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What triggers facultative winter migration of Great Bustard ( Otis tarda ) in Central Europe?
Abstract
The Great Bustard is on the brink of extinction in Central Europe. Its population is known to suffer high mortality during
hard winters, particularly when severe weather conditions cause migration. Long-term winter food management in two populations
in Germany did not prevent migration events. To identify migration-triggering factors we tested the potential influence of
snow, temperature, phase of winter and development of a tradition of migration. Comparing migratory behaviour with long-term
local weather records, we found that snow cover is a much stronger trigger for migration than frost and low temperatures.
We conclude that snow heavily affects the Great Bustard’s energy balance mediated not only by limited food access but also
by the particular properties of its plumage. This could explain migration events despite food availability and is consistent
with our results concerning a tendency for females to undertake facultative winter migration more than males. Available data
are currently insufficient to confirm or reject the idea that Great Bustard populations develop a tradition of migratory behaviour
following a previous winter migration, and we found no evidence for a decrease in the disposition of the Great Bustard to
migrate during the course of winter.
... Previous research on this species in Europe has found that inclement winter weather affects breeding phenology (Biczó and Péczely, 2007), and normally sedentary populations of the Great Bustard in Europe (O. t. tarda) are observed to undertake facultative migration under conditions of snow cover (Block, 1996;Streich et al., 2006). ...
... The Great Bustard also lacks a uropygial gland, which produces oils used to waterproof feathers (Jacob and Ziswiler, 1982). Great Bustards roosting on snow encounter cooling effects of the snow itself, as well as the thermal challenge of plumage dampened by any snow melted by body heat (Streich et al., 2006). We expect that these dietary and thermal challenges initiate a stress response during snowfall or periods of snow cover, activating the HPA axis and the release of CORT from the adrenal gland (Cockrem, 2007). ...
... During severe winter weather, supplementary food is provided and snow cover is cleared to provide access to forage in Central Europe (Bankovics and Széll, 2014;Lóránt and Bankovics, 2013;Streich et al., 2006). This both decreases the chance that these birds will undertake facultative migration, which is associated with high mortality, and improves energy intake. ...
... The most recent catalogue of the birds of the Balearic Islands is the collective work published by the GOB (2011), in which the Great Bustard is not present despite this publication's collation of all the records of wild bird species since 1801. From a much earlier period, Florit et al. (1989) report Streich et al. 2006). The dotted lines represent the accidental observations registered at extreme distances from breeding populations; the dots correspond to records in the winter of 1830 for Italy (Moltoni 1968) and Menorca. ...
... Figure 1 shows a map of Europe with the mean January temperatures for that year taken from a model by Casty et al. (2007). Also indicated are the winter migratory patterns of Great Bustards from eastern Germany and Hungary (Streich et al. 2006), as well as the locations of the specimens found on Menorca (Sanxo ca. 1845) and observations made in Italy in the winter of 1830 (Moltoni 1968). ...
... Two of the factors that determine the tendency to undertake dispersive movements in winter are sex and age since females and immature individuals are more likely to migrate than adult males (Ludwig 1983). In their study of factors that trigger facultative winter movements in Great Bustards, Streich et al. (2006) concluded that heavy snow affects this species' energetic balance, in part by limiting access to food, but also due to the fact that bustards' plumage lack an uropygial gland and so these birds are unable to adequately waterproof their feathers. According to these authors, this factor together with the smaller size of females would explain their tendency to undertake more facultative migrations in winter. ...
This note reviews the historical information available concerning the irregular occurrence during winter of the Great Bustard Otis tarda in the Balearic Islands. It also documents the presence of the species on the island of Menorca in the 19th century (an adult female or an immature male in December 1807 and another on January 1830) based on an unpublished manuscript by Josep Sanxo. The analysis of observations within the biogeographical context of winter irruptions by central European Great Bustards suggests that this region is the probable origin of these vagrant birds in the Balearic Islands.
... The most recent catalogue of the birds of the Balearic Islands is the collective work published by the GOB (2011), in which the Great Bustard is not present despite this publication's collation of all the records of wild bird species since 1801. From a much earlier period, Florit et al. (1989) report Streich et al. 2006). The dotted lines represent the accidental observations registered at extreme distances from breeding populations; the dots correspond to records in the winter of 1830 for Italy (Moltoni 1968) and Menorca. ...
... Figure 1 shows a map of Europe with the mean January temperatures for that year taken from a model by Casty et al. (2007). Also indicated are the winter migratory patterns of Great Bustards from eastern Germany and Hungary (Streich et al. 2006), as well as the locations of the specimens found on Menorca (Sanxo ca. 1845) and observations made in Italy in the winter of 1830 (Moltoni 1968). ...
... Two of the factors that determine the tendency to undertake dispersive movements in winter are sex and age since females and immature individuals are more likely to migrate than adult males (Ludwig 1983). In their study of factors that trigger facultative winter movements in Great Bustards, Streich et al. (2006) concluded that heavy snow affects this species' energetic balance, in part by limiting access to food, but also due to the fact that bustards' plumage lack an uropygial gland and so these birds are unable to adequately waterproof their feathers. According to these authors, this factor together with the smaller size of females would explain their tendency to undertake more facultative migrations in winter. ...
This note reviews the historical information available concerning the irregular occurrence
during winter of the Great Bustard Otis tarda in the Balearic Islands. It also documents the
presence of the species on the island of Menorca in the 19th century (an adult female or an immature male in December 1807 and another on January 1830) based on an unpublished manuscript by Josep Sanxo. The analysis of observations within the biogeographical context of winter irruptions by central European Great Bustards suggests that this region is the probable origin of these vagrant birds in the Balearic Islands.
... Great bustards in central Europe tend to be sedentary, though short migrations by some populations, or some individuals in a population, have been observed (Bankovics and Sz é ll 2006). Irregular irruptive movements of up to 650 km have been recorded for these populations in response to severe winter weather (Farag ó 1990, Block 1996, Streich et al. 2006. ...
... Given that these eastern breeding populations are subject to similar climatic and wind patterns, we hypothesize that the migratory routes of great bustards in eastern Mongolia parallel the southeasterly routes we have identifi ed for central Mongolian bustards. If this hypothesis Given these observations and the tendency of otherwise sedentary central European great bustards to migrate in adverse weather conditions (Streich et al. 2006), it is likely that harsh continental winters drive the observed long-distance migration of Asian great bustards breeding on the Mongolian Plateau. Indeed, northerly and northwesterly winds arising from the Siberian high-pressure system responsible for low winter temperatures in the region (Lydolph 1977, Gong andHo 2002) may facilitate the south easterly migration of great bustards. ...
... In contrast to the severe winter temperatures described above for Kh ö vsg ö l Aimag, mean January temperatures in Xi ' an, China, remain around 0 ° C (Watts 1969, World Meteorolo gical Organization 1996. Th rough migration, great bustards may avoid not only cold temperatures, but also conditions of food shortage due to snow cover (Streich et al . 2006). Th e range of migratory rates we observed for Asian great bustards overlapped with rates observed and expected for other large-bodied birds, such as swans, Cygnus spp., and geese, Anser spp. (Pennycuick 1989, Hedenstr ö m andAlerstam 1998). Th e houbara bustard Chlamydotis undulata , a sister species (Broders et al. 2003) which also br ...
The range of the great bustard stretches 10 000 km across Eurasia, one of the largest ranges of any threatened species. While movement patterns of the western subspecies of great bustard are relatively well-understood, this is the first research to monitor the movements of the more endangered Asian subspecies of great bustard through telemetry and to link a breeding population of Asian great bustards to their wintering grounds. Using Argos/GPS platform transmitter terminals, we identified the annual movement patterns of three female great bustards captured at their breeding sites in northern Mongolia. The 4000 km round-trip migration we have recorded terminated at wintering grounds in Shaanxi, China. This route is twice as long as has previously been reported for great bustards, which are among the heaviest flying birds. The journey was accomplished in approximately two months each way, at ground velocities of 48–98 km h−1, and incorporated multiple and variable stopover sites. On their wintering grounds these birds moved itinerantly across relatively large home ranges. Our findings confirm that migratory behavior in this species varies longitudinally. This variation may be attributable to longitudinal gradients in seasonality and severity of winter across Eurasia. The distance and duration of the migratory route taken by great bustards breeding in Mongolia, the crossing of an international border, the incorporation of many stopovers, and the use of a large wintering territory present challenges to the conservation of the Asian subspecies of great bustard in this rapidly changing part of the world.
