Raptor Migration Research Articles

Long-Term Phenological Shifts in Raptor Migration and Climate

Climate change is having a discernible effect on many biological and ecological processes. Among observed changes, modifications in bird phenology have been widely documented. However, most studies have interpreted phenological shifts as gradual biological adjustments in response to the alteration of the thermal regime. Here we analysed a long-term dataset (1980-2010) of short-distance migratory raptors in five European regions. We revealed that the responses of these birds to climate-induced changes in autumn temperatures are abrupt and synchronous at a continental scale. We found that when the temperatures increased, birds delayed their mean passage date of autumn migration. Such delay, in addition to an earlier spring migration, suggests that a significant warming may induce an extension of the breeding-area residence time of migratory raptors, which may eventually lead to residency.

When and where does mortality occur in migratory birds? Direct evidence from long‐term satellite tracking of raptors

Information about when and where animals die is important to understand population regulation. In migratory animals, mortality might occur not only during the stationary periods (e.g. breeding and wintering) but also during the migration seasons. However, the relative importance of population limiting factors during different periods of the year remains poorly understood, and previous studies mainly relied on indirect evidence. Here, we provide direct evidence about when and where migrants die by identifying cases of confirmed and probable deaths in three species of long-distance migratory raptors tracked by satellite telemetry. We show that mortality rate was about six times higher during migration seasons than during stationary periods. However, total mortality was surprisingly similar between periods, which can be explained by the fact that risky migration periods are shorter than safer stationary periods. Nevertheless, more than half of the annual mortality occurred during migration. We also found spatiotemporal patterns in mortality: spring mortality occurred mainly in Africa in association with the crossing of the Sahara desert, while most mortality during autumn took place in Europe. Our results strongly suggest that events during the migration seasons have an important impact on the population dynamics of long-distance migrants. We speculate that mortality during spring migration may account for short-term annual variation in survival and population sizes, while mortality during autumn migration may be more important for long-term population regulation (through density-dependent effects).

Ecological Specialization to Fluctuating Resources Prevents Long-Distance Migratory Raptors from Becoming Sedentary on Islands

BackgroundThe adaptive transition between behavioral strategies, such as the shift from migratoriness to sedentariness, remains an outstanding question in evolutionary ecology. Density-dependent variation in the age of first breeding has been proposed as a feasible mechanism through which long-lived migratory birds with deferred sexual maturity should become sedentary to persist on islands. Although this pattern seems to hold for most raptors and herons, a few exceptions have been identified. One of these exceptions is the Eleonora’s falcon, a long-distance migratory bird, which shows one of the most peculiar adaptations in the timing of reproduction and food requirements among raptors.Methodology/Principal FindingsHere, we compiled data concerning demography, banding recoveries and satellite tracking of Eleonora’s falcons to discuss likely explanations for the exceptional behavior of this insular long-distance migratory species.Conclusions/SignificanceNew data reveal that Eleonora’s falcons do return to the natal colonies in their first year and young birds are able to breed. However, in contrast to previous hypothesis, the highly specialized strategy of this and other ecologically similar species, as well as the virtual lack of food during winter at breeding areas prevent them from becoming sedentary on islands. Although the ultimate mechanisms underlying the process of sedentarization remain poorly understood, the evidence provided reveal the existence of important trade-offs associated with ecological specialization that may become particularly relevant in the present context of global change.

KARATERISTIK HABITAT MUSIM DINGIN SIKEP MADU ASIA (PERNIS PTYLORHYNCHUS) DI TALAGA BODAS, JAWA BARAT BERBASIS DATA SATELLITE TRACKING

