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Is the Slope Between the Alborz Mountains and Caspian Sea in Northern Iran a Bottleneck for Migrating Raptors?
... During autumn and spring, large numbers of migratory raptors pass along the major flyways, avoiding large water bodies or high mountain chains, and become concentrated at just a few bottleneck sites around the Mediterranean Sea, Black Sea and Red Sea ( Verhelst et al. 2011). The main bottleneck sites on the Western EuropeanWest African flyway are situated in Sweden, Spain, and Italy (Porter & Beaman 1985, Kjellén 1992, Kjellén & Roos 2000, Bildstein 2006, Polakowski et al. 2014), while those on the EurasianEast African flyway are in Romania, Bulgaria, Greece, Georgia, Turkey, and Israel (Porter and Beaman 1985, Shirihai & Christie 1992, Shirihai et al. 2000, Bildstein 2006, Ullman & Ullman 2010, Michev et al. 2011, Verhelst et al. 2011, Fülöp et al. 2018, Panuccio et al. 2018. ...
... The first follows both sides of the Black Sea and northern Caspian Sea area, bypassing the eastern Mediterranean Sea and the northern Red Sea, and move through Levant/Israel using the North Negev and Dead SeaKfar KasemEliatSuez route towards Sinai (Porter & Beaman 1985, Shirihai & Christie 1992, Shirihai et al. 2000, Verhelst et al. 2011, Fülöp et al. 2018). The second major route involves mostly the eastern and some western populations following the south eastern side of the Caspian Sea and crossing the north eastern Arabian Peninsula, the Arabian Gulf via the Hormuz Straits, and the southern Red Sea via the Bab elMandeb Straits between Yemen and Djibouti (Shiri- hai & Christie 1992, Shirihai et al. 2000, Ullman & Ull- man 2010, Panuccio et al. 2018). ...
... On the eastern Black Sea route, at the Batumi bottleneck in southwest Georgia, a total of 4234 marsh harriers were recorded between August and October in 2008-2009(Verhelst et al. 2011), a few of which may have drifted away on route to the Central Marshes. On the southern Caspian Sea route, at the Alborz Mountains in north eastern Iran, a total of 101 marsh harriers were recorded during autumn migration in October 2017 ( Panuccio et al. 2018). This route crosses the northern Arabian Gulf region on the way to eastern Africa, and seems to make a significant contribution to the Eurasian marsh harrier migratory/wintering population in the Central Marshes. ...
There is scarce information on the migration patterns and population size of the Eurasian marsh harrier ( Circus aeruginosus ) in Iraq in general and in the southern Mesopotamian wetlands in particular. From February 2018–April 2019, a total of 11 field expeditions were conducted in the Central Marshes (219,700 ha), one of the major Mesopotamian wetlands and Iraq’s National Park, a RAMSAR and UNESCO site. Two of the field survey objectives were to determine the spatial and temporal distribution and estimate the population size of the migratory/wintering Eurasian marsh harrier in the Central Marshes. Distance sampling on three line-transects covering a study plot of 40,000 ha was conducted. Among other wintering Circus harriers, the Eurasian marsh harrier was the most abundant species with a total of 93 individuals recorded. The estimated species densities were 0.0042–0.035 individuals/ha, and the estimated size of the Eurasian marsh harrier migratory population in the Central Marshes was 922.7–7689.5 individuals. Moreover, the migration phenology and breeding status of the Eurasian marsh harrier in the Central Marshes were investigated. Our efforts did not confirm the breeding of this species during recent years, or since the inundation of the Mesopotamian wetlands in 2003. Furthermore, hunting and trapping were identified as major threats affecting the species which need urgent conservation action.
... However, intermittent spring migration surveys may allow the detection of demographic and phenological changes in Palearctic raptor species. As migration survey and monitoring efforts continue to grow at known bottlenecks (Murgatroyd et al. 2021, Noby et al. 2022) and newly discovered sites (Panuccio et al. 2018, Jobson et al. 2021, and with new tracking studies underway, we can look forward to exciting discoveries on East African-Eurasian raptor migration in the near future. ...