... Both sexes showed a partial migration pattern, in agreement with the findings from previous studies in other populations in Spain (Alonso et al. 2000; Morales et al. 2000; Palacín 2007), which suggests that partial migration may be the norm in this species, as it is also in most bird species (Lundberg 1988; Cristol et al. 1999; Berthold 2001). In contrast to central Europe, Russia and Mongolia, where females tend to migrate in higher proportion than males (Streich et al. 2006 ; H. Watzke , cited in Streich et al. 2006), we found that the proportion of migratory males was much higher than that of migratory females. However, excluding males migrating northwards to summering areas and selecting only those males that used an autumn– wintering area (30 males that used a second postbreeding area plus the four southernmost black dots inFig. ...
... Both sexes showed a partial migration pattern, in agreement with the findings from previous studies in other populations in Spain (Alonso et al. 2000; Morales et al. 2000; Palacín 2007), which suggests that partial migration may be the norm in this species, as it is also in most bird species (Lundberg 1988; Cristol et al. 1999; Berthold 2001). In contrast to central Europe, Russia and Mongolia, where females tend to migrate in higher proportion than males (Streich et al. 2006 ; H. Watzke , cited in Streich et al. 2006), we found that the proportion of migratory males was much higher than that of migratory females. However, excluding males migrating northwards to summering areas and selecting only those males that used an autumn– wintering area (30 males that used a second postbreeding area plus the four southernmost black dots inFig. ...
... The proportions of migrants vary not only at a large geographical scale through the Palaearctic distribution range of the species, but also between regions in Spain (Alonso et al. 2000; Morales et al. 2000; Palacín 2007 ), probably because each population is adapted to local ecological conditions. Eastern European and Asian Great bustards are obligate migrants in winter (Glutz et al. 1973; Watzke et al. 2001; Watzke 2007 ), and some populations in central Europe are facultative migrants in response to extreme weather conditions (Dornbusch 1981; Block 1996; Streich et al. 2006). The second sexual difference, namely the earlier departure dates in males, can be explained by the differential investment of both sexes in reproduction and is thus consistent with the specialization hypothesis of sexual segregation. ...
We explored migration patterns in Great bustards (Otis tarda), a species that shows strong sexual selection and the most extreme sexual size dimorphism among birds. The aim was to explain differential migration, examining whether Great bustards fulfil the main predictions of bird migration theory hypotheses and sexual segregation theory hypotheses. We radio-tracked the seasonal movements of 65 males and 68 females in central Spain. We found four main sexual differences. First, the proportion of migratory males was higher than that of migratory females (86% vs. 51%). Second, males abandoned the leks immediately after the mating season (late May to early Jun.), whereas females remained there for another 3–7 mo. Third, 54% of the migratory males used two different post-breeding areas, the first located northwards at 82 km from the breeding sites in summer, and the second southwards at 50 km in autumn–winter. Migratory females used only one area in autumn–winter which coincided geographically with that of males. And fourth, males returned to the breeding areas earlier (between Sep. and Mar.) than females (between Jan. and Apr.). These results show that the Great bustard is a differential migrant by sex in central Spain and support the weather sensitivity hypothesis (males were less tolerant to summer heat) and the specialization hypothesis (exclusive maternal care of the brood by females). Sexual differences in migratory behaviour are probably ultimately determined by the strong sexual selection in this species.
... We utilised all our data sources along with some publications from other countries in the species' range (e.g. Farago 1990, Streich et al. 2006, Geacu 2016 to estimate the potential movement patterns of the species within and through Turkey. ...
... Records of Great Bustards migrating along the Bosphorus and on the Turkish Black Sea coast are intriguing and need more research. Great Bustard populations in central and eastern Europe and Ukraine can perform facultative movements in winter in response to decreasing temperatures and snowfall, reaching as far as Italy, Romania, and Greece (Farago 1990, Kollar 1996, Streich et al. 2006, Geacu 2016. It is possible that some of these wintering individuals might occasionally migrate to the Thracian part of Turkey and across the Bosphorus into Anatolia. ...
... We utilised all our data sources along with some publications from other countries in the species' range (e.g. Farago 1990, Streich et al. 2006, Geacu 2016 to estimate the potential movement patterns of the species within and through Turkey. ...
... Records of Great Bustards migrating along the Bosphorus and on the Turkish Black Sea coast are intriguing and need more research. Great Bustard populations in central and eastern Europe and Ukraine can perform facultative movements in winter in response to decreasing temperatures and snowfall, reaching as far as Italy, Romania, and Greece (Farago 1990, Kollar 1996, Streich et al. 2006, Geacu 2016. It is possible that some of these wintering individuals might occasionally migrate to the Thracian part of Turkey and across the Bosphorus into Anatolia. ...
The Great Bustard Otis tarda is a globally threatened species with populations inhabiting the steppe zones of Turkey. In recent decades, its populations in Turkey have suffered severe declines in range and size. Although the remaining populations are in urgent need of protection, there has been no national-scale study on the species since 2009, and huge information gaps remain concerning its range, abundance, and movements in the country. Here, we combined data from five years of fieldwork together with all available sight and literature records to present up-to-date estimates of distribution and population size in Turkey, to better understand its movement patterns, to reveal its recent and historical population changes, and to assess its national extinction risk and threats. We find that the species' breeding population has shrunk by 20-29% over the last five years, and there are only 559-780 breeding Great Bustards in Turkey distributed in two discrete subpopulations. Comparison with historical records shows that the species' range has shrunk by at least 60% since the beginning of the 20th century. We suggest possible migratory routes within and through Turkey and that Turkey might have a higher regional importance for the species than previously thought. Illegal hunting, agricultural intensification, shift to irrigated crops, overgrazing, collision with powerlines, and disturbance are the most severe threats to the species in Turkey. Our national Red List assessment yields an Endangered categorisation. Further studies are needed to understand the metapopulation structure and movements of the species and to conserve its remaining populations in Turkey.
... Populations in Central Europe tend towards sedentary behaviour, but facultative migrations of up to 650 km have been recorded in response to severe winter weather, bringing these birds to states in southern Europe (Block 1996, Streich et al. 2006. Within Central Europe, nonmigratory movements regularly result in these birds crossing international borders. ...
... On migratory and wintering areas in China, Great Bustards suffer from the indiscriminate poisoning of wild birds for supply of meat to "wild foods" restaurants (Shi 2008;Chan & Goroshko 1998, Kessler in litt.). Great Bustards breeding in southeastern Russia, Mongolia, and northern China use this migratory pathway. ...
Proposal to list the global population of Great Bustard on Appendix I, submitted by the Government of Mongolia to the Convention on Migratory Species in 2014
... The migratory status of the eastern European population of the species has been recently confirmed through satellite tracking of six females between their nesting areas east of Saratov, Russia to their wintering areas in southern Ukraine (Watzke et al. 2001;Watzke 2007). Some populations in central Europe are facultative migrants in response to extreme weather conditions during winter (Block 1996;Dornbusch 1981;Farago 1990;Streich et al. 2006). As for the western population, year-round surveys at various populations in Spain reported monthly changes in numbers, which suggested that some seasonal movements did occur (Alonso and Alonso 1990;Hidalgo and Carranza 1990;Hellmich 1991;Alonso et al. 1995). ...