ABSTRACT Oriental Honey Buzzards (OHBs, Pernis ptilorhynchus) are migratory raptors which have wintering grounds in Indonesia. OHBs’ wintering habitats can be divided into core and edge habitats with unique landscape characteristics, which influence wintering site selection.TalagaBodasandsurroundingareahas beenidentifiedas wintering habitat of OHB based satellite tracking data. Theobjective of this study were to: 1) modeling the distribution of wintering habitat of OHB in Talaga Bodas; 2) analyzemicro habitats of vegetationaspect inTalagaBodas; 3) implications of wintering habitatmanagement inWest Java. Main methodology was combining satellite-tracking data of OHB with the GIS/remote sensing datausing logistic regression model. 18 Environmental variable used in this study include nearest distance to the elevation (0-300m, 300-500m, 500-700m, 700-1000m, >1000m),slope (0-3%, 3-8%, 8-15%, 15-25%, 25-40%, >40%) and landcover (water body, paddy field,abandon land,settlement,shrub,plantation,forest). Only 7 variables were detected as important variable for characteririzing the distribution of wintering habitat. Wintering habitat distribution model werepredominantly influenced by 1) slope 25%-40%, 2) elevation 0-300 m, 3) elevation 300-500 m, 4) elevation >1000 m, 5) forest, 6) paddy field and 7) water body. The results of the vegetation analysis’s known that the core habitat biodiversity tend to have less variable than the edge habitats.The results ofthis studywillbe usedformanagement ofwinteringhabitat for OHB. Key words:logistic regression, oriental honey-buzzards, satellite tracking, talaga bodas, wintering habitat

A review on raptor migration and toxicological effects of heavy metals

Se expone la importancia de las rapaces migratorias y su uso como bio-indicadores para determinar la presencia y concentraciones de metales pesados y metaloides, se exhibe también un panorama general sobre los efectos toxicológicos. Cabe mencionar que actividades antrópicas como la minería, la petroquímica y la agricultura son una de las principales fuentes de emisión de contaminantes ambientales. Los efectos sobre la salud de las rapaces migratorias es variable y actualmente se realizan estudios para determinar los grados de afectación. Algunos metales pesados y metaloides tienen efectos negativos sobre biomoléculas importantes del metabolismo celular; a pesar de la cantidad de trabajos realizados, los resultados no son concluyentes y los cambios en las poblaciones naturales de las especies son diversos.

The Calabrian Apennines: Important Bird Area (IBA) for the Autumn migration of Raptors

Observations on the autumn migration of raptors were carried out on the Calabrian Appennines in the area where the Italian peninsula is only 30 km wide. We used three different watch points at the same time between 24 August and 12 September 2005 and 2006. We observed 4,842 raptors in 2005 and 5,324 in 2006; most of these were Honey Buzzards, Black Kites, Marsh Harriers and Montagu’s Harriers.

Spring raptor migration over the Aeolian Archipelago

Spring raptor migration observations were performed from the island of Panarea in the period 20/4-20/5 of the years 2004, 2005 and 2006. The highest numbers were recorded for the Honey Buzzard, but also other species such as Marsh Harrier, Black Kite and Montagu’s Harrier were observed.

Raptor Migration at Concepción, Bolivia

I conducted the second austral autumn raptor count at Concepción Watch Site in the eastern Bolivian lowlands to document species composition, timing, and abundance of migrating raptors between 10 March and 6 April 2009. I counted migrants for 26 days (134.5 hrs) recording 6,979 migrating raptors of 16 species. Mississippi Kites (Ictinia mississippiensis) comprised 80% (n = 5,571), Black Vultures 11% (Coragyps atratus, n = 747), and Snail Kites 5% (Rostrhamus sociabilis, n = 396). The remaining 4% (n = 265) included 13 species and other unidentified raptors. I also recorded non-raptor species on migration from the lookout, including 36 Maguari Storks (Ciconia maguari), a flock of 11 Anhinga (Anhinga anhinga), and thousands of Barn Swallows (Hirunda rustica). My observations confirm previous records suggesting a significant raptor migration occurs at the Concepción Watch Site in the austral autumn. Raptor monitoring should continue at Concepción annually and the site used to promote raptor conservation and awareness in Bolivia.

Determination of Raptor Migratory Patterns Over a Large Landscape

Abstract Each autumn, tens of thousands of raptors pass over Hawk Ridge in Duluth, Minnesota, on their southbound migration, but migratory pathways leading to Hawk Ridge are unknown. To address this issue, we counted migrating raptors between mid-August and mid-November 2008 from 24 observation points along eight transects perpendicular to the shoreline between Duluth and the Minnesota-Canadian border. Our goals were to determine migratory pathways over a large area (>2000 km2) and identify how these movements were affected by weather, time of day, season, and characteristics of the landscape. A total of 4303 raptors of 14 different species were counted during the 2008 migration season. Exploratory analyses suggested that migratory raptors concentrated near the northern shoreline of Lake Superior, particularly during midday when winds are westerly. Average migration height differed between soaring raptors (buteos and eagles) and accipiters, with >40% of soaring raptors observed higher than 100 m above the...

