Survival and reproduction of adult snowy owls tracked by satellite

Satellite telemetry can provide valuable information on spatial ecology of animals, especially in species inhabiting remote areas such as the Arctic. However, caution is always needed when selecting transmitter size and attachment methods because of the potential negative impact of the device itself on individuals. We determined survival and reproductive performance of adult female snowy owls (Bubo scandiacus) tracked by satellite to evaluate potential adverse effects of transmitters. In summer 2007, we captured 12 adult females on their nest in the Canadian Arctic, marked them with 30-g harness-mounted transmitters, and tracked their movement for up to 3 years. All marked birds resumed normal activities shortly (<60 min) after release and none deserted their nest. We had 2 known deaths and 2 transmitters that stopped moving over 3 years, yielding an annual survival rate between 85.2 ± 7.0% and 92.3 ± 5.7%. Moreover, summer movement patterns, combined with ground checks in several cases, suggested that all successfully tracked birds initiated a nest every year after marking. Finally, laying date and clutch size of individuals did not differ before and after marking. Overall, our data indicate that life history traits of adult female snowy owls were not affected by satellite transmitters. © 2012 The Wildlife Society.     

Movements and foraging effort of Steller's Eiders and Harlequin Ducks wintering near Dutch Harbor, Alaska

ABSTRACT.   We studied the movements and foraging effort of radio-marked Steller's Eiders ( Polysticta stelleri ) and Harlequin Ducks ( Histrionicus histrionicus ) to evaluate habitat quality in an area impacted by industrial activity near Dutch Harbor, Alaska. Foraging effort was relatively low, with Steller's Eiders foraging only 2.7 ± 0.6 (SE) hours per day and Harlequin Ducks 4.1 ± 0.5 hours per day. Low-foraging effort during periods of high-energetic demand generally suggests high food availability, and high food availability frequently corresponds with reductions in home range size. However, the winter ranges of Harlequin Ducks did not appear to be smaller than usual, with the mean range size in our study (5.5 ± 1.1 km²) similar to that reported by previous investigators. The mean size of the winter ranges of Steller's Eiders was similar (5.1 ± 1.3 km²), but no comparable estimates are available. Eutrophication of the waters near Dutch Harbor caused by seafood processing and municipal sewage effluent may have increased populations of the invertebrate prey of these sea ducks and contributed to their low-foraging effort. The threat of predation by Bald Eagles ( Haliaeetus leucocephalus ) that winter near Dutch Harbor may cause Steller's Eiders and Harlequin Ducks to move further offshore when not foraging, contributing to an increase in range sizes. Thus, the movement patterns and foraging behavior of these ducks likely represent a balance between the cost and benefits of wintering in a human-influenced environment.     

Age-dependent migration strategy in honey buzzards Pernis apivorus tracked by satellite

Six adult and three juvenile honey buzzards Pernis apivorus were radio-tracked by satellite during autumn migration from southwestern Sweden. All adults crossed the Mediterranean Sea at the Strait of Gibraltar and continued across the Sahara desert to winter in West Africa, from Sierra Leone to Cameroon. Analysing three main steps of the migration, (1) from the breeding site to the southern Mediterranean region, (2) across the Sahara and (3) from the southern Sahara to the wintering sites, the adults changed direction significantly between these steps, and migrated along a distinct large-scale detour. In contrast, the juveniles travelled in more southerly directions, crossed the Mediterranean Sea at various places, but still ended up in the same wintering areas as the adults. Average speeds maintained on travelling days were similar for the two age groups, about 170 km/day in Europe, 270 km/day across Sahara and 125 km/day in Africa south of Sahara. However, as the adults used fewer stopover days en route, they maintained higher mean overall speeds and completed migration in a shorter time (42 days) than the juveniles (64 days). Although the juveniles set out on more direct courses towards the wintering grounds, they did not cover significantly shorter distances than the adults, as they tended to show a larger directional scatter between shorter flight segments. The results corroborate previous suggestions that adult and juvenile honey buzzards follow different routes during autumn migration, and that the birds change migration strategy during their lifetime. While juveniles may use individual vector orientation, social influences and learning may be of great importance for the detour migration of adults. The remarkable and distinct age-dependent shift in migratory route and orientation of the honey buzzard provides a challenging evolutionary problem.     

Movements and landscape use of Eastern Imperial Eagles Aquila heliaca in Central Asia

Capsule: We describe ecological factors associated with movements of a globally declining raptor species, the Eastern Imperial Eagle Aquila heliaca.

Aims: To describe the movements, habitat associations and resource selection of Eastern Imperial Eagles marked in Central Asia.