... Such an obligate partial migration system with variable proportions of migrants and sedentary birds has been recently proposed to be possibly universal in birds, allowing selection to act at any time towards complete migratory or complete sedentary behaviour and enabling species to adapt to changing conditions (see Berthold 1999;reviewed in Newton 2008). Directional post-breeding movements to specific summering areas have not been described for northern European or Asian populations of great bustards (Dornbusch 1981;Farago 1990;Block 1996;Morales and Martín 2002;Streich et al. 2006), probably because at these latitudes, the summer temperature is not high enough, resembling the situation in northern Spain. This supports our interpretation that summer migration is a relatively recent adaptation of male great bustards to the very hot climate of southern latitudes in Iberia and probably Morocco, which represent the southern limit of the species' distribution range and the front edge of its expansion from central Europe (Pitra et al. 2000;Alonso et al. 2009). ...
Radio tracking of 142 males captured at 44 leks in Spain showed that partial migration of great bustard males in summer is
a widespread behaviour in many Iberian populations, in contrast to their previously assumed sedentariness. A variable number
of males migrated immediately after mating to summering areas with lower temperatures and human population densities and more
trees and rainfall levels than the breeding sites. Birds selected there fields with trees and sunflower crops which provided
shade during the hottest midday hours and protective cover against predators. Males breeding in areas with higher July temperatures
had a higher tendency to migrate, and males from hotter, southern regions migrated longer distances than those from milder,
northern regions and showed a preferred northward direction. These results confirmed various predictions from the weather
sensitivity hypothesis, suggesting that summer migration of great bustard males represents primarily an adaptation to escape
the summer heat of most breeding areas in central and southern Iberia. The hypothesis that males migrated to benefit from
higher food availability at the summering areas could not be rejected by our results. Finally, migrating males also gained
more tranquillity during the post-breeding moult due to the lower human population density at the summering areas. Summer
migration of Iberian great bustard males may thus be interpreted as a form of behavioural thermoregulation which has not been
described for other Palaearctic populations of this species or for other bird species breeding in temperate latitudes.
... In addition, we found females spent more days in spring than autumn during migration, which may be caused by the long stopover duration in spring (Kessler et al. 2013). Temperature and wind support mainly trigger the migration movement of the Great Bustard (Kessler 2015;Streich et al. 2005). In northern China and Mongolia, weather condition remains harsh and unstable in March. ...
The Great Bustard (Otis tarda) holds the distinction of the heaviest bird to undertake migration as well as the greatest degree of sexual size dimorphism among living birds. Though the migration of the species has been widely discussed in the literature, researchers know little about the migration patterns of the subspecies in Asia (Otis tarda dybowskii), especially the males. In 2018 and 2019, we captured six O. t. dybowskii (five males and one female) at their breeding sites in eastern Mongolia and tagged them with GPS-GSM satellite transmitters. This constitutes the first time that the Great Bustards of the eastern subspecies have been tracked in eastern Mongolia. We found sex differences in migration patterns: males started migration later but arrived earlier than the female in the spring; males had 1/3 of the migration duration and migrated about 1/2 the distance of the female. Additionally, Great Bustards exhibited high fidelity to their breeding, post-breeding, and wintering sites. For conservation, only 22.51% of GPS location fixes of bustards were within protected areas, and less than 5.0% for wintering sites and during migration. Within two years, half of the Great Bustards we tracked died at their wintering sites or during migration. We recommend establishing more protected areas at wintering sites and rerouting or undergrounding powerlines in areas where Great Bustards are densely distributed to eliminate collisions.
... On the other hand, longer migrations are undertaken by the smaller sex in some bird species (e.g. Ketterson and Nolan 1976), and this is documented in the Asian Houbara and both subspecies of Great Bustard (Streich et al. 2006, Combreau et al. 2011. The interannual variation in these movements may increase the risk of collision by taking birds into unfamiliar landscapes (Bernardino et al. 2018). ...
Bustards comprise a highly threatened family of birds and, being relatively fast, heavy fliers with very limited frontal visual fields, are particularly susceptible to mortality at powerlines. These infrastructures can also displace them from immediately adjacent habitat and act as barriers, fragmenting their ranges. With geographically ever wider energy transmission and distribution grids, the powerline threat to bustards is constantly growing. Reviewing the published and unpublished literature up to January 2021, we found 2,774 records of bustard collision with powerlines, involving 14 species. Some studies associate powerline collisions with population declines. To avoid mortalities, the most effective solution is to bury the lines; otherwise they should be either routed away from bustard-frequented areas, or made redundant by local energy generation. When possible, new lines should run parallel to existing structures and wires should preferably be as low and thick as possible, with minimal conductor obstruction of vertical airspace, although it should be noted that these measures require additional testing. A review of studies finds limited evidence that 'bird flight diverters' (BFDs; devices fitted to wires to induce evasive action) achieve significant reductions in mortality for some bustard species. Nevertheless , dynamic BFDs are preferable to static ones as they are thought to perform more effectively. Rigorous evaluation of powerline mortalities, and effectiveness of mitigation measures, need systematic carcass surveys and bias corrections. Whenever feasible, assessments of displacement and barrier effects should be undertaken. Following best practice guidelines proposed with this review paper to monitor impacts and mitigation could help build a reliable body of evidence on best ways to prevent bustard mortality at powerlines. Research should focus on validating mitigation measures and quantifying, particularly for threatened bustards, the population effects of powerline grids at the national scale, to account for cumulative impacts on bustards and establish an equitable basis for compensation measures.
... Besides, we found females spent more days in spring than autumn during migration, which may be caused by the long stopover duration in spring [27]. Temperature and wind support mainly trigger the migration movement of the great bustard [50,51]. In northern China and Mongolia, weather condition remains harsh and unstable in March. ...
Background
The great bustard (Otis tarda) holds the distinction of the heaviest bird to undergo migration as well as the greatest degree of sexual size dimorphism among living birds. Though the migration of the species has been widely discussed in the literature, researchers know little about the migration patterns of the subspecies in Asia (Otis tarda dybowskii), especially the males.
Methods
In 2018 and 2019, we captured six O. t. dybowskii (five males and one female) at their breeding sites in eastern Mongolia and tagged them with GPS-GSM satellite transmitters. This constitutes the first time that male great bustards of the eastern subspecies have been tracked. We combined the tracking data of our only female with other three females from central Mongolia, which was published in previous study for analysis.
Results
We found notable differences between the sexes: 1) males started migration later but arrived early than females in the spring, but not in autumn; 2) males had 1/3 of the migration duration of females (16.44 ± 14.68 days vs. 49.34 ± 21.28 days); 3) males migrated about 1/2 the distance of females (945.13 ± 79.00 km vs. 1922.88 ± 87.08 km). Additionally, we found bustards exhibited high fidelity to their breeding, post-breeding and wintering sites. Indeed, most of the wintering sites found by GPS tracking in this study were also utilized 70 years earlier, according to previous work. For conservation, we found only 22.20% of GPS location fixes of bustards were within protected areas and less than 5.0% for wintering sites and during migration.
Conclusions
Our findings suggest that the migration patterns of eastern great bustards are sex-specific and more conservation effort is needed for the Asian populations of this threatened species.
... Different patterns of resource variation promote different forms of migration and even irregular movements to explore resources that not follow seasonal fluctuations can be considered a migration type or an erratic migration (Van Moorter et al. 2013;Pedler et al. 2014). Individual migration behavior is associated as consequence of demographic aspects (Reid et al. 2018) and when a key environmental resource transcends a critical threshold (Streich et al. 2006). Water depth and flood-pulse are the most important features to quality and quantity of habitats for waterbirds (Tavares et al. 2015). ...
... The area fidelity to the breeding sites in female Great Bustards is very high (Alonso et al. 2000) and the natal dispersion is low (Martín et al. 2008). The Central European Great Bustard populations are considered as facultative migratory, indicating that their migration is triggered by harsh weather (Faragó 1990, Streich et al. 2006, however, a kind of seasonal movement is characteristic even for sedentary females (Alonso et al. 2000). Female Great Bustards can be observed in the study area from spring to autumn and they are not present in winter (own unpublished data), i.e. the place is of primary importance for reproduction. ...
