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Satellite Transmitters (satellite + transmitters)
Selected AbstractsForaging effort in relation to the constraints of reproduction in free-ranging albatrossesFUNCTIONAL ECOLOGY, Issue 1 2003S. A. Shaffer Summary 1Theoretical models predict that animals will vary their effort to maximize different currencies such as time and energy when the constraints of reproduction change during breeding, but this has been poorly studied in free-ranging animals. 2Foraging effort (energy per unit time) was examined by comparing mass changes, foraging costs and activity-specific behaviours of Wandering Albatrosses (Diomedea exulans Linnaeus) during the incubation and chick-brooding stages. In 1998, 38 albatrosses (20 during incubation and 18 during brooding) were injected with doubly labelled water and equipped with satellite transmitters and activity data loggers. 3During incubation, albatrosses travelled 3·7 times farther and were at sea 3·2 times longer, yet foraging costs were significantly lower than trips made during brooding (incubation 4·52 ± 0·50 SD W kg,1vs brooding 4·98 ± 0·55 SD W kg,1). 4The rate of daily mass gain decreased significantly with time at sea during incubation whereas the rate of daily mass gain increased significantly with time at sea during brooding. 5Foraging effort was higher during brooding, suggesting that birds were minimizing time at sea to maximize the rate of food delivery to chicks. In contrast, foraging effort was lower during incubation, suggesting that birds were maximizing time at sea and minimizing the energy costs of foraging. 6Foraging costs were also different between sexes. However, this was related to body size differences and not to differences in foraging effort as suggested in previous studies. [source] Protection of fixed service receivers from the interference produced by the non-geostationary satellites in a fixed satellite service network: a statistical interference analysisINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 1 2002José Mauro P. Fortes Abstract Until 1997, the power flux density (pfd) limits applicable to fixed satellite service (FSS) satellite transmitters to protect fixed service (FS) receivers operating in the same frequency band were those in Article 21 of the radio regulations. They were developed assuming that potentially interfering satellites in the FSS would only operate in the GSO. The need to revise these limits to allow for the protection of FS receivers from interference generated by non-geostationary satellites has led to several studies, most of them based on the non-realistic assumption that every visible satellite in a NGSO constellation produces the maximum allowed pfd level at the FS receive station location. To provide a quantitative indication of how pessimistic this assumption is, this paper considers a more realistic model in which the pfd entries reaching a given FS receiver location are characterized by statistically independent random variables. The probability density functions of these random variables depend on the operational characteristics of the NGSO network. The obtained results have also shown the need to consider some of the operational characteristics of NGSO satellite networks when evaluating the interference produced by their satellites. If these operational characteristics are not taken into account in the calculations, higher values of interference, that do not reflect the real interference environment, are obtained. Copyright © 2002 John Wiley & Sons, Ltd. [source] At-sea distribution and scale-dependent foraging behaviour of petrels and albatrosses: a comparative studyJOURNAL OF ANIMAL ECOLOGY, Issue 1 2007DAVID PINAUD Summary 1In order to study and predict population distribution, it is crucial to identify and understand factors affecting individual movement decisions at different scales. Movements of foraging animals should be adjusted to the hierarchical spatial distribution of resources in the environment and this scale-dependent response to environmental heterogeneity should differ according to the forager's characteristics and exploited habitats. 2Using First-Passage Time analysis, we studied scales of search effort and habitat used by individuals of seven sympatric Indian Ocean Procellariiform species fitted with satellite transmitters. We characterized their search effort distribution and examined whether species differ in scale-dependent adjustments of their movements according to the marine environment exploited. 3All species and almost all individuals (91% of 122 individuals) exhibited an Area-Restricted Search (ARS) during foraging. At a regional scale (1000s km), foraging ranges showed a large spatial overlap between species. At a smaller scale (100s km, at which an increase in search effort occurred), a segregation in environmental characteristics of ARS zones (where search effort is high) was found between species. 