of portions of the 95% home range of adult 2 and the 50%

home range of juvenile 1 (Fig. 4). Among the four tracked

falcons, adult 2 was by far the less mobile and, thus, its

estimated 95% home range area was 5,700 km2, followed

by juvenile 1 with an area of 14,700 km2 (Table 2). In

contrast, adult 1 and juvenile 2 changed their centre of

activity more frequently; hence, their estimated 95% home

range areas were ca. 33,000 km2 (Table 2). Despite the

observed variability, our results indicate a statistically

significant association between the location of the satellite

fixes and the type of habitat (v52 = 121.958, P \ 0.001),

Fig. 2 Spring migration routes

for two adult and two juvenile

Eleonora’s Falcons from

Madagascar towards their

summering sites. Signal

transmission was interrupted or

became erratic before the

completion of the journey for all

four falcons. In the case of

juvenile 1, the PTT went silent

for ca. 2 months and then was

reactivated for unknown reasons

while the falcon was in Italy

(location with a question mark)

Fig. 3 Mean speed (km/h) estimated for latitudinal bands of 10�width and for day and night-travelling path segments during two

migration periods

844 J Ornithol (2012) 153:839–848

123

with ca. 40% of the relocations occurring in areas of sub-

montane forest, ranging from 900 to 1,500 m altitude and

dominated by evergreen rainforests.

Discussion

Timing of migration

In the current study, we tracked the migration of four

Eleonora’s Falcons from their breeding colony in the

Central Aegean Sea towards their wintering grounds in

Madagascar and back.

The timing of autumn departure from the breeding

colony during the last 10 days of October is in agreement

with similar telemetry studies from Italy (Gschweng et al.

2008) and Spain (Lopez-Lopez et al. 2010). A different

pattern was observed in spring time; the departure dates of

the four falcons we monitored spanned a considerable

period, from mid-April to the beginning of May. Gschweng

et al. (2008) also report that one juvenile left its wintering

ground in the Democratic Republic of Congo on 11 April,

followed by one adult female that left Madagascar on 19

April, while a second adult female began its migration

4 days later and another juvenile on 7 May. Mellone et al.

(2010) report a narrow time-window for the departure of

three adult Eleonora’s Falcons from Madagascar in two

consecutive years. The birds left their wintering grounds

between 11 and 12 April in 2009 and between 13 and 14

April in 2010. Hence, whether late spring departures from

Madagascar are more typical for juveniles than for adults

remains an open question.

Fig. 4 Estimated home ranges for four Eleonora’s Falcons in Madagascar during wintering based on 95% fixed kernel contours

Table 2 Estimated home range

areas for four Eleonora’s

Falcons on their wintering

grounds in Madagascar based

on 95% fixed kernel contours,

compared with the Utilization

Distribution Overlap Index

(UDOI)

ID No. of

relocations

95% kernel

area (km2)

UDOI

Adult 1 Adult 2 Juvenile 1 Juvenile 2

Adult 1 34 33,405 – 0 0 0.099

Adult 2 93 5,726 0 – 0.095 0.238

Juvenile 1 55 14,780 0 0.095 – 0.125

Juvenile 2 104 32,282 0.099 0.238 0.125 –

J Ornithol (2012) 153:839–848 845

123

The arrival of adult Eleonora’s Falcons to their breeding

colonies cannot be accurately assessed, since during the

pre-breeding period the falcons tend to disperse several

kilometres from the colonies in search for food. Given the

information we have at hand from our satellite-tracked

adults, the two adult falcons could not have arrived in

Greece before mid-May. Such late arrivals are not

unknown to the species. In the past, one Italian female

adult completed its journey back to its breeding colony in

late May, while another one did not return before mid-

September (Gschweng et al. 2008), indicating a probably

atypical behaviour for the species.

Staging areas

Throughout the migratory period, the four falcons made

extended stopovers in shrublands and forested areas of

Ethiopia, Kenya, Mozambique and the border between

Chad and the Central African Republic. Eleonora’s Falcon

is mainly an insectivorous species that changes its diet

composition only in the course of the breeding period,

during which it feeds on passerine migrants (Walter 1979).