As the whole Palearctic steppe system, its iconic bird, the Great Bustard has also suffered from the ex-pansion of intensive agriculture. The species now typically has stable or growing populations only in protected areas, but negative processes are still prevalent even there. In this study, we present a recent change in a part of the natuRa 2000 site designated for the isolated West Pannonian population. In recent years, a total of 2.3 km Center-pivot and laterally moving linear irrigation systems have been built and 4.7 km of underground pipelines have been laid, with which more than 52% of the 1245,5 ha study area was irrigated by 2020. In comparison to 2009, when the study period has started, the sown area of autumn cereals, one of the main breeding habitats, was roughly halved and the proportion of crops unsuitable for breeding was increased. New crops requiring irriga-tion have emerged with a rate of 30.6% in the last year. Despite the available support, the area of alfalfa, which is the most significant breeding habitat, and is grown almost exclusively in the agri-environmental scheme, has decreased. As a result of habitat degradation, the number of Great Bustard females observed in the area in spring decreased to a small fraction of the beginning. Irrigation farming is expected to increase, as a response to the cli-mate change, but in order to save agro-steppe habitats and their species, the adverse effects of agricultural inten-sification need to be urgently addressed at both local and European levels.
Available: http://ornis.hu/articles/OrnisHungarica_vol28(2)_p74-84.pdf
... For example, ephemeral resource outbreaks with no periodicity often lead to erratic migration (Kingsford et al. 2010, Pedler et al. 2014. Some bird populations exhibit facultative migration when a key environmental factor that drives the availability of resources exceeds a critical threshold (Streich et al. 2006). Partial migration, when a population includes both migratory and resident individuals, often emerges when variability in the distribution of resources is paired with ecological trade-offs-such as density dependence, the energetic cost of migration, or predator avoidance (Chapman et al. 2011). ...
The function of migration is to allow exploitation of resources whose availability is heterogeneous in space and time. Much effort has been historically directed to studying migration as a response to seasonal, predictable fluctuations in resource availability in temperate species. A deeper understanding of how different migration patterns emerge in response to different patterns of resource variation requires describing migration patterns of species inhabiting less predictable environments, especially in tropical and subtropical areas. We provide the first individual‐based, quantitative description of migratory patterns in a subtropical wading bird in the southeastern United States, the wood stork (Mycteria americana). Using GPS tracking data for 64 individuals tracked between 2004 and 2017, we classified migratory behavior at the individual‐year level using information theory‐based model selection on nonlinear models of net squared displacement. We found that the wood stork population is partially migratory, with 59% of individuals seasonally commuting between winter ranges in Florida and summer ranges elsewhere in the population range (migrants), and 28% remaining in a single area in Florida year‐round (residents). Additionally, 13% of storks act as facultative migrants, migrating in some years but not in others. Comparing the distribution of residents and migrants suggests that different migratory strategies might be associated with the use of different or differently distributed resources, possibly including food supplementation from human activities. The existence of facultative migrants shows the potential for plastic change in migratory patterns. Partial migration in wood storks may be an adaptation to high heterogeneity and unpredictability of food resources. We suggest that future research should focus on wading birds as model species for the study of partial migration as an adaptation to heterogeneous and unpredictable environments.
... For example, ephemeral resource outbreaks with no periodicity often lead to erratic migration (Kingsford et al. 2010). Some bird populations exhibit facultative migration when a key environmental factor that drives the availability of resources exceeds a critical threshold (Streich et al. 2006). Partial migration, when a population includes both migratory and resident individuals, often emerges when variability in the distribution of resources is paired with ecological trade-offs -such as density-dependence, the energetic cost of migration, or predator avoidance (Chapman et al. 2011). ...
The function of migration is to allow exploitation of resources whose availability is heterogeneous in space and time. Much effort has been historically directed to studying migration as a response to seasonal, predictable fluctuations in resource availability in temperate species. A deeper understanding of how different migration patterns emerge in response to different patterns of resource variation requires focusing on species inhabiting less predictable environments, especially in tropical and subtropical areas. We provide the first individual-based, quantitative description of migratory patterns in a subtropical wading bird in the Southeastern U.S., the wood stork ( Mycteria americana ). Using GPS tracking data for 64 individuals tracked between 2004 and 2017, we classified migratory behavior at the individual-year level using information theory-based model selection on non-linear models of net squared displacement. We found that the wood stork population is partially migratory, with 59% of individuals seasonally commuting between winter ranges in Florida and summer ranges elsewhere in the population range (migrants), and 28% remaining in a single area in Florida year-round (residents). Additionally, 13% of storks act as facultative migrants, migrating in some years but not in others. Comparing the distribution of residents and migrants suggests that different migratory strategies might be associated with the use of different or differently distributed resources, possibly including food supplementation from human activities. The existence of facultative migrants shows the potential for plastic change of migratory patterns. Partial migration in wood storks may be an adaptation to high heterogeneity and unpredictability of food resources. We suggest that future research should focus on wading birds as model species for the study of partial migration as an adaptation to heterogeneous and unpredictable environments, by comparing populations of the same species across different wetland systems and sympatric populations of species that differ in their resource acquisition mechanisms.
... The Great Bustard is a globally threatened species that survives in highly fragmented populations, mainly in dry cereal farmland across the Palaearctic, from the Iberian Peninsula to eastern China (Palacín & Alonso 2008;IUCN 2015). The migratory patterns of this species vary: partial and sexually differential in southern Europe (Palacín et al. 2009), facultative in central Europe (Streich et al. 2006), and obligate in the northernmost populations in Russia and Mongolia (Watzke 2007;Kessler et al. 2013). In Spain, Great Bustards are partial migrants; sedentary and migratory birds coexist in the same breeding groups. ...
Many bird populations have recently changed their migratory behaviour in response to alterations of the environment. We used 16-year data of the partial migratory great bustard (Otis tarda) males, including population counts and 180 lifelong radio-tracked individuals, to test for differences in survival rates between migratory and sedentary individuals and evaluate possible effects of these differences on the migratory pattern of the population. Overall, great bustards followed a partial migration pattern, with 65% migrant and 35% sedentary males. The average distance between breeding and post-breeding areas of migrant individuals was 89.9 km, whereas the longest movements performed by sedentary males averaged 3.8 km. Breeding group or migration distance had no effects on survival. However, migrants experienced 2.4 to 3.5 times higher mortality than sedentary birds. Collision with power lines was the main cause of non-natural death of marked males (37.6% of all deaths), and migratory birds died by collision more frequently than sedentary birds (21.3% vs. 6.3%). Throughout the study period, we observed a significant increase in the sedentary tendency of the monitored population. The proportion of sedentary individuals changed from 17% in 1997 to 45% in 2012. These results were supported by marked males: the proportion of migratory individuals decreased from 86% in 1997-1999 to 44% in 2006-2010. The observed decrease in the migratory tendency was not related to climatic changes or variations in habitat quality. Our findings suggest that human-induced mortality during migration may be an important factor shaping the migration patterns of species inhabiting humanized landscapes. This article is protected by copyright. All rights reserved.
... Some of these most favourable areas in the future are in accordance with those found more suitable for the species by Synes and Osborne [34]. Additionally, we obtained unfavourable areas for the great bustard in central Europe where there has been a dramatic decline of the species' populations [71]. Thus, the situation may be even worse if climate change predictions are met. ...
We modelled the distribution of two vulnerable steppe birds, Otis tarda and Tetrax tetrax, in the Western Palearctic and projected their suitability up to the year 2080. We performed two types of models for each species: one that included environmental and geographic variables (space-included model) and a second one that only included environmental variables (space-excluded model). Our assumption was that ignoring geographic variables in the modelling procedure may result in inaccurate forecasting of species distributions. On the other hand, the inclusion of geographic variables may generate an artificial constraint on future projections. Our results show that space-included models performed better than space-excluded models. While distribution of suitable areas for T. tetrax in the future was approximately the same as at present in the space-included model, the space-excluded model predicted a pronounced geographic change of suitable areas for this species. In the case of O. tarda, the space-included model showed that many areas of current presence shifted to low or medium suitability in the future, whereas a northward expansion of intermediate suitable areas was predicted by the space-excluded one. According to the best models, current distribution of these species can restrict future distribution, probably due to dispersal constraints and site fidelity. Species ranges would be expected to shift gradually over the studied time period and, therefore, we consider it unlikely that most of the current distribution of these species in southern Europe will disappear in less than one hundred years. Therefore, populations currently occupying suitable areas should be a priority for conservation policies. Our results also show that climate-only models may have low explanatory power, and could benefit from adjustments using information on other environmental variables and biological traits; if the latter are not available, including the geographic predictor may improve the reliability of predicted results.