... ,Verhelst et al. 2011) -albeit much higher numbers than were assumed to use this flyway. The seasonal passage at Batumi is also much greater than what has been recorded in other flyways around the Black and Caspian Sea in either season(Ullman & Ullman, 2010, Heiss 2013, Stanciu et al. 2017, Panuccio et al. 2018, and accounts for the vast majority of Steppe Buzzards entering the Middle East via Israel in spring (circa 300,000 individuals;Shirihai et al. 2000, Yosef et al. 2002. Black Kite is a species for which different authors have formulated contradicting expectations about spring flyway use(Shirihai et al. 2000, Abuladze 2013, Panuccio et al. 2014. ...
The extent to which geographical features like coastlines and mountain ranges funnel migrating birds depends on the seasonal context and direction of migration. Near Batumi, in the Republic of Georgia, the eastern Black Sea coast and Lesser Caucasus funnel over one million raptors through a 10-20 km wide coastal strip every autumn. The funnelling effect of the Lesser Caucasus appears much less evident for northbound migrants. Yet historical data suggest tens of thousands of raptors pass through the region in spring. To elucidate the composition and timing of spring raptor migration we conducted full-season migration surveys near Batumi in 2019, 2020 and 2022. In total, we recorded 33 species and, on average, counted 542,161 raptors (min. 455,799 - max. 618,848) annually. The bulk of the spring passage consisted of Black Kite Milvus migrans (239,649 +- 22,547) and Steppe Buzzard Buteo buteo vulpinus (194,029 +- 102,702). The most diverse and intense spring migration occurred from late March through mid-April, when the median passage date of 12 of 15 common species (>100 ind. y-1) occurred. Species with longer autumn migration periods tended to have longer spring migration periods, and most species had a longer migration period in spring than in autumn, likely due to larger age differences in timing during spring. Species abundance was up to an order of magnitude lower in spring than in autumn, consistent with a weaker bottleneck-effect in spring. Nevertheless, our results confirm the eastern Black Sea coast as a principal spring flyway and help redraw the map of East African-Eurasian migration for several Palearctic raptors. While we will not continue annual spring migration surveys, our data provides a baseline for detecting changes in raptor migration through short-term surveys and can help plan migration-based conservation and research at Batumi in spring.
... However, deep learning methods are required to distinguish between the different elements it detects and eliminate radar echoes that limit species differentiation (Schekler et al., 2023). In some cases, direct field observations are also needed to calibrate the information obtained (Panuccio, Ghafouri, & Nourani, 2018). ...
Wind farms are a clean and efficient source of renewable energy. However, they cause negative impacts on raptors. Here, we present a review of the existing scientific literature on the effects of wind farms on raptors' ecology with a particular interest in the potential solutions. After collecting 216 studies, we found a consensus in the literature that raptors exhibit avoidance behaviors, and that the abundance of raptors decreases after wind farm installation, although it might recover over time. The position of wind farms on mountaintop ridges poses a particular danger to large soaring raptors, as they rely on orographic uplift to gain altitude. Adult mortality significantly affects population dynamics, particularly in endangered species, but young inexperienced individuals show a higher collision risk. The combination of different methods including field monitoring, GPS telemetry and systematic search for carcasses is an adequate approach to further investigate the problem and solutions. Shutdowns on demand, the installation of deterrents, turbine micro‐sitting and the repowering of wind farms have been suggested as potential solutions, although results are contradictory and case‐specific. Furthermore, it is essential to report the potential occurrence of conflicts of interest in scientific papers, as they can influence the interpretation of the results. Finally, from a future perspective, it is crucial to assess the effectiveness of solutions to mitigate the negative effects of wind farms to promote raptor conservation. This becomes increasingly relevant in the context of renewable energy development and increasing energy demand worldwide.
... The main predicted connectivity path in the present study (yellow line in Fig. 6), has been identified as the main migration path between Asia and Africa in previous studies using satellite tracking (Meyburg et al., 2003;Katzner et al., 2022). A large number of Steppe Eagles choose this migration path, as indicated by the observation of 350 individuals at the corridor's northern terminus in Iran, southeast of the Caspian Sea, within a 25-h period in October 2017 (Panuccio et al., 2018). Another connectivity path extends from northeastern to southeastern Iran and from southeastern to southwestern Iran (green line in Fig. 6). ...