A long-term database on raptor migration at Hawk Mountain Sanctuary, northeastern United States

In most northern temperate regions diurnal birds of prey, or raptors, migrate seasonally between their breeding and wintering grounds. Although their populations can be logistically difficult to survey and monitor because the birds are largely secretive and wide-ranging, most raptors are obligate or facultative soaring migrants that congregate along major thermal and orographic updraft corridors during their seasonal movements. Hawk Mountain Sanctuary (41° N, 75° W), which straddles the Kittatinny Ridge, the southernmost ridge in the Appalachian Mountains in eastern Pennsylvania, witnesses large numbers of migrating raptors during autumn migration. The Sanctuary's long-term migration-count database is the oldest detailed archive on the timing and magnitude of migratory raptors in the world. Records comprise daily (1934–1965) or hourly (1966–present) counts of 18 North American species of raptors migrating past the Sanctuary, as well as detailed weather data recorded from the lookout during autumn migratio...

Topography drives migratory flight altitude of golden eagles: implications for on‐shore wind energy development

Summary Wind power is a fast‐growing industry with broad potential to impact volant wildlife. Flight altitude is a key determinant of the risk to wildlife from modern horizontal‐axis wind turbines, which typically have a rotor‐swept zone of 50–150 m above the ground. We used altitudinal GPS data collected from golden eagles Aquila chrysaetos tracked using satellite telemetry to evaluate the potential impacts of wind turbines on eagles and other raptors along migratory routes. Eagle movements during migration were classified as local (1–5 km h−1) or migratory (>10 km h−1) and were characterized based on the type of terrain over which each bird was flying, and the bird's distance from wind resources preferred for energy development. Birds engaged in local movements turned more frequently and flew at lower altitude than during active migration. This flight behaviour potentially exposes them to greater risk of collision with turbines than when engaged in longer‐distance movements. Eagles flew at relatively lower altitude over steep slopes and cliffs (sites where orographic lift can develop) than over flats and gentle slopes (sites where thermal lift is more likely). Eagles predominantly flew near to wind resources preferred by energy developers, and locally moving eagles flew closer to those wind resources with greater frequency than eagles in active migration. Synthesis and applications. Our research outlines the general effects of topography on raptor flight altitude and demonstrates how topography can interact with raptor migration behaviour to drive a potential human–wildlife conflict resulting from wind energy development. Management of risk to migratory species from industrial‐scale wind turbines should consider the behavioural differences between both locally moving and actively migrating individuals. Additionally, risk assessment for wind energy–wildlife interactions should incorporate the consequences of topography on the flight altitude of potentially impacted wildlife.

Testing an emerging paradigm in migration ecology shows surprising differences in efficiency between flight modes.

To maximize fitness, flying animals should maximize flight speed while minimizing energetic expenditure. Soaring speeds of large-bodied birds are determined by flight routes and tradeoffs between minimizing time and energetic costs. Large raptors migrating in eastern North America predominantly glide between thermals that provide lift or soar along slopes or ridgelines using orographic lift (slope soaring). It is usually assumed that slope soaring is faster than thermal gliding because forward progress is constant compared to interrupted progress when birds pause to regain altitude in thermals. We tested this slope-soaring hypothesis using high-frequency GPS-GSM telemetry devices to track golden eagles during northbound migration. In contrast to expectations, flight speed was slower when slope soaring and eagles also were diverted from their migratory path, incurring possible energetic costs and reducing speed of progress towards a migratory endpoint. When gliding between thermals, eagles stayed on track and fast gliding speeds compensated for lack of progress during thermal soaring. When thermals were not available, eagles minimized migration time, not energy, by choosing energetically expensive slope soaring instead of waiting for thermals to develop. Sites suited to slope soaring include ridges preferred for wind-energy generation, thus avian risk of collision with wind turbines is associated with evolutionary trade-offs required to maximize fitness of time-minimizing migratory raptors.

