Migration, wintering and breeding of a lesser spotted eagle ( Aquila pomarina) from Slovakia tracked by satellite

In northern Slovakia an adult male Lesser Spotted Eagle (Aquila pomarina) occupied the same nest site for 11 years running (1992–2002), where it was ringed and fitted with two satellite transmitters. In six of these years it successfully reared a young. In 1994 and 2000–2002 its behaviour during migration could be followed in detail by means of satellite telemetry. The eagle took the known route for this species to South Africa. In 2001, it spent 43% of the year at its breeding site, 33% in its winter quarters, the remaining 24% being spent on migration. In three cases the autumn migration took 40, 48 and 61 days respectively. In two cases the spring migration took 49 days. All five recorded autumn and spring migrations averaged a daily flight distance of 178 km. In spring the daily flight distance was in general slightly greater than in autumn. The longest was recorded from 30 March to 2 April 2001, between Uganda and the Red Sea, during which the bird covered a total of 1,650 km, averaging 412 km per day. In 2001, the spring migration from the wintering grounds was 2 weeks later than in 2002. The wintering grounds, where in 2 years the bird spent around 3.5 months, covering at least 1,666 and 2,269 km, respectively, comprised a large part of Zimbabwe together with the Kruger National Park in South Africa and neighbouring parts of Mozambique. The annual journeys flown, including movements around the wintering grounds, amounted in 2000-2001 to at least 20,396 km and in 2001-2002 to 19,041 km. Except during its crossing of the Sahara, the eagle must have taken food on nearly all its days of migration.     

Comparative migration strategies of wild and captive‐bred Asian Houbara Chlamydotis macqueenii

For migratory species, the success of population reintroduction or reinforcement through captive‐bred released individuals depends on survivors undertaking appropriate migrations. We assess whether captive‐bred Asian Houbara Chlamydotis macqueenii from a breeding programme established with locally sourced individuals and released into suitable habitat during spring or summer undertake similar migrations to those of wild birds. Using satellite telemetry, we compare the migrations of 29 captive‐bred juveniles, 10 wild juveniles and 39 wild adults (including three birds first tracked as juveniles), examining migratory propensity (proportion migrating), timing, direction, stopover duration and frequency, efficiency (route deviation), and wintering and breeding season locations. Captive‐bred birds initiated autumn migration an average of 20.6 (±4.6 se) days later and wintered 470.8 km (±76.4) closer to the breeding grounds, mainly in Turkmenistan, northern Iran and Afghanistan, than wild birds, which migrated 1217.8 km (±76.4), predominantly wintering in southern Iran and Pakistan (juveniles and adults were similar). Wintering locations of four surviving captive‐bred birds were similar in subsequent years (median distance to first wintering site = 70.8 km, range 6.56–221.6 km), suggesting that individual captive‐bred birds (but not necessarily their progeny) remain faithful to their first wintering latitude. The migratory performance of captive‐bred birds was otherwise similar to that of wild juveniles. Although the long‐term fitness consequences for captive‐bred birds establishing wintering sites at the northern edge of those occupied by wild birds remain to be quantified, it is clear that the pattern of wild migrations established by long‐term selection is not replicated. If the shorter migration distance of young captive‐bred birds has a physiological rather than a genetic basis, then their progeny may still exhibit wild‐type migration. However, as there is a considerable genetic component to migration, captive breeding management must respect migratory population structure as well as natal and release‐site fidelity.     

The role of herbivorous water birds in aquatic systems through interactions with aquatic macrophytes,with special reference to the Bewick’s Swan – Fennel Pondweed system