Understanding habitat suitability, the environmental variables limiting the distribution of species, and migratory paths are important issues for conservation of threatened bird species. Identifying areas important for birds and their overlap with conservation areas (CAs) can guide conservation managers in establishing new CAs. The Steppe Eagle (Aquila nipalensis) is a globally endangered winter visitor raptor in Iran. We used 164 occurrence records of Steppe Eagles and data on 12 environmental variables in Iran as input to ensemble modeling and electrical circuit theory models to identify, respectively, potential wintering areas and migratory paths between those wintering areas. Our results revealed that elevation, distance to rodents, mean diurnal range, distance to villages, and distance to cities were the most influential variables for habitat suit-ability in Iran. Potential wintering areas identified by our models were mainly located in the north and south of Iran and migratory paths connected these areas through the central plains. CAs covered about one-fifth of potential wintering areas. Conservation of the species within potential wintering areas and the migratory paths from northern to southern Iran is necessary for the survival of this endangered species in its entire distribution. Therefore, wildlife managers should pay increased attention to non-protected parts of potential wintering areas in order to establish new CAs and protect migration paths against threats. Our results pave the way for proper planning for the conservation of threatened raptors in Iran, particularly Steppe Eagle.
... To reach the Middle East during autumn, these birds that migrate from the eastern part of the western Palearctic use two main flyways: one that follows each side of the northern Caspian Sea and the Black Sea regions, avoiding the northern Red Sea and the eastern Mediterranean Sea, and one that moves across Palestine, taking the Dead Sea-Kfar Kasem-Eliat-Suez and North Negev pathways, reaching Sinai (Fülöp et al., 2018;Al-Sheikhly and Al-Azawi, 2019a). The second major route follows the southeastern part of the Caspian Sea, which crosses the north Arabian Peninsula and the Arabian Gulf through the Hormuz Straits and the southern Red Sea through the Bab El-Mandeb Straits between Djibouti and Yemen (Panuccio et al., 2018). ...
Monitoring migrating raptors is among the most cost-effective and simple methods for forecasting shift in the ecosystem and environment. The Western Marsh Harrier Circus aeruginosus (Linnaeus, 1758) (Accipitriformes, Accipitridae) represents a widely wintering, on-passage raptor over Iraq's southern Mesopotamian marshlands. However, recent information related to this species’ population trend, as well as its spatial and temporal migration patterns, is not fully known. From October 2021–June 2022, nine ornithological field surveys were undertaken in the Central Marshes (UNESCO Site, RAMSAR Site, and Iraq's National Park). Three transect lines were chosen, and the surveying plot covered 40,000 hectares (400 Km2). Our recent surveys recorded a total of 64 harriers passing over the Central Marshes. The species density was determined using a distance sampling method; perpendicular distances were gauged using a digital range finder. During our surveys, the Central Marshes hosted a migratory population of ≈3,508-21,499 harriers. In addition, we assessed the breeding status of this bird species in the surveyed area; however, no confirmed breeding was found. Furthermore, illegal hunting/trapping were identified as the main threat facing the species in Iraq.
... The second significant flyway includes primarily both the eastern and western populations that traveling along the southeast coast side of Caspian Sea and traversing the northern of the Arabian Peninsula , also Arabian Gulf and they use of Hormuz Straits, reach to southern Red Sea through the Straits of Bab-El-Mandeb among Yemen and Djibouti. (Shirihai and Christie, 1992;Shirihai et al., 2002;Ullman and Ullman, 2010;Panuccio, Ghafouri and Nourani, 2018). Many migrating raptors including but not limited to the Western Marsh Harrier pass through Iraq on their way to wintering sites in Arabia and Africa (Al-sheikhly and Al-azawi, 2019). ...