Methods: We used global positioning system (GPS) data sent via satellite telemetry devices deployed on Eastern Imperial Eagles captured in Kazakhstan to calculate distances travelled and to associate habitat and weather variables with eagle locations collected throughout the annual cycle. We also used resource selection models to evaluate habitat use of tracked birds during autumn migration. Separately, we used wing-tagging recovery data to broaden our understanding of wintering locations of eagles.

Results: Eagles tagged in Kazakhstan wintered in most countries on the Arabian Peninsula, as well as Iran and India. The adult eagle we tracked travelled more efficiently than did the four pre-adults. During autumn migration, telemetered eagles used a mixture of vegetation types, but during winter and summer, they primarily used bare and sparsely vegetated areas. Finally, telemetered birds used orographic updrafts to subsidize their autumn migration flight, but they relied on thermal updrafts during spring migration.

Conclusion: Our study is the first to use GPS telemetry to describe year-round movements and habitat associations of Eastern Imperial Eagles in Central Asia. Our findings provide insight into the ecology of this vulnerable raptor species that can contribute to conservation efforts on its behalf.     

Growth and demography of a re‐introduced population of White‐tailed Eagles Haliaeetus albicilla

White‐tailed Eagles Haliaeetus albicilla became extinct in Britain in 1918 following prolonged persecution. Intensive conservation efforts since the 1970s have included the re‐introduction of the species to Britain through two phases of release of Norwegian fledglings in western Scotland in 1975–85 and 1993–98. Population growth and breeding success have been monitored closely to the present day, aided by the use of patagial tags to individually mark most released birds as well as a high proportion of wild‐bred nestlings. This study reviews the growth and demography of this re‐introduced population, and makes comparisons with other European populations. For the first time, we compare the demographic rates of released and wild‐bred birds in the Scottish population. Breeding success in the Scottish population has increased over time as the average age and experience of individuals in the population have increased, and success tends to be higher where one or both adults are wild‐bred. Current levels of breeding success remain low compared with some other populations in Europe, but similar to those in Norway where weather conditions and food availability are likely to be most similar. Survival rates in Scotland are similar to those recorded elsewhere, but survival rates of released birds are lower than those of wild‐bred birds, especially during the first 3 years of life. Despite the effect of lower survival rates of released birds in limiting overall population growth rate, the recent rate of growth of the Scottish population remains high relative to other recovering populations across Europe. Differences in demographic rates of wild‐bred and released birds suggest that in future re‐introduction programmes, steps to maximize the success and output of the earliest breeding attempts would help ensure the most rapid shift to a population composed largely of wild‐bred birds, which should then have a higher rate of increase.     

Phylogenetic Position of Mammoth and Steller's Sea Cow Within Tethytheria Demonstrated by Mitochondrial DNA Sequences

Here we report DNA sequences from mitochondrial cytochrome b gene segments (1,005 base pairs per species) for the extinct woolly mammoth (Mammuthus primigenius) and Steller's sea cow (Hydrodamalis gigas) and the extant Asian elephant (Elephas maximus), the Western Indian manatee (Trichechus manatus), and the hyrax (Procavia capensis). These molecular data have allowed us to construct the phylogeny for the Tethytheria. Our molecular data resolve the trichotomy between the two species of living elephants and the mammoth and confirm that the mammoth was more closely related to the Asian elephant than to the African elephant. Our data also suggest that the sea cow–dugong divergence was likely as ancient as the dugong–manatee split, and it appears to have been much earlier (22 million years ago) than had been previously estimated (4–8 million years ago) by immunological comparison. Received: 8 August 1996 / Accepted: 30 September 1996     

Inter- and intra-specific dominance relationships and feeding behaviour of Golden Eagles Aquila chrysaetos and Sea Eagles Haliatetus albicilla at carcasses

The behaviour of Golden Eagles Aquila chrysaetos and Sea Eagles Haliceetus albicilla scavenging on artificially laid out carcasses in coastal Sør-Trøndelag Province, Norway, was studied during two winters (totalling 640 h of observations) and the intervening summer (430 h). Neither species fed at carcasses in summer. Although smaller, Golden Eagles were strongly dominant over Sea Eagles in direct competition for carcass access. In Sea Eagles, females dominated males, while in Golden Eagles, few conflicts between birds of known sex were observed. Age effects were weak and not statistically significant in both species. Conflicts for carcass access tended to be most escalated between Golden Eagles and least escalated between Sea Eagles, with interspecific conflicts intermediate. Most conflicts were won by the aggressor, suggesting that birds were generally able to assess relative dominance before launching an attack. Young eagles fed longer at a carcass than older individuals in both species, suggesting that young eagles may have been hungrier or less efficient feeders. Sea Eagles waited longer than Golden Eagles between arrival in the immediate carcass area and feeding at the carcass. This effect was greater when the carcass was already occupied but also occurred when no other eagle was already present. While interspecific competition for carrion did not appear to have important consequences for the two species in coastal Norway, in western Scotland, where Sea Eagles are currently re-establishing, carrion is important in the diet of both species all year round. Interspecific competition for this resource may therefore play a role in determining the ultimate realized niche (and therefore numbers) of the two species in Scotland in the longer term.     