Just before the onset of migration and along the migratory

routes, Eleonora’s Falcons have been repeatedly observed

feeding on insects (Archer 1937 in Stresemann 1954; ref-

erences in Ristow and Wink 1992–1994). The correlation

between seasonal variation in insect abundance and cli-

matic variables, such as rainfall, has been documented

before for different places in Africa (Janzen and Schoener

1968; Poulin et al. 1992). Abundance of herbivorous

insects varies with the periodicity of vegetation growth,

which in turn is related to rainfall (Janzen and Schoener

1968; Poulin et al. 1992; Cumming and Bernard 1997).

Therefore, if we consider the seasonal pattern of rainfall

across the African continent, equatorial regions, such as the

selected staging areas, receive great amounts of rainfall

from late spring until late autumn; hence, they are expected

to host an increased biomass of insects during that time of

the year. This could also explain the reason why in a

previous study two immature juveniles chose to stay over

in Africa during summer (Gschweng et al. 2008).

The observed resemblance in migratory behaviour

between the two siblings of our study, but also among

individuals originating from geographically distinct

breeding colonies, deserves further investigation. Either

these similarities could be indicative of a common inher-

ited orientation programme (Helbig 1996) or they could

have arisen as a response to increased insect abundance at

specific locations. In particular, in autumn, the two adults

in our study assumed an approximately non-stop flight

towards Madagascar, while in spring both stopped in

Ethiopia for 2 weeks, similar to two other adults and one

juvenile from Italy in 2004 and 2006, respectively

(Gschweng et al. 2008). In addition, the interruption of the

juveniles’ migratory journey in the Sahelian region seems

to be the rule during both migratory seasons as implied by

our findings and past studies (Gschweng et al. 2008). Based

on our satellite data, Chad and Central African Republic

are added for the first time to the list of known staging

areas for the species. These observations are rather

important, given that records of Eleonora’s Falcons from

these countries were lacking up to the first published

telemetry data for the species (Gschweng et al. 2008).

Interestingly, one of the two juveniles stopped again for

a couple of weeks in Mozambique, before crossing the

Mozambique Channel, similar to an adult falcon from Italy

(Gschweng et al. 2008). Further data are needed to test

whether the interruption of its southward journey before

crossing the Mozambique Channel for the second time was

due to extreme or unfavourable weather conditions

(McGrady et al. 2006) or to favourable foraging opportu-

nities given the relatively high precipitation rate during

November and December in the area. In the latter case,

Mozambique could be considered part of the wintering

range of the species, as also implied by Gschweng et al.

(2008).

Migration speed in relation to latitude, sun, wind

and season

The migration speed of the four falcons in our study was

found to be influenced by the time of the day and the

combined effect of latitude and migratory season. Eleo-

nora’s Falcon, which is a slender-winged bird, has been

mainly observed flapping, although soaring is also common

close to the colony when updrafts are present (Hedenstrom

et al. 1999). In flapping birds, speed is expected to vary

both spatially and temporally, as a response to refuelling

needs in combination with the varying environmental

conditions encountered en route (Newton 2008). The

apparent independence of speed variation on wind could be

attributed to the coarse resolution of the available wind

data and/or to the selected pressure levels. In addition,

given the small sample size used in the analysis, our

findings should rather serve as an indication of the under-

lying causes for the observed patterns.

According to a recent study, there is evidence that

Eleonora’s Falcons select favourable wind conditions in

order to cross open water and, consequently, attain greater

airspeeds (Mellone et al. 2010). Yet, if wind assistance is

more crucial during sea crossings, as suggested by the

authors, then it is possible that the effect of wind becomes

non-statistically significant when considering the overall

migratory journey; hence, satellite tracking of more indi-

viduals in combination with meteorological data of finer

resolution could shed more light into this aspect.

846 J Ornithol (2012) 153:839–848

123

Moreover, our results suggest that the Sahara Desert and

Mozambique Channel are both considered barriers for

Eleonora’s Falcons since the four tracked birds substan-

tially increased their speed during both migratory periods.

The middle latitudinal bands, where the overall speed rate

was minimised, consist of areas where the birds spent a

considerable amount of time to rest and/or feed, as also

implied by the prolonged stopover of the juveniles in this

and previous studies (Gschweng et al. 2008; Lopez-Lopez

et al. 2010). It has been suggested that during autumn

Eleonora’s Falcons slowed down after crossing the Sahara

Desert, in order to counterbalance the energetic cost of a

non-stop flight of more than 1,000 km across this xeric

environment (Lopez-Lopez et al. 2010). This hypothesis

could also hold true for spring migration, as the birds in our

study reduced their speed substantially in the Sahelian

region, probably to replenish their fat reserves before

crossing desert landscapes.