The role of aquatic macrophytes in stimulating biodiversity and maintaining clear waters is currently undisputed. The management of (eutrophic) shallow waters is therefore often directed at (re-)establishing macrophyte domination. In contrast, the role of water birds has long been considered of minor importance for the functioning of fresh water ecosystems. Indeed, in terms of biomass and production, water birds constitute only a minor part of these systems. However, water birds may graze heavily on water plants under certain circumstances, and the question arises whether herbivorous water birds have an important indirect effect on shallow fresh water systems. Mainly illustrated with the interaction between Bewick’s Swans and Fennel Pondweed, we present data on the role that water plants may play in the life of water birds and how water birds may impact water plants’ fitness in terms of survival, production, dispersal and competitive ability. It appears that water plants may be crucial for water birds during periods of high-energy requirements, such as migration. Despite the plants’ costs associated with water bird grazing, the interaction between water birds and water plants varies in nature from an apparent predator–prey relationship to a mutually beneficial interaction depending on the context and the perspective. For the case of the Bewick’s Swan–Fennel Pondweed interaction, regular bird grazing is sustainable and may actually favour the plant’s dispersal. Thus, Bewick’s Swans themselves may in fact play a crucial role in establishing and maintaining the Fennel Pondweed rich staging sites between the swans’ wintering and breeding grounds, which are vital for the swans’ successful migration.     

Autumn migration and wintering of northern fulmars (<Emphasis Type="Italic">Fulmarus glacialis</Emphasis>) from the Canadian high Arctic

Five northern fulmars (Fulmarus glacialis) were tracked by satellite transmitters from their breeding colony in the Canadian high Arctic (Cape Vera, Devon Island, NT) to their wintering grounds in the northwest Atlantic Ocean. In both 2004 and 2005, fulmars left northern Baffin Bay in mid- to late September, and migrated south to Davis Strait in less than 1 week, after which movements were erratic. In October and November, the birds were widely distributed, but by December through March, they tended to remain in the Labrador Sea between 50 and 55°N. Average flight speed was 35 km/h with a maximum of 64 km/h, and over their entire transmission periods, the five traveled on average 84 km/day. Our work suggests that the North Atlantic northern fulmar population may be panmictic in winter, with the Labrador Sea as a key wintering site for fulmars from high Arctic Canada.     

Satellite tracking of Swedish Ospreys Pandion haliaetus: autumn migration routes and orientation

Autumn migration routes and orientation of Swedish Ospreys Pandion haliaetus were studied by satellite tracking of 18 birds. Of these, 13 could be followed during the entire migration (6 females, 5 males and 2 juveniles). Most birds migrated across western and central Europe to winter in tropical West Africa. However, one juvenile flew to Cameroon and one female used a very easterly route and reached Mozambique. On average, the birds travelled a total distance of about 6700 km, with little variation except for the female wintering in Mozambique, who travelled more than 10 000 km. Of 21 stopovers (of >1 day), only five were made south of 45°N; three of these in Africa. Females departed before males and juveniles and flew to a stopover site they probably were familiar with. After 3–4 weeks there, they continued to their wintering grounds. Also males and juveniles usually made one or more stopovers. Adults seemed to travel to a known wintering site, where they remained stationary, whereas juveniles were more mobile after reaching tropical regions, probably looking for good wintering sites. Males generally left the breeding area in directions similar to the mean migratory direction, whereas a few females departed in diverging initial directions. Apart from these diversions, adult Ospreys followed very straight migratory routes, with overall mean directions of 185–209° and with mean angular deviations of 6–33°. Some juveniles also departed in diverging directions. Moreover, young birds tended to show a larger variability in orientation. Thus, the Ospreys kept a fairly straight direction and did not avoid geographical obstacles such as mountain ranges and desert areas. However, they seemed reluctant to cross large water bodies. There was no correlation between angular deviation and length of the migrational segment, indicating that the principles of orientation by vector summation may not be valid for Osprey migration. Moreover, the geographic direction of migration did not vary in accordance with variations in the magnetic declination, suggesting that the Ospreys did not orient along magnetic loxodromes.     