... vernal a gran escala.La altitud tiene una gran influencia sobre la innivación y la mayor impredecibilidadseveridad climática, que indirectamente afectan a la disponibilidad de alimento. La innivación aumenta con la altitud y la nieve perdura más en zonas altas y más frías, de manera que se reduce la accesibilidad de los recursos tróficos del suelo.Streich et al. (2006) confirmaron que, precisamente, la restricción temporal al alimento causada por las nevadas era el factor desencadenante de migraciones invernales facultativas en poblaciones de avutarda de Europa central. Por otro lado, la mayor frecuencia y severidad de los temporales de viento y frio de las zonas más elevadas también comprometen las e ...
... Food shortage due to a deep, persistent snow cover can cause losses because of starvation (Eschholz, 1996). Furthermore it can force Great Bustards to leave their wintering areas (Bankovics, 2005;Faragó, 2005;Streich et al., 2006). These facultative migration movements can also result in heavy losses because of moving through unfamiliar sites (Eschholz, 1996;Faragó, 2005). ...
Great Bustards face many threats, both natural (such as predation and harsh weather conditions) and anthropogenic (collisions with overhead power lines, intensive agriculture, disturbance , habitat fragmentation and-deterioration). Depending on how these issues are addressed in the countries involved, Great Bustard populations may suffer or prosper in the future. Within the Austrian LIFE and LIFE+ projects a number of conservation measures were introduced to reduce especially anthropogenic threats to Great Bustards. As a result, the Great Bustard populations in Austria and the West Pannonion region have been increasing in recent years.
... Furthermore, access to these winter grazing areas should be ensured during the whole winter. Removal of snow, which may become deep and crusty, is an important action to undertake (Nagy 2009 ), since a snow cover of only 5 cm covers all potential food plants of Great Bustards, which they then have to pull out of the snow using only their bills (Streich et al. 2006 ). ...
Winter oilseed rape represents an important food source for Great Bustards. Great Bustard surveys during four consecutive winters (2005/2006–2008/2009) were used to identify characteristics of oilseed rape fields, which increase their attractiveness for the species in its West Pannonian wintering area. The study was conducted in study areas in Eastern Austria, around the Austrian– Slovakian–Hungarian border and in the Hungarian Moson Plain. To test for effects of field size and isolation of fields from other rape fields, and the distance to the nearest paved road on occurrence and abundance of Great Bustards (maximum number of birds counted in individual rape fields per winter), we calculated generalized linear mixed models (GLMMs) including all three predictor variables as fixed effects and winter as random effect for each of the three study areas. Field size most strongly affected occurrence and abundance of Great Bustards. The availability of large (>>15 ha) winter rape fields far from paved roads is recommended as a prime conservation measure to improve the quality of rape fields as foraging habitat for Great Bustards during the winter months (November–March).
... Also, when looking at recovery data of the nearest population in Hungary, in spite a total of 545 birds had been ringed in Hungary between 1951 and 2006, only one foreign recovery (in Albania) has been known until now (Faragó, 2009). However, according to the movements of the central European birds (Streich et al., 2006) it is reasonable to conclude that Great Bustards being observed in Croatia belong to the Central European population and originate from Hungarian, Austrian and probably Serbian (at least the observations in eastern Croatia) breeding populations. From these three populations, the Hungarian is the most numerous, but it faced a strong decline during the 20th century. ...
In the 20th century the Great Bustard (Otis tarda) was a passage migrant and winter visitor in Croatia. Birds observed in Croatia belong to the Central European population for which the harsh winters were identified as the most important cause for adult bird mortality. We investigate the mortality factors of adult birds in Croatia. Data on the occurrence of the Great Bustard in Croatia were collected from the literature and from feedback of a questionnaire distributed among hunters in 2004. During the 20th century, 35 records of at least 60 birds were reported. Occurrences were more frequent at the beginning of the century, but they turned scarcer and more irregular in later years. Birds were observed between October and April. During winter, Great Bustards were more frequently recorded in Southern Croatia, while records from Northern Croatia dominated during autumn and spring. From the total number of records, 57% referred to birds being shot. Shooting occurred be-tween December and March mostly in Southern Croatia. The Great Bustard is strictly protected by law in Croatia since 1967, with one recorded case of birds being illegally shot since the hunting ban has been imposed.
... Several potential factors have been identified for spring arrival of songbirds on their breeding grounds in Europe [19], such as local weather, large scale weather patterns and vegetation greenness. Adverse weather conditions, snow cover and depletion of food resources can induce migration in facultative migrants [20][21][22] Similarly, general winter harshness has been shown to influence the tendency of ducks to migrate in winter [23][24][25], a behavior that might be induced by the freezing of lakes. ...
The ontogeny of continent-wide navigation mechanisms of the individual organism, despite being crucial for the understanding of animal movement and migration, is still poorly understood. Several previous studies, mainly conducted on passerines, indicate that inexperienced, juvenile birds may not generally correct for displacement during fall migration. Waterbirds such as the mallard (Anas platyrhynchos, Linnaeus 1758) are more flexible in their migration behavior than most migratory songbirds, but previous experiments with waterbirds have not yet allowed clear conclusions about their navigation abilities. Here we tested whether immature mallard ducks correct for latitudinal displacement during fall migration within Europe. During two consecutive fall migration periods, we caught immature females on a stopover site in southeast Sweden, and translocated a group of them ca. 1,000 km to southern Germany. We followed the movements of the ducks via satellite GPS-tracking and observed their migration decisions during the fall and consecutive spring migration. The control animals released in Ottenby behaved as expected from banding recoveries: they continued migration during the winter and in spring returned to the population's breeding grounds in the Baltics and Northwest Russia. Contrary to the control animals, the translocated mallards did not continue migration and stayed at Lake Constance. In spring, three types of movement tactics could be observed: 61.5% of the ducks (16 of 26) stayed around Lake Constance, 27% (7 of 26) migrated in a northerly direction towards Sweden and 11.5% of the individuals (3 of 26) headed east for ca. 1,000 km and then north. We suggest that young female mallards flexibly adjust their migration tactics and develop a navigational map that allows them to return to their natal breeding area.
... Deep snow cover was found to be a much stronger trigger of facultative migration than low environmental temperature. Available food apparently does not affect this migration and thus other factors besides covered food supply may also be important (Streich et al., 2006). ...
This chapter summarizes behavioral and hormonal responses to weather events, mostly in birds, and how coping mechanisms provide flexibility to deal with an increasingly capricious environment in which global climate change and human disturbance provide further challenges. Typically, vertebrates show changes in morphology, physiology, and behavior in anticipation of the predictable changes so that they can respond appropriately to the changing seasons. An example of this would be the development of the reproductive system before the breeding season so that individuals are able to begin breeding as soon as environmental conditions are favorable. By contrast, organisms must respond to unpredictable changes in the environment, only during or after the perturbation, as there is no way of predicting the actual onset. The chapter focuses on the hypothalamo-pituitary-adrenal cortex axis and its actions on the responses to weather acting as direct life history stages. This response is common to most vertebrates and there are remarkably comparable parallel responses of very different organisms, such as fish and mammals, to those perturbations. Climate is defined by average weather conditions over many years. Organisms may time life-history stages, such as breeding, to occur at optimal times for reproductive success. Only when weather events go beyond the climatic norm for a particular time of year are allostatic overload and stress likely. It is at this time that increases in corticosterone would be important resulting in activation of the emergency life-history stage and coping.