Wintering period

Prior to the advent of satellite telemetry studies, on several

occasions groups or pairs of Eleonora’s Falcons have been

recorded in Madagascar from October to May (Milon et al.

1973; Walter 1979; Meyburg and Langrand 1985; references

in Ristow and Wink 1992–1994; Watson et al. 2005), yet of

unknown origin. In spite of the considerable number of

ringed juveniles, to our knowledge only five Eleonora’s

Falcons originating from Greece have ever been recovered in

Madagascar (from September to January; Ristow and Wink

1992–1994). All four falcons in our study headed to Mada-

gascar for wintering, while according to the two recent

satellite-tracking studies, 88% of the falcons from Italy and

Spain also overwintered there (Gschweng et al. 2008;

Lopez-Lopez et al. 2010). Until recently, due to the political

instability and the physiography of the country, the known

wintering distribution of the species was based on sporadic

field observations (Zefania 2001). For the first time, we were

able to follow up the quasi-daily schedule of four Eleonora’s

Falcons originating from Greece and, thus, corrobate pre-

vious findings. In agreement with past studies (Zefania 2001;

Gschweng et al., submitted), the four falcons remained in the

northern, mainly north-eastern, part of Madagascar. None-

theless, in contrast to previous findings (Meyburg and Lan-

grand 1985; Zefania 2001), our results indicate a statistically

significant preference towards submontane forests. A time-

series of processed satellite images representing the forested

areas in eastern Madagascar prior to human colonisation

until the mid-1980s revealed dramatic rates of forest loss

(Green and Sussman 1990). Since then, the rate of defores-

tation in the humid forest has slowed down (Conservation

International et al. 2007), yet forest fragmentation still

remains a challenge (Harper et al. 2007). Thus, future

degradation of the primary forest could constitute an

important threat to the species. Moreover, although some

parts of the estimated home ranges overlapped, the UDOI

metric is indicative of inter-individual variability in space

use. Thus, we believe that future studies focusing on habitat

use as a response to the temporal variability in tropical

wintering areas (Gschweng et al., submitted), as well as

considering more individuals of different breeding origin

could clarify key aspects of the wintering ecology of Eleo-

nora’s Falcon at the population or even at the species level.

Acknowledgments We would like to thank Evanthia Thanou for

conducting the molecular analyses for sex determination. We also

wish to express our gratitude to the local church authority for giving

permission to make use of the church building during the tagging of

the falcons and to Olga Karagianni for mediating the arrangements.

We also thank Fernando Spina, Italy, as well as an anonymous referee

for their fruitful comments on a previous version of this manuscript.

The work was funded by the A.G. Leventis Foundation through

project ‘‘Survey and Conservation of Seabirds in Greece’’. All

experiments and observations made for this study comply with current

laws of Greece.

References

Argos (2008) User’s manual. Toulouse, CLS/France

Calenge C (2006) The package adehabitat for the R software: a tool

for the analysis of space and habitat use by animals. Ecol Model

197:516–519

Conservation International, International Resources Group, Ministere

de l’Environnement des Eaux et Forets, United States Agency

for International Development (2007) Change in natural forest

cover Madagascar 1990–2000–2005. Conservation International,

Washington, DC

Cumming GS, Bernard RTF (1997) Rainfall, food abundance and

timing of parturition in African bats. Oecologia 111:309–317

Delgado G, Quilis V (1990) New data concerning the migration of

Eleonora’s falcon (Falco eleonorae). Ring Migr 11:111–112

Dimalexis A, Xirouchakis S, Portolou D, Latsoudis P, Karris G, Fric

J, Georgiakakis P, Barboutis C, Bourdakis S, Ivovic M et al

(2008) The status of Eleonora’s falcon (Falco eleonorae) in

Greece. J Ornithol 149:23–30

ESRI (2006) ArcGIS Desktop for Windows. Version 9.2. Redlands, CA

Fieberg J, Kochanny CO (2005) Quantifying home-range overlap: the

importance of the utilization distribution. J Wildl Manag

69:1346–1359

Fridolfsson A-K, Ellegren H (1999) A simple and universal method

for molecular sexing of non-ratite birds. J Avian Biol 30:

116–121

Green GM, Sussman RW (1990) Deforestation history of the eastern

rain forests of Madagascar from satellite images. Science

248:212–215

Gschweng M, Kalko EKV, Querner U, Fielder W, Berthold P (2008)

All across Africa: highly individual migration routes of Eleono-

ra’s falcon. Proc R Soc Lond B 275:2887–2897

Harper GJ, Steininger MK, Tucker CJ, Juhn D, Hawkins F (2007)

Fifty years of deforestation and forest fragmentation in Mada-

gascar. Environ Conserv 34:325–333

Hedenstrom A, Rosen M, Akesson S, Spina F (1999) Flight

performance during hunting excursions in Eleonora’s falcon

Falco eleonorae. J Exp Biol 202:2029–2039

J Ornithol (2012) 153:839–848 847

123

Helbig AJ (1996) Genetic basis, mode of inheritance and evolutionary

changes of migratory directions in Palearctic warblers (Aves:

Sylviidae). J Exp Biol 199:49–55

Janzen DH, Schoener TW (1968) Differences in insect abundance and

diversity between wetter and drier sites during a tropical dry

season. Ecology 49:96–110

Lopez-Lopez P, Liminana R, Mellone U, Urios V (2010) From the

Mediterranean Sea to Madagascar: are there ecological barriers

for the long-distance migrant Eleonora’s falcon? Landsc Ecol

25:803–813

McGrady MJ, Young GS, Seegar WS (2006) Migration of a peregrine

falcon Falco peregrinus over water in the vicinity of a hurricane.

Ring Migr 23:80–84

Mellone U, Lopez-Lopez P, Liminana R, Urios V (2010) Weather

conditions promote route flexibility during open sea crossing in a

long-distance migratory raptor. Int J Biometeorol 55(4):463–468

Meyburg B-U, Langrand O (1985) Evolution, Verbreitung und Status

der Greifvogel (Falconiformes) Madagaskars. In: Proceedings of

international symposium on African vertebrates, systematics,

phylogeny, Bonn, pp 193–205

Milon P, Petter J-J, Randrianasolo G (1973) Faune de Madagascar

XXXV: Oiseaux. Orstom and CNRS, Tanarive & Paris

Newton I (2008) The migration ecology of birds. Academic, London

Poulin B, Lefebvre G, McNeil R (1992) Tropical avian phenology in

relation to abundance and exploitation of food resources.

Ecology 73:2295–2309

R Development Core Team (2009) R: a language and environment for

statistical computing. R Foundation for Statistical Computing,

Vienna, Austria. ISBN 3-900051-07-0. http://www.R-project.org

Ristow D (1975) Neue ringfunde vom Eleonorefalken (Falcoeleonorae). Vogelwarte 28:150–153

Ristow D (2010) Up-date on breeding status and review on Eleonora’s

falcon Falco eleonorae when away from the breeding sites.

Il-Merill 32:1–5

Ristow D, Wink M (1992–1994) Distribution of non-breeding

Eleonora’s falcon (Falco eleonorae). Il-Merill 28:1–10

SPSS (2009) SPSS Base 18.0 for Windows User’s Guide. SPSS,

Chicago

Stresemann E (1954) Zur Frage der Wanderungen des Eleonorenfal-

ken. Vogelwarte 17:182–183

Thorup K, Alerstam T, Hake M, Kjellen N (2003) Can vector

summation describe the orientation system of juvenile ospreys

and honey buzzards?—An analysis of ring recoveries and

satellite tracking. Oikos 103:350–359

Walter H (1979) Eleonora’s falcon: adaptations to prey and habitat in

a social raptor. University of Chicago Press, Chicago

Wang LC, Chen CT, Lee HY, Lir JL, Chin SC, Pu CE, Wang CH

(2007) Sexing a wider range of avian species based on two

CHD1 introns with a unified reaction condition. Zoo Biol

26:425–431

Watson JEM, Whittaker RJ, Dawson TP (2005) The importance of

littoral forest remnants for indigenous bird conservation in

southeastern Madagascar. Biodivers Conserv 14:523–545

Zefania S (2001) Observation of Sooty and Eleonora’s Falcons in

Madagascar. In: Wings over Africa, Proceedings of International

seminar on bird migration: research, conservation, education and

flight safety, Israel, pp 151–159

848 J Ornithol (2012) 153:839–848

123