Bonelli's Eagle Hieraaetus fasciatus juvenile dispersal: hourly and daily movements tracked by GPS

Capsule Birds cover daily distances not normally exceeding 20 km during the initial phase of dispersal, with the daily peak of movement/activity in the afternoon.     

Spatial,seasonal and individual variation in the diet of White‐tailed Eagles Haliaeetus albicilla assessed using stable isotope ratios

Many raptor species are considered to be generalists, taking a range of prey species. However, longitudinal dietary records are often scarce, although necessary for characterizing niche width of species at population and individual levels. Quantifying raptor diets at large spatio‐temporal scales is often necessary for refining conservation efforts, although it can be particularly difficult and may involve a great effort by conventional means. Therefore, we adopted the analysis of stable isotopes in tissues of predators and their potential food sources as a complementary methodology for assessing animals' diet. We examined the isotopic composition (δ¹³C and δ¹⁵N) of White‐tailed Eagles Haliaeetus albicilla from Germany, Finland and Greenland to detect patterns of dietary variation and quantify diet composition. The isotopic analysis included liver and muscle samples from Eagles of the three populations together with 16 potential food sources in the German population. Our results suggested dietary differences between German and Greenlandic Eagles, in accordance with the availability of freshwater and marine habitats in each population. Within the German population, we found seasonal shifts in isotopic ratios, suggesting the birds responded to temporal changes in food availabilities, and age‐related isotopic differences, indicating different diets in adults and juveniles. Isotopic values of liver and muscle tissues collected from the same animal showed intra‐individual short‐term changes in the German and Finnish but not Greenlandic population. This suggests that local feeding niches of this generalist predator may vary with local food supplies, which determines the niche width (from generalist to specialist) at the individual level. Our results also revealed that game mammal carcasses constitute an important food source (29.5% of diet) for the German Eagle population during the winter half‐year corresponding to the hunting season. This result is of relevance to management and conservation because the White‐tailed Eagle and other raptor species are affected by the ingestion of lead ammunition from shot mammalian carcasses.     

Movements and habitat use by immature Cinereous Vultures (Aegypius monachus) from the Caucasus

Capsule Juvenile and immature Cinereous Vultures from the Caucasus move large distances across undeveloped open-dry habitats in response to snowfall or high summer temperatures.

Aim To study local and long-range movements of Cinereous Vulture (Aegypius monachus), and investigate the influence of environmental variables on spatial and temporal distributions of the species on a large scale.

Methods We use 4-year-long location data from 6 juvenile Cinereous Vultures fitted with satellite-received transmitters to track their movements and obtain habitat suitability models.

Results A few months after fledging, Cinereous Vultures may migrate from the Caucasus as far south as the Arabian Peninsula. Their movements are concentrated in undeveloped open-dry habitats. High temperatures push the vultures to higher latitudes and altitudes, while reverse seasonal movements are triggered by the extent of snow cover.

Conclusions Our study shows the importance of the Arabian Peninsula and Iran as wintering areas for Cinereous Vultures. Long-distance movements by immature cinereous vultures are determined by climate seasonality, and in light of climate-warming scenarios for the next 100 years, there might be a shift in timing of the onset of the species seasonal movements and a change in the duration and geography of its wintering and summering.     

Migrations and sojourn in Africa of Egyptian vultures ( Neophron percnopterus) tracked by satellite

By means of satellite telemetry, the migrations of three young Egyptian vultures (Neophron percnopterus) from France and Bulgaria were studied and data obtained (over 4,300 Argos locations) to describe movement patterns, timing of migration, routes followed, speed of flight and ranging behaviour in Africa. Two French vultures migrated at almost the same time and, after travelling ca. 3,570 km, remained in the Sahelian zone, in southern Mauritania. The Bulgarian bird, after travelling 5,340 km, ended in south-east Chad, in the Sudano-Sahelian zone. It was possible to determine two remarkably long daily flight distances of this bird of over 500 km on two successive days (1,017 km in total) when crossing the Sahara. In January and February, the Bulgarian bird wandered extensively over 2,600 km, even as far as north-east Nigeria. Both French vultures remained in their home ranges in Mauritania once they had adopted them, which extended to 69,000 km² and 50,000 km², respectively. One continuously-tracked vulture from France first left its African home range when 3 years old (probably in its fourth plumage type).Communicated by F. Bairlein     

First description of migration and wintering of adult Egyptian Vultures Neophron percnopterus tracked by GPS satellite telemetry

Capsule Over two years birds showed high territorial and high winter site fidelity in the Sahel.     