... Predictor P b se Lower CI Upper CI Area of vineyards 1.00 0.007 0.003 0.0002 0.0133 Area diversity (SDI) 1.00 )5.460 2.16 )9.7 )1.23 Area of irrigated farmland 1.00 )0.027 0.014 )0.054 0.0005 Road length 0.57 )0.0002 0.0001 )0.001 0.00005 Area of open-wooded oak-tree 0.56 )0.005 0.006 )0.016 0.006 Terrain undulation 0.25 )0.166 0.157 )0.474 0.141 Minimum distance to nearest road 0.24 0.001 0.001 )0.001 0.002 winter ( Watzke 2007, Kessler 2010), to facultative and weather-dependent in German or Hungarian populations ( Streich et al. 2006). Breeding areas of migrant females concur with breeding and wintering areas of sedentary females. ...
A detailed knowledge of the habitat requirements of steppe birds living in farmland habitats is necessary to identify agricultural practices compatible with their conservation. The globally threatened Great Bustard Otis tarda is a partial migrant in central Iberia, but factors affecting its winter habitat use have not been identified. We assessed habitat differences between breeding and wintering areas and winter habitat selection of radiotagged migrant female Great Bustards in central Spain. Of 68 tagged females, 35% moved to wintering areas located 64.3 ± 24.0 km south of their breeding areas, and 80% wintered in a single area of c. 236 km2. A census of the population in this area identified it as one of the most important wintering areas of this species in the world, holding c. 1500 individuals. There were significant differences between breeding and wintering habitats of individually marked migrant females. Compared with breeding areas, wintering areas of migrant females were located further from roads and urban nuclei, had lower human population densities and area of urban developments, and a higher diversity of land-use types, with less cover of cereals and more vineyards and olive groves. Within this area, radiotracked migrant females preferred sites with more vineyards and a lower land-use diversity. Our results highlight the importance of traditional Mediterranean dry farmland mosaics, and suggest that different conservation strategies are needed for migrant and resident populations in winter to secure the conservation of suitable wintering habitat for Great Bustards in the Iberian Peninsula.
... For example, the migratory tendency and distance found for females in central Spain clearly differs from those of females in NW Spain (Alonso et al. 2000, Palacín et al. 2009). The patterns found in Iberian populations also differ from the behavior described at other areas of the species' distribution range (Streich et al. 2006, Palacín 2007, Watzke 2007, Kessler 2010). We also found changes in migratory behavior of individual birds between consecutive years. ...
Factors responsible for individual variation in partial migration patterns are poorly known, and identifying possible causes of these changes is essential for understanding the flexibility in migratory behavior. Analyzing 190 life histories of great bustards Otis tarda radio-tagged in central Spain, we investigated the changes in migratory tendency across lifetime in this long-lived bird, and how migratory flexibility is related to individual condition. In females migratory behavior was not fixed individually. For every age class there was a fraction of ca 15–30% of females that changed their migratory pattern between consecutive years. Migrant females tended to remain sedentary in years when they had dependent young to attend. These findings show that the female migratory tendency is a behaviorally flexible, condition-dependent trait. Immature females usually acquired their migratory behavior by learning from the mother in their first winter or by social transmission from other migratory females in their second winter. As for immature males, their summer migratory behavior was not related to mother–offspring transmission, but learned from adult males. We found that their age-related increase in migratory tendency was associated to a greater integration in flocks of migrant adult males. These results show that within the partial migration system, cultural transmission mechanisms, either mediated by kin or not, and individual condition, may contribute to shape the migratory tendency. Our study reinforces the view that the migratory behavior is an evolutionary complex trait conditioned by the interaction of individual, social and environmental factors. Particularly in long-lived species with extended parental care, the inherited migration program may be shaped by mother–offspring and social transmission of migratory patterns.
Changes in future climate will alter the geographic distributions of many species. Species distribution models have evolved as a powerful tool for predicting potential species distributions and assessing habitat suitability. The Asian Great Bustard (Otis tarda dybowskii), a long-distance migratory bird, is listed as a globally threatened species and is highly dependent on farmlands during the wintering period. In this study, 78 occurrence points and 15 environmental variables were used to estimate the potential distribution under current conditions and four future climate scenarios by using the maximum entropy model. With current climatic conditions, the highly suitable areas of wintering Asian Great Bustard in China were mainly concentrated on the Northeast Plain, Guanzhong Plain, and North China Plain (33°–48° N, 109°–127° E). Under future climatic scenarios, the geographic distribution of wintering Asian Great Bustard would remain stable, and the total area of suitable habitats would increase to varying degrees until the end of this century. Our results can be used to define highly suitable areas for conservation management plans for this threatened species.
Land-use change is the single most important cause of global biodiversity loss. Over
millennia, European grassland birds concentrated in low-intensity agro-steppe
habitats that are now experiencing intensification largely in line with European
market forces. Great Bustard (Otis tarda, GB) is a globally threatened species and a
symbol of the Iberian agro-steppes. In Extremadura (Spain) and Alentejo (Portugal)
the conservation status of GB and other agro-steppe species is unclear. GB
subpopulations were monitored in these two regions between 1985 and 2015, and
their trends were related to land-use changes using open-access databases. There
was regional variation in trends, and I report here a sharp decline in numbers across
the study area since 2010. Trends were not related to moderate reduction of agro
steppe habitats, but were negatively related to changes in livestock densities,
implying that livestock management of habitats is crucial for conservation. Using
field counts in spring 2017 across a network of EU Special Protected Areas (SPAs)
designated to protect GB, I found that GB is not a good indicator for other agro
steppe species of conservation concern. Selection of further indicator species is
recommended for better conservation of agro-steppe bird assemblage. In an SPA in
Extremadura, GB productivity rates decreased dramatically between 2005 and
2016. If current productivity rates continue, population modelling predicts a steep
decline in numbers at this site. Results of this study raise concerns over the function
of the SPA network in Extremadura and Alentejo to protect GB and their agro
steppe habitat. To sustain numbers of GB and other agro-steppe species, their
habitats need to be better protected from further intensification, including control
of livestock densities, preferably using agro-environmental schemes in PAs.
Great bustard (Otis tarda) is a large bird,inhabiting in the steppe and semi-desert areas of Eurasia. During the last several decades,the distribution area and number of great bus-tard have declined drastically,and this species has disappeared in many parts of its former vast natural habitat due to the land-use changes,negative impact of land privatization, over-hunting and poaching. Great bustard is ranked as a grade I key protected wildlife species in China and defined as Vulnerable (VU) in the IUCN Red List of Threatened Species. Scientists from different countries have conducted numerous researches and published a lot of papers devoted to great bustard’s distribution,population number,diet,habitat selection,reproduction ecology,migration and behavior. In this paper,we review and summarize all available information for this species in order to find and suggest new,more detailed researches and directions for further investigations. © 2015, editorial Board of Chinese Journal of Ecology. All rights reserved.
Capsule The occurrence of oilseed rape increased main prey abundance and breeding success of
Common Buzzards.
Aims We tested whether the occurrence of oilseed rape influences the abundance of Common Voles, i.e.
the main prey of Common Buzzards and so also nesting activity and breeding success of Common
Buzzards.
Methods The study was carried out in 2005–2012 in a 38 km2 area in western Poland, where oilseed rape
plantations (12–106 ha) covered 18% of the agricultural land. The number of active burrow entrances was
used as an index of vole abundance in various crops, and Buzzard breeding performance, i.e. the
occurrence of annual nesting attempts in individual long-term nesting sites as well as the presence and
number of fledglings, was estimated by observations of their nests.
Results The index of vole abundance was highest in oilseed rape, and judging by the proportion of active
burrow entrances (33–77%), the plantations of rape typically supported a larger portion of the local vole
population than other crops. The acreage of oilseed rape fields around individual nesting sites of
Buzzards did not affect the probability of nesting attempts in these sites. However, the probability of
successful nesting and the number of fledglings per successful nest increased with the area of oilseed
rape around the Buzzard nesting sites.
Conclusion The occurrence of oilseed rape may positively affect prey availability and in turn the breeding
success of Buzzards. The spread of oilseed rape may therefore also be beneficial for other vole-eating
raptors hunting in the agricultural landscapes.
Watzke, H., H. Litzbarski, O. S. Oparina & M. L. Oparin 2001: The migration of Great Bustards Otis tarda from the Saratov region (Russia) - first results of a satellite tracking study. Vogelwelt 122: 89 - 94.