The current study gives information about the Taxonomy, morphology, and migration routes of the Western Marsh Harrier Circus aeruginosus which is one of the most common raptors in Iraq's southern Mesopotamian marshlands. This review presented several topics related to the monitoring migration of this bird, Western Marsh Harrier Circus aeruginosus, its classification where it belongs to the order of Accipitriformes and the family of Accipitridae. It has been considered a native breeding resident in Iraq marshes ( specially south area ) and maybe in the wetlands part of middle Iraq , also it has been considered a migrant visiting Iraq in winter. It was once widespread in the Euphrates wetlands, and It bred in Hammar Lake and the marshes nearby Basra. The description of the bird, is a huge, hefty harrier with rather broad wings, larger than other European harriers. The male's feathers is mysterious reddishbrown and brighter golden streaks seen especially over the breast. A majority of the area around the shoulders and the head have a mild greyish-yellowish color. The rectrices, secondary and tertiary remiges are all absolute grey, contrasting with a brown color in the forewing and the black main remiges on their wingtips. About the female is nearly totally chocolatey brown. The upper parts of the head, throat, and the shoulders have a markedly brighter yellowish tone; These could be sharply delineated with quite contrasting. There are two major known migratory raptor routes in the western Palearctic, the first one is flyway from West African , Eurasian- to East African (named western of Black Sea), that connects northern Europe with western Siberia to Middle East which ends in the sub-Saharan Africa ,the second flyway from Western European- to the West African ( the Atlantic) , which raptors use.
On the basis of data obtained from ARGOS/GPS and GPS/GSM tracking of 34 eagles (4 Steppe Eagles (Aquila nipalensis) from Central KZ, 1 Steppe Eagle from Southern Ural region, 22 Steppe Eagles, 5 Eastern Imperial Eagles (Aquila heliaca) from the ASR and 2 Greater Spotted Eagles (Aquila clanga) from the from the Altai-Sayan Ecoregion), we have defined the main flyways, terms, and other parameters of migration of eagles through Eastern Kazakhstan. We have outlined the borders of the migration corridor and estimate the number of migrants passing through it. The study highlights the importance of the Karatau ridge for eagles from the vast territories of Russia and Kazakhstan. But we are also concerned about the development of wind farms with horizontal-axis wind turbines that expose ultimate danger for raptors in the Karatau migration corridor. One of them already exists – the Zhanatas Wind-Power Station. Here we calculated the possible negative impact on the eagle population from the existing and projected wind farms of the Karatau ridge and give our recommendations for neutralizing the damage from the development of the electric power industry in Karatau.
The greater spotted eagle (Clanga clanga) is poorly known compared to other European eagles. We tracked an immature greater spotted eagle during 2018–2020 within the eastern European part of the species’ distribution, west of the Ural Mountains. Because so little is published about the annual movements of this species, especially from that region, tracking data from this single individual are valuable. 95% kernel density estimator (KDE) range sizes for the two complete winters in Yemen were 4,009 km2 (2018), 1,889 km2 (2019); 95% dynamic Brownian bridge movement models (dBBMM) encompassed 1,309 km2 (2018) and 1,517 km2 (2019). It returned to the same wintering area every year. During summer 2018, it settled into a small area (95% KDE = 126 km2; 95% dBBMM = 21 km2) near Birsk, eastern European Russia; in 2019 it wandered over a huge area (95% dBBMM = 66,304 km2) of western Kazakhstan and southern Russia, south west of Yekaterinburg. Spring migration 2018 was west of the Caspian Sea; during 2019 it was east of it. Mean speed of spring migration was 160±120 km/day during 2018, and 132±109 km/day during 2019. Autumn migration passed east of the Caspian in both years, and the mean speed of migration was 62 ± 78 km/day in 2018, and 84 ± 95 km/day in 2019. During both spring and autumn migrations, the eagle made stopovers, mostly lasting 1–2 days. The eastern Alborz Mountains in northeastern Iran appeared to be an important stopover locale, where autumn stopovers lasted 19 days (2018) and 27 days (2019). These and other data suggest that most greater spotted eagles that spend summers west of about 42°E, winter in southern Europe, Asian Turkey, the Levant and Africa, and those that summer to the east of that meridian winter in southern Asia, including Arabia.
Migration monitoring may allow us to detect population trends over large geographic areas because the pattern of change in migrant counts may be expected to follow the pattern of change in population size. We analysed recent regional European population trends of migratory soaring birds from rates of change in migration counts over the Strait of Gibraltar (Spain) during the years (1999–2013). An additional bottleneck (Organbidexka, France) within the same migratory route and period was also considered. We estimated count trends by fitting a log-generalized linear model to the time series of each species counts. The counts in Organbidexka were used to test the consistency in the observed trends over the Strait of Gibraltar. Migration counts of White and Black Storks, Black Kites, Short-toed and Booted Eagles as well as Egyptian Vultures showed a linear increase over the Strait of Gibraltar throughout the 15-year period. In contrast, Honey Buzzard numbers remained stable. Trends were highly consistent with those recorded in Organbidexka. We suggest that the larger slopes for the trends in Organbidexka when compared with the Strait reflect an increasing tendency in these species to overwinter in southern Europe. A combination of complementary data sets collected at different bottleneck sites within the European–African flyway system may become a fundamental tool for the investigation of migratory patterns and population trends and changes of soaring migrant birds all over Europe.