Differential Migration in Five Species of Raptors in Central Coastal California

Using data from 17 144 hawks trapped during migration through the Marin Headlands in central coastal California, we evaluated the extent of differential migration within five species of raptors and compared our findings to those obtained at other raptor-migration sites in North America. This is the first description of patterns of differential migration for raptors migrating along the Pacific corridor, and the first investigation of differential migration in Red-shouldered Hawks (Buteo lineatus). We found that females migrated significantly earlier than males in Cooper's Hawks (Accipiter cooperii), Sharp-shinned Hawks (Accipiter striatus), hatch-year (HY) American Kestrels (Falco sparverius), HY Merlins (Falco columbarius), and HY Red-shouldered Hawks. In American Kestrels we found no difference in migration timing between AHY females and males or between adults and juveniles overall. Juveniles preceded adults in Sharp-shinned Hawks and Cooper's Hawks. We did not have sufficient samples of adult Red-shouldered Hawks, or Merlins, to compare migration timing among age classes. For Cooper's Hawks, Sharp-shinned Hawks, American Kestrels, Merlins, and Red-shouldered Hawks, our data agreed with the patterns of migration seen elsewhere in North America. Our description of the migration patterns in Red-shouldered Hawks provides a baseline for future comparisons with data from other migration sites.Empleando datos de 17 144 halcones capturados durante la migración a lo largo de Marin Headlands en la costa central de California, evaluamos el alcance de la migración diferencial en cinco especies de rapaces y comparamos nuestros resultados con aquellos obtenidos en otros sitios migratorios de América del Norte. Esta es la primera descripción de patrones de migración diferencial para rapaces que migran a lo largo del corredor Pacífico y la primera investigación de migración diferencial en Buteo lineatus. Encontramos que las hembras migraron significativamente más temprano que los machos en Accipiter cooperii, y en A. striatus, y que los individuos del primer año de eclosión (PAE) de Falco sparverius, individuos del PAE de Falco columbarius e individuos del PAE de B. lineatus. En F. sparverius no encontramos diferencias en el momento de migración entre hembras y machos del PAE o entre adultos y juveniles. Los juveniles precedieron a los adultos en A. striatus y en A. cooperii. No tuvimos suficientes muestras de adultos de B. lineatus o de F. columbarius para comparar el momento de migración entre las clases de edad. Para A. cooperii, A. striatus, F. sparverius, F. columbarius y B. lineatus, nuestros datos concuerdan con los patrones de migración vistos en otros sitios en América del Norte. Nuestra descripción de los patrones de migración en B. lineatus brindan información de base para futuras comparaciones con datos de otros sitios migratorios.

Fidelity to Roost Sites and Diet Composition of Wintering Male Urban Common KestrelsFalco tinnunculus

Abstract. During harsh winters, partially migratory raptors face to making a decision whether leave their breeding sites or not. However, decision to leave brings advantages for maintaining own body condition, but also disadvantages for further reproduction. We studied individual variability in fidelity to roost sites during two winters. The kestrel males in Ceske Budějovice (Southern Bohemia) roost near their breeding sites for most of the winter. Individuals occupy the same roost site continuously, unless they temporarily leave the city. We collected pellets at the males' roost sites from November to April in 1996/1997 and 1997/1998. We analysed the factors that affect males' presence (proportion of days with snow cover — PSC, snow depth and mean temperature). There were fewer absences, overall, in 1997/1998 than in 1996/1997, probably due to milder weather conditions, and better prey availability. Individuals responded differently to periods of snow cover; some males left the city but others remained. ...

South West Georgia: An Important Bottleneck for Raptor Migration during Autumn

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 Birds: Ecology and Conservation. A report on the BOU’s Annual Conference held at the University of Leicester, 5–7 April 2011

In April 2011, the British Ornithologist’s Union’s annual conference took place at the University of Leicester. The theme of this year’s conference was the ecology and conservation of migratory birds, and talks ranged from those focussed on either breeding, migration or wintering ecology, to those linking two or more of these and trying to build a more complete picture of the complex problems faced by long distance migrants. Talks also covered recent technological advances, which are increasingly allowing us intriguing new insights, particularly into the seasonal movements and wintering areas of some of the most declining species. Finally, talks examined the policy challenges associated with protecting migratory species and how best to tackle flyway-scale conservation of migratory birds.

