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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 274 (1978), S. 154-156 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The experiments were conducted near Clemson, South Carolina during the spring and autumn of 1977. Individuals mist-netted during the winter in the Clemson area were used in spring orientation tests, and experiments carried out in the autumn involved birds netted in North Dakota at the onset of ...
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of ornithology 135 (1994), S. 393-397 
    ISSN: 1439-0361
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Behavioral ecology and sociobiology 39 (1996), S. 1-10 
    ISSN: 1432-0762
    Keywords: Key words Bird migration ; Migratory orientation ; Ecological context ; Fat stores ; Cue integration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract How and when migrants integrate directional information from different sources may depend not only on the bird’s internal state, including fat stores, but also on the ecological context during passage. We designed experiments to (1) examine the influence of stored fat on the decision to migrate and on the choice of migratory direction and (2) investigate how the integration of orientation cue information is tied to energetic status in relation to migration across an ecological barrier. Migratory orientation of red-eyed vireos (Vireo olivaceus) at twilight was recorded using two different techniques, orientation cage experiments and free-flight release tests, during both fall and spring migration. During fall migration, the amount of stored fat proved decisive for directional selections of the vireos. Fat birds chose directions in accordance with migration across the Gulf of Mexico. Lean birds oriented either parallel to the coast line (cage tests) or moved inland (free-flight releases). Whereas only fat birds showed significant responses to experimental deflections of the geomagnetic field, lean birds displayed a tendency to shift their activity in the expected direction, making it difficult to evaluate the prediction that use of the magnetic compass is context dependent. Fat loads also had a significant effect on the decision to migrate, i.e., fat individuals were more likely to embark on migration than were lean birds (true for both cage and release experiments). During spring migration, a majority of experimental subjects were classified as lean, following their arrival after crossing the Gulf of Mexico, and oriented in seasonally appropriate directions. The vireos also showed significant responses to experimental deflections of the geomagnetic field regardless of their energetic status. Free-flight release experiments during spring migration revealed a significant difference in mean directions between clear sky and overcast tests. The difference may indicate a compensatory response to wind drift or possibly a need for celestial cues to calibrate the magnetic compass. Finally, this is the first demonstration of magnetic compass orientation in a North American vireo.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Behavioral ecology and sociobiology 28 (1991), S. 85-90 
    ISSN: 1432-0762
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Local concentrations of migrating, fat-depleted birds with similar diets can lead to increased competition for food at a time when energy demand is high. Results of a predator-exclosure experiment indicate that intercontinental passerine migrants depress food abundance during stopover following migration across the Gulf of Mexico. Moreover, migrants that stop when a high number of potential competitors are present replenish energy reserves more slowly than migrants that stop under low density conditions. Competition increase the rate of food depletion and may decrease the probability that a migrant will meet its energetic requirements and complete a successful migration.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Behavioral ecology and sociobiology 31 (1992), S. 189-193 
    ISSN: 1432-0762
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Migrating birds derive compass information from the sun, stars, geomagnetic field and polarized light, but relatively little is known about how these multiple sources of directional information are integrated into a functional orientation system. We found that migratory warblers exposed to a rotated polarized light pattern at sunset oriented at a constant angle to the axis of polarization. When polarized light cues were eliminated, this shifted orientation was maintained relative to the setting sun. Polarized light patterns, thus, appear to provide a calibration reference for the sun compass in nocturnal migrants, and may also play a role in calibrating other compass systems.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Behavioral ecology and sociobiology 3 (1978), S. 173-176 
    ISSN: 1432-0762
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. Interspecific aggression is viewed as a device of behavioral interference employed in resource competition with individuals of other species. Aggression-mediated competition is costly in terms of time and energy invested as well as increased risk of injury or predation. Consequently, natural selection should favor recognition of competitors and differential aggression depending upon the degree of competitive overlap. 2. Mockingbirds (Mimus polyglottos) inhabiting a residential area in the piedmont region of South Carolina (USA) maintain winter feeding territories within which they defend fruit-laden trees and shrubs. Several of the many species occurring with the mockingbird in the study area are frugivorous and represent to varying degrees resource competitors, thus offering an opportunity to study interspecific aggression. 3. Field observations of mockingbird interactions with members of other species reveal that frugivores provoke mockingbird aggression while non-frugivores are essentially ignored. Moreover, the aggressiveness is directly proportional to the extent of frugivory among competitors.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Behavioral ecology and sociobiology 10 (1982), S. 153-155 
    ISSN: 1432-0762
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary If savannah sparrows, (Passerculus sandwichensis), a North American night migrant, select a migratory heading based upon the setting sun, a shift in the position of that cue should produce a predictable shift in the migrant's nocturnal orientation. I tested this hypothesis by shifting the sunst position with mirrors and by recording the bird's orientation in Emlen funnels. The control group displayed directionality appropriate for spring migration (ā=342°). The mean heading of experimentals (ā=272°), which were exposed to a cue-shifted situation, was in the expected westerly direction relative to the control mean (P〈0.05, V-test). The setting sun appears to be a sufficient source of directional information for this avian migrant.