The study area at Zait Bay, Egypt (c. 700 km2) is situated in the middle of the West Asian-East African migration flyway used by very large numbers of soaring migrants. At this site the corridor narrows into a bottleneck. There exist only very few bottlenecks of this magnitude in the world. Observations were performed at all hours between sunrise and sunset at 26 observation sites, situated 5 km apart. The northern part of the area under investigation (19 observation sites) was situated within the Gebel El Zeit IBA (criteria A1 and A4iv), while the southernmost part (8 observation sites) was outside. The overall evaluation has shown that 179,681 soaring birds including 122,454 storks and 36,976 raptors were observed in total. Within a radius of 2.5 km from each observation site 97,143 soaring birds including 59,308 storks and 30,489 raptors were observed during the 604 hours of observation. Eleven species were recorded in numbers that exceed 1% of their flyway populations. Of special concern regarding bird conservation are those birds resting or flying in the first 200 m of elevation. In total 6,624 soaring birds were seen resting (2,252 within a radius of 2.5 km). Thirty-three percent of the storks and 47% of the raptors were observed resting or flying at heights within the lowest 200 m. The median height of flying birds varied between 5 m (harriers) and 500 m (Common Crane Grus grus). According to the raw data, criteria for nomination of the area as an IBA (20,000 raptors and storks in one migration season, globally threatened species) were fully met outside the existing IBA. Also, to the south of the study area, very high numbers of migrants were confirmed by spontaneous, non-systematic observations. Accordingly, a change of the boundaries is suggested. The regional analysis, based on extrapolations, has to be regarded as a preliminary study. The analysis failed to show a geographical trend for any single species. The data from this study establish a high concentration of gliding and soaring birds in the study area, within and adjacent to the already designated IBA.
Results of the first spring migration count of soaring birds at Ayn Sokhna, 60 km south of Suez on the west coast of the gulf of Suez, are presented. Significant numbers of raptors can be observed from this one observation site throughout the migration season regardless of each day’s wind direction and speed. Observations were recorded 5 hours daily 1 March–2 May 2012. A total of 183 275 migratory soaring birds were identified and counted, of which 154 276 were raptors (18 985 eagles), and
28 999 were storks, pelicans and cranes.
The timing of the passage of the following species was documented: Black Stork Ciconia nigra, White Stork Ciconia ciconia, European Honey Buzzard Pernis apivorus, Egyptian Vulture Neophron
percnopterus, Short-toed Snake Eagle Circaetus gallicus, Eurasian Sparrowhawk Accipiter nisus, Steppe Buzzard Buteo b. vulpinus,
Long-legged Buzzard Buteo rufinus, lesser Spotted Eagle Aquila pomarina, Steppe Eagle Aquila nipalensis and Booted Eagle
Aquila pennata. Totals and timing are compared to results of the study done in the Suez area 30 years ago.
Sixteen Steppe Eagles Aquila nipalensis were fitted with satellite transmitters during migration or on their wintering grounds (15 in Saudi Arabia, one in South Africa). From these 16 birds, a total of 3,734 location co-ordinates were received. Adult and immature Steppe Eagle migration strategies were markedly different in terms of timing (adults returned to breeding territories in southern Russia and Kazakhstan in late March and early April, whereas immatures arrived in mid May) but not in terms of route and wintering area. Immatures remained on the wintering grounds for substantially longer than adults, typically for about six months. An adult took almost eight weeks to cover 9,543 km from Botswana to Kazakhstan, averaging 177 km daily. The longest mean daily flight distance among all tracked individuals was approximately 355 km. In 1998, an adult male was recorded through a complete annual cycle; it spent 31.5% of the period in the wintering area in Ethiopia and Sudan, 41.9% in the breeding area in Kazakhstan, and 26.6% on migration.