Factors influencing diet variation in a generalist predator across its range distribution

Factors linked with intraspecific variation in trophic diversity are still poorly understood in generalist species like the Montagu’s harrier (Circus pygargus) but may have important implications for conservation management at a wide scale. We described geographic patterns of Montagu’s harrier diet across Eurasia, gathering diet data from 30 studies in 41 areas from 11 countries. We grouped prey as invertebrates, reptiles, small mammals, large mammals, eggs, small birds and large birds, and calculated the contribution of each prey type to the diet (as % biomass) and Shannon’s Diversity Index for each study site. We analysed qualitative estimates of prey abundance in relation to latitude and longitude, then diet composition in relation to habitat of the study area and prey abundance estimates. Diet diversity of Montagu’s harriers increased from north to south, while abundance of all prey groups other than small mammals showed the opposite trends. Agricultural areas in northern latitudes seemed to hold high densities of small mammals, but low densities of alternative prey. Overall, birds were the main prey in most of Montagu’s harrier’s distribution range, although the relative importance of each prey type in the diet was significantly explained by its local abundance and habitat, confirming the opportunistic foraging strategy of this raptor species. Consumption of mammals was an exception to this trend, being negatively associated with the abundance of alternative prey, suggesting that this prey is not preferred. Trophic diversity in this species could be influenced by land-use changes through variations in the abundance and availability of prey, which could impact its population dynamics. This may be particularly important for northern populations of Montagu’s harriers breeding in agricultural habitats, where trophic diversity is already low.     

基于卫星跟踪大天鹅春季迁徙时间及其影响因素

候鸟春季迁徙时间与其能否顺利完成迁徙过程,以及对繁殖地的成功选择和繁殖成效密切相关,通过对大天鹅越冬地和停歇地的春季迁徙时间选择原因及其影响因素进行分析,有助于深入理解候鸟春季迁徙时间策略和栖息地保护状况。2015年2月和12月,在河南三门峡湿地捕捉了60只越冬大天鹅并佩戴卫星跟踪器,获取了详细的大天鹅在越冬地和停歇地的春季迁徙时间等信息,并进一步分析了春季迁徙时间与气候因子的相关性。结果表明,大天鹅主要在夜间22：00-0：00和0：00-1：59迁离越冬地。大天鹅迁离越冬地的日期与温度呈显著性正相关,迁离时多选择顺风且风速较小的天气。大天鹅迁离越冬地后主要是在夜间飞行,而迁离停歇地后主要是在日间飞行。越冬地的温度越高,越有利于植物的生长,大天鹅可以快速地积累能量,提前开始春季迁徙。野外调查表明,内蒙古黄河中上游作为迁徙的重要停歇地,春季两岸捕鱼、农耕和放牧等为活动较多,因此大天鹅多选择在夜间觅食补充能量,在日间迁离。最后,针对黄河流域大天鹅栖息地的保护现状,提出了禁止经济开发项目、建立保护区和开展宣传教育等保护建议。     

Spring migratory routes and stopover duration of satellite‐tracked Eurasian Teals Anas crecca wintering in Italy

Identifying an organism's migratory strategies and routes has important implications for conservation. For most species of European ducks, information on the general course of migration, revealed by ringing recoveries, is available, whereas tracking data on migratory movements are limited to the largest species. In the present paper, we report the results of a tracking study on 29 Eurasian Teals, the smallest European duck, captured during the wintering period at three Italian sites. The departure date of spring migration was determined for 21 individuals, and for 15 the entire spring migratory route was reconstructed. Most ducks departed from wintering grounds between mid‐February and March following straight and direct routes along the Black Sea‐Mediterranean flyway. The breeding sites, usually reached by May, were spread from central to north‐Eastern Europe to east of the Urals. The migratory speed was slow (approximately 36 km/day on average) because most birds stopped for several weeks at stopover sites, mainly in south‐eastern Europe, especially at the very beginning of migration. The active flight migration segments were covered at much higher speeds, up to 872 km/day. Stopover duration tended to be shorter when birds were closer to their breeding site. These results, based on the largest satellite tracking effort for this species, revealed for the first time the main features of the migratory strategies of individual Teals wintering in Europe, such as the migration timing and speed and stopover localization and duration.     

Satellite tracking of two Montagu’s Harriers (Circus pygargus): dual pathways during autumn migration

Autumn migration routes of two Dutch female Montagu’s Harriers (Circus pygargus) were documented for the first time using satellite telemetry. Both migrated to their African wintering area—one via the Straits of Gibraltar through the Mediterranean and the other via Italy/Tunisia. The rate of travel was comparable to values reported for larger raptor species.