Assessing Avian-Wind Turbine Collision Risk: An Approach Angle Dependent Model

A site specific model of avian-turbine collision risk is an important component of assessing environmental impacts from wind power projects. Existing models assume, however, that avian flight paths are either parallel or perpendicular to the turbine orientation and that other orientations do not significantly affect the predicted collision probability. We describe a mathematical model which estimates the probability of a collision between a bird passing through a wind turbine and one of the turbine components. Our model improves significantly upon the reference “Tucker Model”, and Band model, by accounting for different angles of avian approach other than perpendicular or parallel to the turbine rotor plane. We demonstrate, using a case study of fall raptor migration data, that the angle of approach between the flight path and the turbine orientation has a significant effect on the collision probability and resulting mortality estimates. We conclude that the angle of approach should be considered when estimating avian-turbine collision risk.

Wind Effects on Visible Raptor Migration in Spring at the Strait of Messina, Southern Italy

EFECTOS DEL VIENTO SOBRE LA MIGRACION VISIBLE DE RAPACES EN LA PRIMAVERA EN EL ESTRECHO DE MESSINA, SUR DE ITALIA Resumen.—Se contaron las rapaces migratorias en el estrecho de Messina, el cruce sobre el agua mas angosto ubicado entre Sicilia e Italia continental, con el objetivo de investigar la influencia de la direccion 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 numeros de rapaces se observaron migrando en el estrecho en dias con el viento en contra a la direccion de desplazamiento. La velocidad del viento no afecto el paso de la especie observada con mayor frecuencia, Pernis apivorus. Los resultados sugieren que las rapaces tipicamente cruzan el mar en el punto mas estrecho entre Sicilia y la peninsula italiana cuando las condiciones no son propicias para cruzar un tramo mas amplio sobre el agua. [Traduccion del equipo editorial]

Yellowstone Raptor Initiative

During 2010, the Yellowstone Raptor Initiative (YRI) used grant funds from the NPS Research Station-Wyoming to create a program with a raptor-centric focus. This program, in its infancy, concentrated on involving park visitors and staff in obtaining and collating raptor sightings in Yellowstone National Park. The funds also helped locate what may be a significant raptor migration corridor through Hayden Valley, as noted via the documentation of concentrations of Swainson’s Hawks on their flight through Yellowstone National Park to Argentina. Park staff and visitors attended raptor ecology and identification programs presented during the summer and fall, while a pilot ranger-led hawkwatch in Hayden Valley attracted 160 attendees, including area residents, park staff and park visitors. The Yellowstone Raptor Initiative also conducted additional outreach by presenting technical papers at the Raptor Research Foundation annual meeting regarding the YRI, and scientific work which had been accomplished by the Initiative’s participating agencies and biologists during the 2010 funding year.

Vinculando a la comunidad en los conteos de aves rapaces migratorias (aves: falconiformes) en el este de Cuba

A través de entrevistas, talleres, charlas y encuentros socioculturales, se realiza la vinculación de tres comunidades de la zona alta de la Gran Piedra a los estudios y conteos de aves rapaces migratorias desarrollados en el este de Cuba. Estas pequeñas comunidades se encuentran aledañas a uno de los dos puntos de conteo de rapaces migratorias de la Región. En las entrevistas realizadas a los habitantes, se pudo constatar que algunos pobladores poseían conocimientos básicos sobre las aves rapaces, no así sobre la migración de las mismas. El 100 % de los entrevistados coincidieron en que la principal problemática local se encuentra en la pérdida de aves de corral debido al ataque de rapaces, específicamente el endémico cubano amenazado Accipitter gundlachi (Gavilán colilargo). Los talleres lograron crear espacios de intercambio y reflexión acerca de la importancia de la conservación de las rapaces en la región. Los comunitarios regresaron a sus prácticas diarias, pero esta vez pensando en el modo de contribuir a la conservación de las aves rapaces a partir de los nuevos conocimientos. Esta vinculación de cooperación y sensibilización, permitió un acercamiento de los pobladores con los investigadores y voluntarios que trabajan en el conteo de aves rapaces en Cuba y la retroalimentación del saber científico con el saber popular