Using a new survey station network we report the highest number of migrating raptors and Black Storks ever recorded on Bosporus during the autumn migration period. Also, we show that migration occurs with similar intensities over the full length of the strait, but individual migration patterns differ for some species at a local scale.
The short-toed snake eagle (Circaetus gallicus) uses mostly soaring flight over land during migration to avoid long sea crossings. In particular, birds breeding in central Italy cross the Mediterranean Sea at the Strait of Gibraltar, using a route through northwestern Italy during both autumn and spring migration. Birds breeding in Greece, such as those breeding in Italy, are expected to use the same strategy passing through northeastern Greece and avoiding the longer sea crossing between southern Greece and Libya. In order to verify this hypothesis, contemporaneous observations were made at two watchsites, in northwestern Italy (Apuane Alps) and northeastern Greece (Mount Olympus), during autumn 2009 and spring 2010. During autumn migration 376 birds were seen migrating at Mount Olympus, nearly all heading NNE. Most birds were seen migrating in flocks, and at least 23 flocks contained both adults and juveniles. Over the Apuane Alps a total of 1042 short-toed snake eagles, all migrating NNW, was counted. At this watchsite the proportion of juveniles was lower than that reported at Mount Olympus. During spring migration, 606 birds were seen at Mount Olympus, 602 heading south. At the Apuane Alps 1307 birds were counted, all heading SSE. The orientation behaviour of short-toed snake eagles confirms that those breeding in Greece, like those breeding in central Italy, use a circuitous route during both spring and autumn. In particular those breeding in Greece are expected to cross the sea at the Dardanelles and/or at the Bosphorus. In addition, the higher proportion of juveniles reported at Mount Olympus during autumn migration would suggest that social learning could have been much favoured by natural selection in the case of birds breeding in Greece rather than in Italy, highlighting a relationship between the length of the barrier and the tendency of juveniles to follow the adults.
Counts of migrating raptors at Batumi, Georgia, revealed the eastern Black Sea coast to form one of the most important bottlenecks for raptor migration during autumn in the Eurasian-African migration system. Totals for 10 species (European Honey-buzzard Pernis apivorus, Steppe Buzzard Buteo buteo vulpinus, Black Kite Milvus migrans, Eurasian Sparrowhawk Accipiter nisus, Levant Sparrowhawk Accipiter brevipes, Montagu's Harrier Circus pygargus, Pallid Harrier Circus macrourus, Lesser Spotted Eagle Aquila pomarina, Greater Spotted Eagle Aquila clanga, Booted Eagle Aquila pennata) exceeded 1% of their estimated world population. We compare the observed abundance of each species to estimates of the presumed source populations in European Russia. Counts of most species involved only a limited subset of these source populations, except for European Honey-buzzard and Lesser Spotted Eagle, which were more numerous than predicted. This could be due to inaccurate population estimates or because birds from NE Europe or W Asia are also using this migration route.
Migratory flights of Marsh Harriers (Circus aeruginosus), Montagu' s Harriers (Circus pygargus) and Pallid Harriers (Circus macrourus) in southern Israel were used to test flight theory predictions. The body sizes of these closely related species are between those of the typical large soaring migrants, such as eagles and storks, and the typical flapping migrants, such as small falcons and sparrowhawks. In soaring-gliding flight, Marsh Harriers reacted to different thermal conditions by adjusting their gliding airspeed to the actual climbing rate in thermal circling; consequently, cross-country speed was related to climbing rate. In contrast, the smaller Montagu' s and Pallid Harriers did not adopt gliding airspeeds according to thermal conditions. All harrier species regularly used flapping-gliding flight, predominately soon after sunrise and before sunset, and more often in opposing winds than in following winds. Montagu' s/Pallid Harriers used flapping-gliding more frequently than Marsh Harriers. Because they alternate between different flight styles, harriers are more independent of environmental factors, such as thermal activity and wind, compared to pure soaring migrants. This allows harriers to migrate under unfavorable thermal and wind con-ditions. Marsh Harriers are similar to typical soaring migrants in maximizing cross-country speed in soaring-gliding flight, whereas Montagu' s and Pallid Harriers are less adapted to soaring-gliding flight and thus are similar to smaller flapping migrants. Optimal soaring-gliding flight seems to be less relevant for these smaller harriers; they maximize cross-country performance by efficiently combining different flight styles.
