Sökning: "reverse migration"

Visar resultat 1 - 5 av 23 avhandlingar innehållade orden reverse migration.

1. 1. Flight Behaviour of Passerines on Nocturnal Migration

   Författare :Cecilia Nilsson; Evolutionär ekologi; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Bird migration; Passerines; Flight Behaviour; Tracking radar; Optimal migration; Flight speed; Airspeed; Wind drift; Nocturnal migration; Coastline effects; Flight directions; Reverse migration;

   Sammanfattning : Many passerines migrate during the night and at high altitudes, making their migration difficult to observe. By using tracking radars we have been able to make exact observations of the flight behaviour of passerines on nocturnal migration, which has enabled us to test several hypotheses about adaptive values and constraints regarding migratory behaviour in different ecological contexts. LÄS MER

3. 2. Economics of Migration

   Författare :Peter Karpestam; Nationalekonomiska institutionen; []
   Nyckelord :SAMHÄLLSVETENSKAP; SOCIAL SCIENCES; Time; Simulations; Remittances; Panel Data; Multiplier Effects; Migration; The Labor Market; Education; Informal and Formal Sectors;

   Sammanfattning : Abstract Population movements are more substantial today than at any other point in human history. If managed effectively, migration can be beneficial for all aspects of social and economic life. This thesis contains four papers, all of which are related to the economic consequences and determinants of migration, within and across countries. LÄS MER

4. 3. Individual consistency in bird migration

   Författare :YANNIS VARDANIS; Evolutionär ekologi; []
   Nyckelord :bird migration; telemetry; bird ringing; individual consistency; repeatability; site fidelity; routes; timing; annual cycle; meta-analysis;

   Sammanfattning : Slight differences, which appear in the individual animals of the same species and population have been recognised and appreciated ever since Darwin. These consistent intra-specific differences in animals have been considered very important because they are often inherited, and thus, provide the basic material for evolution to act on. LÄS MER

5. 4. Stopover behaviour in migratory songbirds: timing, orientation and departures

   Författare :Sissel Sjöberg; Funktionell zoologi; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; flight duration; orientation; departure timing; stopover behaviour; stopover duration; flight behaviour; reverse migration; route choice; compass calibration; passerines; Bird migration;

   Sammanfattning : Songbird migrants use stopovers between flight bouts to rest and refuel for the upcoming flights. Behaviours affecting where, when and how long to stay at stopover sites will affect how successful the overall migration will be, which has significant consequences for the overall fitness and mortality of the birds. LÄS MER

7. 5. Bird orientation: external cues and ecological factors

   Författare :Johan Bäckman; Evolutionär ekologi; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; tracking radar; Emlen funnel.; Animal ecology; Djurekologi; oscillatory orientation; roosting flight; scatter; concentration; heading; cue calibration; light dependent; magnetoreception; subcutaneous fat stores; body condition; energetics; geomagnetic field; visual cues; orientation; birds; migration;

   Sammanfattning : Birds are generally capable of accurate orientation. In this thesis I present studies about the external cues and the ecological factors that influences bird orientation. A multitude of environmental cues are used to select and maintain a proper direction. LÄS MER