4Spatial scales at which individuals increased their search effort differed between species and also between exploited habitats, indicating a similar movement adjustment for predators foraging in the same habitat. ARS zones of the two populations of wandering albatross Diomedea exulans (Crozet and Kerguelen) were similar in their adjustments (i.e. same ARS scale) as well as in their environmental characteristics. These two populations showed a weak spatial overlap in their foraging distribution, with males foraging in more southerly waters than females in both populations. 5This study demonstrates that predators of several species adjust their foraging behaviour to the heterogeneous environment and these scale-dependent movement adjustments depend on both forager and environment characteristics. [source] Harlequin duck Histrionicus histrionicus population structure in eastern NearcticJOURNAL OF AVIAN BIOLOGY, Issue 2 2002Serge Brodeur During May 1996 and April 1997, eight harlequin duck males were captured and fitted with satellite transmitters while migrating along the shores of Forillon National Park, Québec, Canada. Another 17 males were equipped with satellite transmitters in river systems of eastern Hudson Bay, Ungava Bay and northern Labrador in June 1997 and 1998. Our objectives were to determine relationships between breeding, moulting and wintering areas, and to determine whether distinct population segments existed among harlequin ducks in eastern North America. All birds tracked from Forillon migrated to Labrador. Moulting areas were identified for six birds. Forillon males were followed to the eastern North American major wintering site in Maine. Males captured in northern Québec and Labrador migrated to moult and winter in south-western Greenland. Our data suggest the presence of two demographically distinct population segments in eastern North America, perhaps originating from the Pleistocene glacial refuge in western Greenland and south of the Laurentide ice sheet in eastern Canada or United States. [source] Seasonal foraging movements and migratory patterns of female Lamna ditropis tagged in Prince William Sound, AlaskaJOURNAL OF FISH BIOLOGY, Issue 2 2005L. B. Hulbert Conventional and electronic tags were used to investigate social segregation, distribution, movements and migrations of salmon sharks Lamna ditropis in Prince William Sound, Alaska. Sixteen salmon sharks were tagged with satellite transmitters and 246 with conventional tags following capture, and were then released in Prince William Sound during summer 1999 to 2001. Most salmon sharks sexed during the study were female (95%), suggesting a high degree of sexual segregation in the region. Salmon sharks congregated at adult Pacific salmon Oncorhynchus spp. migration routes and in bays near Pacific salmon spawning grounds in Prince William Sound during July and August. Adult Pacific salmon were the principal prey in 51 salmon shark stomachs collected during summer months in Prince William Sound, but the fish appeared to be opportunistic predators and consumed sablefish Anoplopoma fimbria, gadids, Pacific herring Clupea pallasi, rockfish Sebastes spp. and squid (Teuthoidea) even when adult Pacific salmon were locally abundant. As Pacific salmon migrations declined in late summer, the salmon sharks dispersed; some continued to forage in Prince William Sound and the Gulf of Alaska into autumn and winter months, while others rapidly moved south-east thousands of kilometres toward the west coasts of Canada and the U.S. Three movement modes are proposed to explain the movement patterns observed in the Gulf of Alaska and eastern North Pacific Ocean: ,focal foraging' movements, ,foraging dispersals' and ,direct migrations'. Patterns of salmon shark movement are possibly explained by spatio-temporal changes in prey quality and density, an energetic trade-off between prey availability and water temperature, intra-specific competition for food and reproductive success. Transmissions from the electronic tags also provided data on depth and water temperatures experienced by the salmon sharks. The fish ranged from the surface to a depth of 668 m, encountered water temperatures from 4·0 to 16·8° C and generally spent the most time above 40 m depth and between 6 and 14° C (60 and 73%, respectively). [source] HAUL-OUT ACTIVITY OF RINGED SEALS (PHOCA HISPIDA) DETERMINED FROM SATELLITE TELEMETRYMARINE MAMMAL SCIENCE, Issue 1 2002E. W. Born Abstract The haul-out activity of 15 ringed seals (Phoca hispida) equipped with satellite-linked radio transmitters was studied in NW Greenland (ca. 73°-78°N). Between 19 June 1997 and 30 June 1999, telemetry data on haulout activity were obtained by the "Land-Sea-Reporter" (LSR), "Time-at-Depth" (TAD), and "Timelines" (TIM) systems housed within the satellite transmitters. The haul-out activity (% of total time hauled out) reported by the TIM system, which is specifically designed for collecting haul-out data, was about 1.4 times higher than that inferred from the LSR, but only about 0.7 of that inferred from TAD data. The TIM were used to describe haul-out activity. A total of 1,011 d with TIM were obtained (64.5% of a total of 1,568 "seal-days" monitored) representing data from nearly an entire annual cycle. No differences were found in percentage of time hauled out per month among various age categories. At all seasons the haul-out time showed considerable individual variation. There were no trends in percentage of time hauled out per month during late summer, fall, and winter (August-February). During the High Arctic winter darkness (November-January) the percentage of haul-out per month ranged between 3.9% in an adult (SD = 2.44, range: 1.1%-5.7%, n= 3 mo) and 15.7% in a subadult (SD = 1.95, range: 13.7%-17.6%, n= 3 mo). From late March there was a significant increase in haul-out time. Between 1 and 30 June, when aerial surveys of basking ringed seals usually are conducted, the haul-out time (% per day) increased from about 25% to about 57%. No tendencies in diel haul-out activity were revealed. [source] Harbour seal movements and haul-out patterns: implications for monitoring and managementAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 4 2009Louise Cunningham Abstract 1.Compliance with conservation legislation requires knowledge on the behaviour, abundance and distribution of protected species. Seal life history is characterized by a combination of marine foraging and a requirement to haul out on a solid substrate for reproduction and moulting. Thus understanding the use of haul out sites, where seals are counted, as well as their at-sea movements is crucial for designing effective monitoring and management plans. 2.This study used satellite transmitters deployed on 24 harbour seals in western Scotland to examine movements and haul-out patterns. 3.The proportion of time harbour seals spent hauled out (daily means of between 11 and 27%) varied spatially, temporally and according to sex. The mean haul-out duration was 5,h, with a maximum of over 24,h. 4.Patterns of movement were observed at two geographical scales; while some seals travelled over 100,km, 50% of trips were within 25,km of a haul-out site. These patterns are important for the identification of a marine component to designated protected areas for the species. 5.On average seals returned to the haul-out sites they last used during 40% of trips, indicating a degree of site fidelity, though there was wide variation between different haul-out sites (range 0% to >75%). 6.Low fidelity haul-out sites could form a network of land-based protected areas, while high fidelity sites might form appropriate management units. Copyright © 2008 John Wiley & Sons, Ltd. [source] The initial journey of juvenile emperor penguinsAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue S1 2007Gerald L. Kooyman Abstract 1.The first major journey of emperor penguins, among several in their lifetime, is the juveniles' dispersal from their natal colony on a trip that takes them beyond Antarctic waters. The route taken by fledglings from Cape Washington (74.5°,S; 165.4°,E) was studied by applying satellite transmitters to ten individuals during December 1994,1996. In January 2001 transmitters with longer transmission capacity were also applied to six hand-fed fledglings, which had been held captive for one month while attaining a body mass exceeding that of wild birds. These post-captive birds were released at the ice edge of McMurdo Sound (77.5°,S; 165.0°,E), which is in the vicinity of other emperor penguin colonies, and 320,km south of their natal colony of Cape Washington. 2.Independent of their parents, the wild birds travelled north-east for the next two months, reaching locations as low as 57°,S. The post-captive birds travelled north also, but their trek reached only to about 63°,S before they turned south, or remained near their most northerly position from March through May. 3.It was concluded that among colonies in the southern Ross Sea: (a) most healthy fledglings survive at least the first two months at sea, feeding themselves as they go; (b) the Cape Washington fledglings travelled as far north as 57°,S, and much of this journey was in ice free waters; (c) by April, the post-captive birds reached at least as far as the large-scale pack ice edge and possibly beyond the edge at 63°,S; (d) by early March the trend north ends, and by about late March the birds travel to, or remain near the northern ice edge. 4.The reason the birds travel so far north remains a mystery. Copyright © 2008 John Wiley & Sons, Ltd. [source] | ||||||||||