The comparison of flight styles and flight parameters of migrating raptors in Israel revealed the following. (1) Climbing rate in thermal circling did not differ between species, indicating that chiefly the strength of thermal updrafts determined the climbing rate and that morphological features were less relevant. (2) In interthermal gliding, air speed was positively and gliding angle negatively related to the species' average body mass. Heavier species glided faster and had smaller gliding angles. (3) In soaring and gliding flight, cross-country speed relative to the air was positively related to the species' body mass; it was obviously the result of the gliding ability increasing with body mass. (4) Eagles and buzzards used soaring and gliding flight for more than 95% of the observation time. Additional soaring in a straight line whilst gliding was extensively used by the Steppe Eagle Aquila nipalensis, Lesser Spotted Eagle Aquila pomarina and Booted Eagle Hieraætus pennatus and even more frequently by the resident species, the Griffon Vulture Gyps fulvus and Shorttoed Eagle Circaetus gallicus. Smaller species, such as the Levant Sparrowhawk Accipiter brevipes, harriers (Circus sp.) and small falcons (Falco sp.). showed the highest proportion of flapping and gliding flight (9–33%). (5) In a comparison of the flight parameters and proportions of flight styles, a cluster analysis distinguished two main groups: The first consisted of Montagu's Harrier Circus pygargus, Pallid Harrier Circus macrourus, Levant Sparrowhawk and small falcons; their flight behaviour was characterized by both the high proportion of flapping and the low gliding performance. The second group comprised the typical soaring migrants: Steppe Eagle, Lesser Spotted Eagle, Booted Eagle, Steppe Buzzard Buteo buteo vulpinus, Honey Buzzard Pernis apivorus and Egyptian Vulture Neophron percnopterus, and they had very similar flight behaviour and were closely clustered. The Black Kite Milvus migrans and Marsh Harrier Circus aeruginosus were intermediate between typical soarers and flappers. The two resident species, Griffon Vulture and Short-toed Eagle, were grouped separately from the soaring migrants.
Afro-Palearctic migrants move between breeding and wintering grounds along flyways determined by several factors (bird morphology, geography, behavioural adaptations) and raptors often concentrate at straits to avoid long sea crossings. Here we test the hypothesis that raptor passages across different areas of the Turkish straits are similar in species composition as well as flight behaviour. We made simultaneous observations at the bosphorus and at the Dardanelles in autumn 2010. We tested the influence of weather, time of day and flock size on the intensity and spatial shift of migratory flow as well as the tendency to cross the Dardanelles Strait rather than follow the peninsula. we also collected information of the flight altitude of raptors using an optical range finder. The species composition observed at the two sites was completely different, with eagles predominating at the bosphorus and small and medium-sized raptors predominating at the Dardanelles Strait. Compensation for wind drift at the bosphorus was species-specific, with small and medium-sized raptors showing a drift effect by crosswinds, and eagles showing compensation and overcompensation. Mean flight altitude was similar among species, while the response to weather conditions varied, being mainly affected by wind. In the case of Short-toed Snake-eagles, flight ability and response to weather conditions was also agedependent. These results show that the flight strategies of migrating raptors are species-specific even if some flight parameters may converge as a result of risk minimisation. The differences between species and flyways probably reflect interspecific differences in the ability to fly over water.
Key words: bosphorus, Dardanelles Strait, raptor migration, Turkey, weather.
Migratory raptors rarely fly over stretches of water larger than 25 km, although different species undertake water crossings of varying lengths, depending mainly on their wing morphology. Oriental Honey-buzzards fly c. 680 km over the East China Sea in autumn from breeding areas in Japan to wintering areas in Southeast Asia, but avoid this long water crossing in spring. We investigated the effects of weather on this exceptional migratory behaviour and its seasonality through a maximum entropy niche modelling approach. We used data collected through satellite tracking of 31 adult birds as presence points and a set of variables related to wind, precipitation and convective condition as environmental predictors. Results of modelling showed very different, almost non-overlapping, areas suitable for migration over the East China Sea region in autumn and spring. Suitable migration routes in autumn mostly occurred over the sea, whereas suitable areas for spring migration mostly occurred over land, suggesting that circumnavigating the East China Sea is preferable in spring. At the regional scale, wind conditions facilitate water-crossing behaviour of Oriental Honey-buzzards in autumn, but not in spring. Specifically, suitable tailwinds over the sea enable water-crossing in autumn, whereas in spring, wind support and convective conditions are best over land. Our modelling did not suggest any importance of convective conditions for autumn migration. However, we expect that at smaller temporal scales, convective conditions would be a considerable facilitator of the water-crossing behaviour in this species.