In 1999 three female Great Bustards were fitted with satellite transmitters within the German-Russian project „Protection of Great Bustards in the Saratov region". One female was located only in the breeding area for 5 months. At this time it used a home-range of some 40 km2. The other bustards left the breeding grounds in the second decade of October or in the second decade of November, respectively. They wintered in the south of Ukraine in the area between the cities Cherson and Melitopol and the Ukrainian Crimea peninsula. They left the wintering ground in the end of march. Since the beginning of April they were in the breeding area again. The female Great Bustards needed 5 to 8 days for the 1000 km long way (mean speed: 125 - 200 km/day, maximum 275 km/day). They interrupted the migration for 3 to 4 days. Potential threats for great bustards in the wintering grounds are discussed, especially hunting.
Key words: Great Bustard, Otis tarda, migration, satellite-tracking, protection, Russia, Ukraine.
We examined the seasonal movements of wing-tagged and radio-marked adult female Great Bustards Otis tarda in a population in northwestern Spain. Four different movement patterns were found: females that migrated between breeding and wintering areas (20%), females that only left their year-round home range area to mate (32%), females that migrated from a wintering-mating area to a nesting-summering area (16%), and females that stayed all year round within a relatively small home range area (32%). All females displayed fidelity to their nesting and wintering areas, and most also showed fidelity to their leks. Migration patterns were not affected either in timing or distance by breeding success. The maximum distance between natal and dispersal locations during their first year of life was significantly higher in migratory females than in sedentary ones. These patterns explained the seasonal variations in population numbers observed in the study area. Surveys showed that the number of females increased from 600–700 breeding birds, with 1,000–1,100 birds present from October to March.
World status of the Great Bustard (Otis tarda) with special attention to the Iberian peninsula populations.- The aim of this paper is to review the current world status of this endangered and poorly known species. Its distribution and movement are analysed. The extreme variability of movement patterns (from migrant to sedentary, east to west, along the distribution area) classify the species as a partial migrant. A retrospective review shows that Great Bustard populations levels are decreasing, probably due to the increasing isolation of populations. There are only about 22480 - 23860 individuals from east of China to the Iberian peninsula and north-west Africa. The Spanish Great Bustard population may be 43-51% of the world total, Extremadura being the most important nucleus with almost one- fourth of the world population. The spanish population in the last decade is reviewed, showing a decrease in most traditional areas with the exception of Castilla-Leon and Extremadura. On the other hand, seasonal fluctuations in populations sizes denote the possibility of movement among the different populations.
The sections on Field characters, Habitat, Distribution, Population, Movements, Food, Social pattern and behaviour, Breeding, Plumage, Measurements, Weights, and Geographical variation have been updated and partially re-written. Two new sections have been created on Conservation and Survival. New information is given on age and timing of acquisition of full adult plumage, habitat use in Iberia, changes of range and population numbers in most European countries, seasonal movements and migration in Iberia, central Europe, Russia and Turkey, as well as juvenile dispersal, diet composition in Spanish populations, organization of mating system, correlates of display rate and male mating success, timing of breeding, nesting substrate, clutch size in Iberia and Hungary, weather correlates of population productivity, individual correlates of female breeding success, parental care, and chick independence timing. Additionally, new measurements and weights of captured free-living juvenile and adult birds are provided, as well as recent results on phylogeography in Europe, based on mitochondrial DNA. The Survival and Conservation sections respectively, describe juvenile and adult survival rates and longevity in different Spanish regions, and summarize the main threats and management priorities for the species.
In 1981, 2924 Oris tarda were counted, in 1985 2691, and in 1990 merely 1362. The main causes for the losses were destruction of clutches as the result of agrotechnological procedures (84.4% and 79.0% of losses in 1985 and 1988, respectively) and the death of birds during migration, due to severe winters. -from Author
In a discussion of the evolution of gene flow, Wilson (1975, p. 103) pointed out that a tendency for different sexes and age groups to migrate differentially can exert a profound influence on social structure. In this paper, I suggest that the reverse is equally true: a basic social structure—namely, the dominance hierarchy—can strongly influence the differential dispersal and migration of different sexes and age groups and thereby serve an important function in population dynamics.
The annual cycle of migrants is typically divided into four fundamental periods: the breeding season, autumn migration, the wintering period, and vernal migration (Helms 1963). Each phase comprises distinct physiological and behavioral characteristics and each has unique properties with respect to the complex life histories of migrants. In general, more research emphasis has been placed on the breeding and migration periods compared to the winter period (e.g., Berthold 1988a). The overall winter distributions of many migrant species are well known, but detailed analyses of population structure, ecology, and physiology during this period are scarce.
Avian migration varies considerably both inter- and intraspecifically with respect to direction, timing and distance (Schüz 1971 ; Gauthreaux 1982). In populations of differential migrants all individuals migrate, but they differ in timing or distances (e.g., Gauthreaux 1982; Ketterson and Nolan 1983). Many species consist of breeding populations which reflect differential migratory behavior to the extent that some individuals migrate while others do not (Schüz 1971). This situation is referred to as partial migration (Schüz and Meise 1968). The définition should not be used for species that migrate in part of their breeding range and are sedentary elsewhere (Terrill and Able 1988).
Effects of daily changes in weather on numbers of birds taking off on migration have been investigated for many decades. This field was especially active in the 1960s and 1970s when many systematic radar and visual studies of migration were done. Also, multivariate and other statistical methods became widely used, providing a partial solution to the problem of quantifying and separating the effects of interrelated weather variables on migration. Work up to 1977 was reviewed by Richardson (1978a), hereafter cited as R78a.
Relationships of short-term weather to daily migration intensity are reviewed, with sections for each weather variable, for waterfowl, shorebirds and hawks, and for reverse migration. Selecting factors, methodology, hypotheses and results to date are summarized, generalizations about migration-weather relationships are extracted from the pooled results, and high-priority research topics are identified. Ultimate factors responsible for present responses are thought to include aspects of weather en route and a the take-off point and destination. Proximate factors affecting the probability of take-off may include variables useful in predicting, as well as those that measure, aspects of weather with selective significance. Causative and coincidental relationships remain difficult to separate, and at least a few birds migrate in almost any weather conditions. However, maximum numbers migrate with fair weather, with tailwinds and with temperature, pressure and humidity conditions that accompany tailwinds. Correlations with weather differ among populations with different flight directions. General patterns of responses appear to be modified by special selecting factors that apply to certain groups - soaring hawks tend to fly on days with strong updrafts, landbirds migrating along coasts prefer onshore to offshore winds, and transients in unsuitable habitats seem less likely to wait for favourable travelling conditions. /// дан обзор взаимосвязи погодных усповий и иитенсивности суточных миграпий с раздепами, посвященными анализу впияния отдельных погодных факторов на миграции водоплавающих, береговых и хищных птиц и на обратные мнграции. Обобщены сепеютирукщие факторы, методопогия, гипотезы и результаты, имеющиеся в настоящее время, сдепаны выводы о взаимосвязях миграции-погода, на основании имеющихся материапов определены генералвные направюения иччледований. Предполагается, что ультимативные фактопы, определяющие эти отношения, включают характер погоды по маршруту миграции, а также в точках отлета и назначения. Непосредственное влияние на отлет могут оказывать различные аспекты погоды, которые можно измерить ипи предсказать: отдельные факторы имеюь различную значимость. Причинные и сопутсвующие связи трудно разделить и, по крайней мере, некоторые птицы мигрируют при погодных условиях. Однако, максимальное количество птиц мигрирует при хорошей погоде, попутном ветре и соответствующих температурах, атмосферном давлении и влажности. Основной характер взаимосвязей может модифицироваться специальными фактояами, которые имеюь значение для некоторых хищников, парящих группами и предпочитающих дни с сильными вертикальными токами, а также у сухопутных птиц, мигрирующих вдопь берега и предпочитающих ветер с моря береговому бризу, и наконец, у перелетных птиц, оказывающихчя на пролете в неподходящих местообитаниях, которые не дожидаются наиболее благоприятных условий для перелета.
