Trends in Abundance of Migrating Raptors at Gibraltar in Spring

Bensusan, Keith J.; Garcia, Ernest; Cortés, John E.

doi:10.5253/078.095.0109

Cited by 25 publications

(33 citation statements)

References 8 publications

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“…Considering they are the most numerous soaring migrant in the Afro‐Palearctic flyways (Shirihai et al . ; Bensusan, Garcia & Cortes ; Verhelst, Jansen & Vansteelant ) young, inexperienced honey buzzards are likely to encounter experienced conspecifics moving westwards shortly upon leaving the wintering grounds.…”

Section: Discussionmentioning

confidence: 99%

Seasonal detours by soaring migrants shaped by wind regimes along the East Atlantic Flyway

Vansteelant

Shamoun‐Baranes

Manen³

et al. 2016

Journal of Animal Ecology

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Summary1. Avian migrants often make substantial detours between their seasonal destinations. It is likely some species do this to make the most of predictable wind regimes along their respective flyways. We test this hypothesis by studying orientation behaviour of a long-distance soaring migrant in relation to prevailing winds along the East Atlantic Flyway. 2. We tracked 62 migratory journeys of 12 adult European Honey Buzzards Pernis apivorus with GPS loggers. Hourly fixes were annotated with local wind vectors from a global atmospheric model to determine orientation behaviours with respect to the buzzards' seasonal goal destinations. This enabled us to determine hot spots where buzzards overdrifted and overcompensated for side winds. We then determined whether winds along the buzzards' detours differed from winds prevailing elsewhere in the flyway. 3. Honey Buzzards cross western Africa using different routes in autumn and spring. In autumn, they overcompensated for westward winds to circumvent the Atlas Mountains on the eastern side and then overdrifted with south-westward winds while crossing the Sahara. In spring, however, they frequently overcompensated for eastward winds to initiate a westward detour at the start of their journey. They later overdrifted with side winds north-westward over the Sahel and north-eastward over the Sahara, avoiding adverse winds over the central Sahara. 4. We conclude that Honey Buzzards make seasonal detours to utilize more supportive winds further en route and thereby expend less energy while crossing the desert. Lifelong tracking studies will be helpful to elucidate how honey buzzards and other migrants learn complex routes to exploit atmospheric circulation patterns from local to synoptic scales.

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Section: Discussionmentioning

confidence: 99%

Seasonal detours by soaring migrants shaped by wind regimes along the East Atlantic Flyway

Vansteelant

Shamoun‐Baranes

Manen³

et al. 2016

Journal of Animal Ecology

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“…Hen Harriers are even less numerous at bottlenecks than Marsh Harriers: in spring, 3-84 were counted at the Strait of Messina (Corso 2001), negligible numbers at Eilat (Leshem & Yom-Tov 1998) and the Strait of Gibraltar (Bensusan et al 2007) and up to 250 at Falsterbo in autumn (Kjellén & Roos 2000). Considering only spring migration, the number of Hen Harriers migrating over the Medvedce reservoir is internationally important.…”

Section: Discussionmentioning

confidence: 99%

Spring migration of waterbirds and raptors at Medvedce reservoir (Dravsko polje, NE Slovenia)/ Spomladanska selitev vodnih ptic in ujed na zadrževalniku Medvedce (Dravsko polje, SV Slovenija)