Resumen.—Se contaron las rapaces migratorias en el estrecho de Messina, el cruce sobre el agua más angosto ubicado entre Sicilia e Italia continental, con el objetivo de investigar la influencia de la dirección y la velocidad del viento sobre el comportamiento de las rapaces que cruzan el estrecho. El estudio fue realizado en la primavera, del 27 de marzo al 31 de mayo de 2004. Los mayores números de rapaces se observaron migrando en el estrecho en días con el viento en contra a la dirección de desplazamiento. La velocidad del viento no afectó el paso de la especie observada con mayor frecuencia, Pernis apivorus. Los resultados sugieren que las rapaces típicamente cruzan el mar en el punto más estrecho entre Sicilia y la península italiana cuando las condiciones no son propicias para cruzar un tramo más amplio sobre el agua. [Traducción del equipo editorial]
Bird migration routes often follow detours where passages across ecological barriers are reduced in extent. This occurs in spite of the fact that long barrier crossings are within the birds' potential flight range capacity. Long-distance flights are associated with extra energy costs for transport of the heavy fuel loads required. This paper explores how important the fuel transport costs, estimated on the basis of flight mechanics, may be to explain detours for birds migrating by flapping flight. Maximum detours in relation to expanse of the barrier are predicted for cases where birds travel along the detour by numerous short flights and small fuel reserves, divide the detour into a limited number of flight steps, and where a reduced barrier passage is included in the detour. The principles for determining the optimum route, often involving a shortcut across part of the barrier, are derived. Furthermore, the effects of differences in fuel deposition rates and in transport costs for the profitability of detours are briefly considered. An evaluation of a number of observed and potential detours in relation to the general predictions of maximum detours, indicates that reduction of fuel transport costs may well be a factor of widespread importance for the evolution of detours in bird migration at wide ecological barriers.
Central Mediterranean flyway: A 5-year study
Central Mediterranean flyway: A 5-year study. Avian
Research 8:24. https://doi.org/10.1186/s40657-017-0081-6.
Flight Strategies of Migrating Hawks
- P Kerlinger
Kerlinger, P. (1989). Flight Strategies of Migrating Hawks.
University of Chicago Press, Chicago, IL, USA.
An autumn movement of raptors at the south-east corner of the Caspian Sea
- M R W Rands
- C G R Bowden
- P N Newton
Rands, M. R. W., C. G. R. Bowden, and P. N. Newton (1982).
An autumn movement of raptors at the south-east
corner of the Caspian Sea. Ornithological Society of the
Middle East Bulletin 8:3.
Raptor Migration in Israel and the Middle East: A Summary of 30 Years of Field Research
- H Shirihai
- R Yosef
- D Alon
- G M Kirwan
- R Spaar
Shirihai, H., R. Yosef, D. Alon, G. M. Kirwan, and R. Spaar
(2000). Raptor Migration in Israel and the Middle East:
A Summary of 30 Years of Field Research. International
Birding and Research Center, Eilat, Israel.
The autumn migration of raptors and other soaring birds across the Bab-el-Mandeb Straits
- G Welch
- H Welch
Welch, G., and H. Welch (1988). The autumn migration of
raptors and other soaring birds across the Bab-el-Mandeb Straits. Sandgrouse 10:26-50.
Spring raptor observations from Djibouti
- G Welch
- H Welch
Welch, G., and H. Welch (1991). Spring raptor observations from Djibouti. Ornithological Society of the
Middle East Bulletin 26:25-27.
Raptor Watch: A Global Directory of Raptor Migration Sites
- J Zalles
- K Bildstein
Zalles, J., and K. Bildstein (2000). Raptor Watch: A Global
Directory of Raptor Migration Sites. BirdLife Conservation Series No. 9. BirdLife International, Cambridge,
UK, and Hawk Mountain Sanctuary Association, Kempton, PA, USA.