    Type of Medium: Electronic Resource
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  • 8
    Publication Date: 2015-11-02
    Description: Approximately two thirds of migratory songbirds in eastern North America negotiate the Gulf of Mexico (GOM), where inclement weather coupled with no refueling or resting opportunities can be lethal. However, decisions made when navigating such features and their consequences remain largely unknown due to technological limitations of tracking small animals over large areas. We used automated radio telemetry to track three songbird species (Red-eyed Vireo, Swainson’s Thrush, Wood Thrush) from coastal Alabama to the northern Yucatan Peninsula (YP) during fall migration. Detecting songbirds after crossing ∼1,000 km of open water allowed us to examine intrinsic (age, wing length, fat) and extrinsic (weather, date) variables shaping departure decisions, arrival at the YP, and crossing times. Large fat reserves and low humidity, indicative of beneficial synoptic weather patterns, favored southward departure across the Gulf. Individuals detected in the YP departed with large fat reserves and later in the fall with profitable winds, and flight durations (mean = 22.4 h) were positively related to wind profit. Age was not related to departure behavior, arrival, or travel time. However, vireos negotiated the GOM differently than thrushes, including different departure decisions, lower probability of detection in the YP, and longer crossing times. Defense of winter territories by thrushes but not vireos and species-specific foraging habits may explain the divergent migratory behaviors. Fat reserves appear extremely important to departure decisions and arrival in the YP. As habitat along the GOM is degraded, birds may be limited in their ability to acquire fat to cross the Gulf.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 9
    Publication Date: 2014-01-01
    Description: The behavior of long-distance migrants during stopover is constrained by the need to quickly and safely replenish energetic reserves. Replenishing fuel stores at stopover sites requires adjusting to unfamiliar landscapes with little to no information about the distribution of resources. Despite their critical importance to the success of songbird migration, the effects of landscape composition and configuration on fuel deposition rates (FDR [g/d]), the currency of migration, has not been tested empirically. Our objectives were to understand the effects of heterogeneous landscapes on FDR of forest-dwelling songbirds during spring migration. The results of field experiments were used to parameterize a spatially explicit, individual-based model of forest songbird movement and resulting FDR. Further field experiments were used to validate the results from the individual-based model. In simulation experiments, we altered a Gulf South landscape in a factorial design to predict the effects of future patterns under different scenarios of land use change in which the abundance of high-quality hardwood habitat and the spatial aggregation of habitat varied. Simulated FDR decreased as the amount of hardwood in the landscape decreased from 41% to 22% to 12%. Further, migrants that arrived in higher-quality habitat types gained more mass. Counter to our expectations, FDR was higher with lower spatial aggregation of habitat. Differences in refueling rates may be most influenced by whether or not an individual experiences an initial searching cost after landing in poor-quality habitat. Therefore, quickly locating habitat with sufficient food resources at each stopover may be the most important factor determining a successful migration. Our findings provide empirical evidence for the argument that hardwood forest cover is a primary determinant of the quality of a stopover site in this region. This study represents the first effort to empirically quantify FDRs based on the configuration of landscapes. # doi:10.1890/12-1867.1
    Print ISSN: 1051-0761
    Electronic ISSN: 1939-5582
    Topics: Biology
    Published by Wiley on behalf of The Ecological Society of America (ESA).
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