To evaluate hypotheses explaining intraspecific variation in migratory behavior in partial migrants, a local population of Blue Tits (Parus caeruleus) was studied in southern Sweden. Birds born in the study area and recaptured there in winter were compared with birds recaptured at a nearby bird station where a large number of migrant Blue Tits were passing. By comparing sex ratios among migrants and residents, we concluded that, among juveniles, more than 40% of the females and a significant proportion of the males migrated, while
considerably fewer adult females and virtually no adult males did so. Migrant and resident Blue Tits did not differ in size as nestlings, but more late- than early-hatched males migrated. No differences in hatching date were determined for females, presumably because most of them migrated. Our findings are consistent with the "dominance hypothesis" as an explanation of partial migration, i.e. that the individuals lowest in rank migrate. The fitness gain that leads dominants to stay as residents may be lower winter mortality or a higher probability of establishing a territory in spring. In either case, keener competition for breeding territories among
males than among females as a cause for higher residency cannot be excluded.
A sample of 22 radio-tagged male Great Bustards from central Iberian populations was studied from 1996 to 1998. All birds undertook seasonal movements to postbreeding
areas located up to 167 km away from their leks. Departures from leks occurred between
May and July, with most birds moving northeast to summering areas. Approximately 47% of
the males spent only the summer away from their leks, returning to leks between September
and December. Other males overwintered in areas located to the southeast, returning to lek
sites between January and March.
Recent evidence suggests that facultative behavioural and physiological patterns in birds are triggered by unpredictable environmental events such as severe storms. These facultative patterns may involve finding a refuge ('shelter') until the perturbation passes, leaving the area and seeking other suitable habitat (e.g. irruptive-type migration), or a combination - seek a refuge at first and then if conditions remain inclement, seek other habitat. All these facultative events require that the individual retain sufficient fat reserves to either shelter ('ride-out') from the storm, leave a home range and forage nearby or, if suitable habitat is unlikely to be found close at hand, to fuel a flight of tens to hundreds of kilometers. Laboratory experiments in White-crowned Sparrows Zonotrichia leucophrys indicate that negative energy balance such as when a storm or other perturbation decreases food availability or intake, increased secretion of corticosterone. This in turn activates escape-like behaviour consistent with irruptive-type migration. Field studies confirm that elevated levels of corticosterone during inclement weather correlate with abandonment of nest sites in several species of sparrow, movements away from winter ranges when snow covers food resources, and alter movement patterns in seabirds. The steroid hormone corticosterone may play a major role in orchestrating facultative behavioural and physiological patterns (i.e. an 'emergency life history stage') to a variety of environmental perturbations. The resulting local movements, or irruptive migrations, are thus a form of facultative dispersal that may serve to maximize survival in the face of unpredictable and deleterious events in the environment.
1. In southern France breeds an obligate partially migratory population of the Blackcap with about three quarters of migrants and one quarter of residents. Partial migration of this population is considerably controlled by genetic factors (Berthold &Querner 1982). The large selection response of a two-way selective breeding experiment up to F1-generations suggested a high evolutionary potential of obligate partial migration (2). We have this evolutionary potential experimentally investigated in a long-term selective breeding study.
2. We raised by hand a total of 267 individuals of the free-living Blackcap population in five groups, and all five samples showed corresponding ratios of migrants and nonmigrants. We were able to conduct the long-term selective breeding experiment up to a F6-generation, and thereby a total of 455 Blackcaps could be bred in aviaries.
3. The two-way selective breeding experiment shows, that the investigated partially migratory Blackcap population can become completely migratory in just three generations and almost exclusively sedentary in just four to six generations.
4. The two-way selective breeding experiment yielded large selection responses and high heritability values (about 0.6–1) which are distinctly higher than those previously reported for behavioural traits of (mostly domesticated) vertebrates. Hence, genetic factors are very important for the control of this obligate partial migration and are presumedly dominant over environmental influences.
5. In case of rapid environmental changes and the effect of strong selection factors the experimental results suggest a strikingly high evolutionary potential of obligate partial migration and thus in general a rapid microevolution of bird movements. If climatic changes would occur in the near future as they are predicted by meteorologists (rise in temperature due to man-made pollution of the atmosphere, “greenhouse-effect”) then many obligate partial migrants could rapidly become sedentary on a genetic basis and many less typical migrants could then considerably suffer from the general increase of residents.
6. A genetic control of obligate partial migration appears to be widespread and it also appears to be the most reliable control mechanism for all individuals of such a partially migratory population. Facultative partial migration, however, appears to be controlled more directly by environmental factors.
Im Winter 1969/70 fand ein besonders starker Einflug der Großtrappe (Otis tarda L.) nach West-Europa statt. Daran dürften etwa 300 Vögel beteiligt gewesen sein, von denen mindestens der überwiegende Teil aus der DDR stammte, und die hauptsächlich in Nordwestdeutschland und in Holland auftraten; Einzelexemplare flogen bis Bayern, Frankreich, Schottland und Dänemark. Nach den Einflügen bei strengem Frost und hoher Schneelage im Dezember und Januar führten die überwinternden Großtrappen witterungsabhängige, zwischen W und E pendelnde, Wanderungen aus, die typische Randzugerscheinungen darstellten. Auf dem Rückzug bildete sich im März im östlichen Niedersachsen ein Zugstau aus. Die Großtrappen zeigten sich meistens einzeln, mehrfach jedoch auch in Trupps bis zu 5, gelegentlich bis zu 20 Exemplaren. Das Geschlechterverhältnis betrug 1 ♂ : 1,35 ♀. Etwa 10% der eingeflogenen Großtrappen kamen um. Da nicht jeder strenge Winter so ausgedehnte Großtrappenwanderungen in Mitteleuropa bewirkt, dürfte die Ursache für den Einflug 1969/70 das ganz besonders frühe Einsetzen winterlicher Witterung gewesen sein, so daß ein latent vorhandener Wegzugtrieb noch ausgelöst werden konnte.
Zur Bestandssituation der Großtrappe
- Dornbusch
Investigations into the nutrition of the Great Bustard (Otis tarda L.) in the winter aspect of 1977/78
- Sterbetz
Bestand, Bestandsförderung und Wanderungen der Großtrappe (Otis tarda)
- M Dornbusch
Multivariate analyses of weather and fall migration of Saw-Whet Owls at Duluth, Minnesota
- D L Evans
- DL Evans
Schutz und Hege der Großtrappe Otis tarda L
- G Klafs
A note on the invasion of western Europe by the Great Bustard in the winter seasons
- D Hummel
Die Großtrappe (Otis tarda L.) Gegenwartsprobleme und Rettungsmöglichkeiten
- O Koenig
Naturschutz und Landwirtschaft im Großtrappenschongebiet Buckow
- H Litzbarski
- D Eichstädt
Zur Ökologie und zum Schutz der Großtrappe (Otis tarda L.) im Bezirk Potsdam
- B Litzbarski
- H Litzbarski
- S Petrick
Bestandsentwicklung, Ökologie und Schutz der Großtrappe (Otis tarda L.) in der Notte-Niederung
- B Ludwig
Zur Situation der Großtrappe Otis tarda in Deutschland
- H Litzbarski
- B Litzbarski
Die Entwicklung der Großtrappenbestände unter den Bedingungen des Bezirkes Potsdam
- H Litzbarski
- M Loew
Bustard specialist group
- K Nelson
Control of partial migration and autumnal behavior Bird migration. Physiology and ecophysiology
- H Schwabl
- B Silverin
Investigations into the nutrition of the Great Bustard (Otis tarda L.) in the winter aspect of
- I Sterbetz
Vogelkundliche Beiträge aus dem Neusiedlerseegebiet
- R Triebl
Wiederfunde von in Buckow ausgewilderten Großtrappen (Otis t. tarda L., 1758)
- B Block
Family Otidiae (Bustards)
- N J Collar
- NJ Collar
Naturschutz und Landwirtschaft im Großtrappenschongebiet Buckow, Kreis Rathenow
- H Litzbarski