Abstract
Migratory movements of birds has always fascinated man and led to many questions
concerning the ecological drivers behind, the necessary adaptations and the navigational abilities required. However, especially for the long-distance migrants, basic descriptions of their movements are still lacking and many experiments are only becoming possible with the current development of tracking technologies.
During this thesis work I have been tracking the poorly known movements of several
species of long-distance migrants and document highly complex migration patterns.
In three manuscripts these movements were related to the yearly progression of an
environmental surrogate for food availability along the course of migration. In one species, with multiple, different non-breeding staging sites, environmental conditions explain movements well and also how yearly differences explain differences in timing. In another species, environmental conditions are not a good predictor of movements, and possibly effects of timing constraints or food type play a role.
Two manuscripts focus on the effects of human-induced habitat alterations on
migratory behaviour. One compares the movements of partial migrants in urban
habitats with those in rural habitats. Some species have decreased the frequency of
migrants and migration distance in urban environments, and others have not. The other manuscript describes the small scale movements of three different Palaearctic
migrants during winter in Africa in a farmland habitat and a forest reserve. In the degraded habitat all species used more space, although the consequence on bird density is less clear.
Two manuscripts relate the migratory movements of a long-distance migrant with
models of navigation. One compares model predictions obtained by simulation with actual movements, and conclude that the currently believed theoretical framework is insufficient to explain the observed performance. The other study investigates the ability of a displaced experienced migrant to navigate back to the normal migration route. It documents the capability, but also finds interesting patterns in when and where the bird compensated for the displacement. The last paper investigates effects of habitat shading on the performance of light-level based geolocation and compares experimental data with data from real tracking studies. This illustrates some of the potential problems and limitations of geolocation by light.
concerning the ecological drivers behind, the necessary adaptations and the navigational abilities required. However, especially for the long-distance migrants, basic descriptions of their movements are still lacking and many experiments are only becoming possible with the current development of tracking technologies.
During this thesis work I have been tracking the poorly known movements of several
species of long-distance migrants and document highly complex migration patterns.
In three manuscripts these movements were related to the yearly progression of an
environmental surrogate for food availability along the course of migration. In one species, with multiple, different non-breeding staging sites, environmental conditions explain movements well and also how yearly differences explain differences in timing. In another species, environmental conditions are not a good predictor of movements, and possibly effects of timing constraints or food type play a role.
Two manuscripts focus on the effects of human-induced habitat alterations on
migratory behaviour. One compares the movements of partial migrants in urban
habitats with those in rural habitats. Some species have decreased the frequency of
migrants and migration distance in urban environments, and others have not. The other manuscript describes the small scale movements of three different Palaearctic
migrants during winter in Africa in a farmland habitat and a forest reserve. In the degraded habitat all species used more space, although the consequence on bird density is less clear.
Two manuscripts relate the migratory movements of a long-distance migrant with
models of navigation. One compares model predictions obtained by simulation with actual movements, and conclude that the currently believed theoretical framework is insufficient to explain the observed performance. The other study investigates the ability of a displaced experienced migrant to navigate back to the normal migration route. It documents the capability, but also finds interesting patterns in when and where the bird compensated for the displacement. The last paper investigates effects of habitat shading on the performance of light-level based geolocation and compares experimental data with data from real tracking studies. This illustrates some of the potential problems and limitations of geolocation by light.
| Originalsprog | Engelsk |
|---|---|
| Udgiver | |
| Status | Udgivet - 2013 |