The diet of the Sea Eagle Haliaeetus albicilla and Golden Eagle Aquila chrysaetos in western Scotland

The diets of Sea Eagles Haliaeetus albicilla and Golden Eagles Aquila chrysaetos living sympatrically in western Scotland were studied using pellets and prey remains collected at roosts and nest sites throughout the year. Both species showed changes in diet between winter and summer, and there were differences between species in both seasons. As a rule, Sea Eagles took proportionately more seabirds, waterfowl (ducks and waders) and fish, whilst Golden Eagles took proportionately more rabbits and hares. Sea Eagles had a broader diet than Golden Eagles but a measure of dietary overlap based on taxonomic composition indicated an overlap of more than 90% between the two species.     

Breeding and moulting locations and migration patterns of the Atlantic population of Steller's eiders Polysticta stelleri as determined from satellite telemetry

This study was designed to determine the spring, summer, autumn, and early winter distribution, migration routes, and timing of migration of the Atlantic population of Steller's eiders Polysticta stelleri . Satellite transmitters were implanted in 20 eiders captured in April 2001 at Vadsø, Norway, and their locations were determined from 5 May 2001 to 6 February 2002. Regions where birds concentrated from spring until returning to wintering areas included coastal waters from western Finnmark, Norway, to the eastern Taymyr Peninsula, Russia. Novaya Zemlya, Russia, particularly the Mollera Bay region, was used extensively during spring staging, moult, and autumn staging; regions of the Kola, Kanin, and Gydanskiy peninsulas, Russia, were used extensively during spring and moult migrations. Steller's eiders migrated across the Barents and Kara seas and along the Kara Sea and Kola Peninsula coastal waters to nesting, moulting, and wintering areas. The majority of marked eiders (9 of 15) were flightless in near-shore waters along the west side of Novaya Zemlya. Eiders were also flightless in northern Norway and along the Kanin and at Kola Peninsula coasts. We compare and contrast natural history characteristics of the Atlantic and Pacific populations and discuss evolutionary and ecological factors influencing their distribution.     

Breeding and moulting locations and migration patterns of the Atlantic population of Steller's eiders Polysticta stelleri as determined from satellite telemetry

This study was designed to determine the spring, summer, autumn, and early winter distribution, migration routes, and timing of migration of the Atlantic population of Steller's eiders Polysticta stelleri. Satellite transmitters were implanted in 20 eiders captured in April 2001 at Vadsø, Norway, and their locations were determined from 5 May 2001 to 6 February 2002. Regions where birds concentrated from spring until returning to wintering areas included coastal waters from western Finnmark, Norway, to the eastern Taymyr Peninsula, Russia. Novaya Zemlya, Russia, particularly the Mollera Bay region, was used extensively during spring staging, moult, and autumn staging; regions of the Kola, Kanin, and Gydanskiy peninsulas, Russia, were used extensively during spring and moult migrations. Steller's eiders migrated across the Barents and Kara seas and along the Kara Sea and Kola Peninsula coastal waters to nesting, moulting, and wintering areas. The majority of marked eiders (9 of 15) were flightless in near‐shore waters along the west side of Novaya Zemlya. Eiders were also flightless in northern Norway and along the Kanin and at Kola Peninsula coasts. We compare and contrast natural history characteristics of the Atlantic and Pacific populations and discuss evolutionary and ecological factors influencing their distribution.     

Biosonar,dive, and foraging activity of satellite tracked harbor porpoises (Phocoena phocoena)

This study presents bioacoustic recordings in combination with movements and diving behavior of three free‐ranging harbor porpoises (a female and two males) in Danish waters. Each porpoise was equipped with an acoustic data logger (A‐tag), a time‐depth‐recorder, a VHF radio transmitter, and a satellite transmitter. The units were programmed to release after 24 or 72 h. Possible foraging occurred mostly near the surface or at the bottom of a dive. The porpoises showed individual diversity in biosonar activity (<100 to >50,000 clicks per hour) and in dive frequency (6–179 dives per hour). We confirm that wild harbor porpoises use more intense clicks than captive animals. A positive tendency between number of dives and clicks per hour was found for a subadult male, which stayed near shore. It showed a distinct day‐night cycle with low echolocation rates during the day, but five times higher rates and higher dive activity at night. A female traveling in open waters showed no diel rhythm, but its sonar activity was three times higher compared to the males'. Considerable individual differences in dive and echolocation activity could have been influenced by biological and physical factors, but also show behavioral adaptability necessary for survival in a complex coastal environment.