Bordjan¹

2015

Acrocephalus

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Spring migration of birds, particularly waterbirds and raptors, was monitored from dawn till dusk from an observation point located on the levee on the northern side of the Medvedce reservoir (Dravsko polje, NE Slovenia) in three separate years (1-17 Mar 2009; 25 Mar-10 Apr 2011; 28 Feb-12 Apr 2012). In all three years, 42,045 individuals of 89 species (66 waterbirds, 23 raptors) migrated over the site. 38,238 of these were waterbirds. The most numerous species was Lapwing Vanellus vanellus (11,813 individuals), followed by Blackheaded Gull Chroicocephalus ridibundus (10,515 individuals). In total, 3807 migratory storks, raptors and Cranes Grus grus were counted. Harriers (2303 individuals) were by far the most numerous group. The prevailing direction of migration was SW-NE. Half of all migrating birds were observed in the altitudinal belt between 10 and 100 m above ground level. Harriers were mostly observed up to 100 m above ground level, whereas storks, other raptors and Cranes were observed most often in the altitudinal belt between 100 and 500 m above ground level. The highest numbers of waterbirds were observed between 10 and 100 m above ground level. In the first five hours after sunrise, 61.3% of all waterbirds, 44.0% of all storks and raptors and only 20.5% of Cranes were observed. Although other parts of Dravsko polje have never been studied in such detail, it is possible that a significant portion of migrating birds from a larger area gathers at this site. This study confirms the importance of the area for migrating and staging birds, especially for Great Egret Ardea alba, Marsh Circus aeruginosus and Hen Harriers C. cyaneus, Osprey Pandion haliaetus, Crane, Ruff Calidris pugnax and Black-headed Gull that all reached at least 0.1% of their respective biogeographic populations. Internationally significant are particularly the numbers of migrating Marsh (1079 individuals in 2012) and Hen Harriers (408 individuals in 2012), as there are only few sites where these species migrate in such high numbers in spring.

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“…Migration counts can even offer an alternative to breeding bird surveys for species that behave secretively or breed in remote parts of the world or inaccessible habitats. Thus, monitoring sites across the globe along major flyways for soaring birds were established in the 20 th century, and standardized migration counts have been used ever since to monitor migrant raptors across the globe (Bednarz et al 1990; Kjellen and Roos 2000; Shirihai et al 2000; McCarty and Bildstein 2005; Bensusan et al 2007; Farmer et al 2007; Filippi-Codaccioni et al 2010; Martín et al 2016). At the beginning of the 21 st century, new monitoring sites were established in important raptor migration flyways, such as those in Costa Rica and Panama along the Central American flyway (Porras-Peñaranda et al 2004; Batista et al 2005), Radar Hill and Khao Dinsor in Thailand (DeCandido et al 2004, 2008), and Thoolakharka in Nepal (DeCandido 2013).…”

Section: Introductionmentioning

confidence: 99%

Batumi Raptor Count: autumn raptor migration count data from the Batumi bottleneck, Republic of Georgia

Wehrmann¹,

Boer²,

Benjumea³

et al. 2019

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One of the most important geographical bottlenecks for migrating raptors in the east African-Palearctic migration system is situated between the easternmost tip of the Black Sea and the Lesser Caucasus, just north of Batumi, in the Republic of Georgia. Since 2008, citizen scientists of the Batumi Raptor Count (BRC) have monitored the autumn raptor passage daily from mid-August until mid-October, collecting also detailed information about the age and sex of focal species. The full BRC dataset was recently made available through the Global Biodiversity Information Facility (GBIF). Here we describe how count data were collected, managed, and processed for trend analysis over the past 10 years. This dataset offers a unique baseline for monitoring the state of migrant raptor populations in the east African-Palearctic flyway in the 21st century. We discuss potential pitfalls for users and hope that the open access publication of our data will stimulate flyway-scale and continent-wide collaboration for raptor migration monitoring in the Old World.

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Trends in Abundance of Migrating Raptors at Gibraltar in Spring

Abstract: BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

Cited by 25 publications

References 8 publications

Seasonal detours by soaring migrants shaped by wind regimes along the East Atlantic Flyway

Seasonal detours by soaring migrants shaped by wind regimes along the East Atlantic Flyway

Spring migration of waterbirds and raptors at Medvedce reservoir (Dravsko polje, NE Slovenia)/ Spomladanska selitev vodnih ptic in ujed na zadrževalniku Medvedce (Dravsko polje, SV Slovenija)

Batumi Raptor Count: autumn raptor migration count data from the Batumi bottleneck, Republic of Georgia

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