Abstract
he migratory programme provides birds with the capacity to seasonally migrate thousands
of kilometres during their annual breeding cycle. This programme is governed by
endogenous, and environmentally-shaped, exogenous, processes. Using a diverse set of
tracking methods, this thesis investigates the two components of the migration programme to
understand, (1) how juvenile small-bodied birds migrate, (2) how the environment influences
migration in experienced birds, and (3) two long-term spatio-temporal patterns shaped by the
migration programme; latitudinal variation in migration strategy and genetic population
differentiation.
To shed light on the innate migration component, I studied the migration of a solitary
nocturnal long-distance migrant, the common cuckoo Cuculus canorus. Paper I investigates
the first migration of juvenile common cuckoos and compares it to that of adults. Juvenile
cuckoos, from northern European breeding grounds, migrated independently of adult
conspecifics using a different and straighter route, and were able to reach the populationspecific
winter grounds. In paper II I track the first migration of experimentally displaced
juvenile cuckoos to investigate whether the navigation ability is inherited. Displaced birds did
not show evidence of displacement compensation since migration directions were similar in
both displaced and non-displaced juveniles. Taken together, the innate mechanism of
migration in cuckoos can facilitate the migration to specific winter grounds (vectororientation)
and possibly includes a simple navigation capability that enables juveniles to
compensate for crosswind en route, but not to compensate for experimental displacement.
To study exogenous influence, paper III and IV investigate how environmental factors shape
movements of migratory birds at local and global scale, with a focus on food resource
availability. Paper III investigates the relation between migration schedules and vegetation
greenness (surrogate of food resources) during the full annual cycle in three long-distance
insectivore migrants, common cuckoos, red-backed shrikes Lanius collurio and thrush
nightingales Luscinia luscinia. It also looks at how the migration routes can be affected by
future climate change. Results indicate that insectivore long-distance migrants temporally
adjust migration schedules with seasonal surplus of vegetation greenness during the annual
cycle. Climate projections suggest that migration routes may be affected by climate change,
especially before or after crossing the Sahara Desert. Paper IV links the global-scale
resource-tracking pattern found in paper III to local movements of thrush nightingales during
breeding. Results of paper IV suggest that vegetation greenness influence the movement at
local scale as well, but chick rearing, temperature and rain are also important factors.
Paper V and VI investigate latitudinal variation in migration strategy and genetic population
differentiation as long-term patterns partially shaped by the migration programme. Paper V
aims to understand the migration strategy of three Iberian breeding migrants, white-rumped
swifts Apus caffer, rufous scrub-robins Erythropygia galactotes and azuricollis bluethroats
Luscinia svecica, compared to a range of northern breeding birds. Iberian migrants spent
longer time than northern migrants in autumn migration, but in spring migration their speed
was more similar to northern migrants. Results indicate that Iberian migrants are less time
constrained than northern migrants, but only in autumn, and this may be related to their
shorter migration distance. In paper VI, I take a retrospective perspective on the population
differentiation process that shapes population structure in red-backed shrikes. Red-backed
shrikes from northern Europe and Spain share a detoured route in spring migration from the
winter grounds to the eastern Mediterranean region, but details on the routes from the eastern
part of the breeding range in Siberia are still lacking. Using genomic analysis, I investigate
the structure of distant populations, as a first step to infer the colonization history of the
species across the breeding range and the origin of such detoured migration route. Overall,
the results presented here contribute to the understanding of the innate migration programme
and the external factors that influence the programme at local and global scales and how
of kilometres during their annual breeding cycle. This programme is governed by
endogenous, and environmentally-shaped, exogenous, processes. Using a diverse set of
tracking methods, this thesis investigates the two components of the migration programme to
understand, (1) how juvenile small-bodied birds migrate, (2) how the environment influences
migration in experienced birds, and (3) two long-term spatio-temporal patterns shaped by the
migration programme; latitudinal variation in migration strategy and genetic population
differentiation.
To shed light on the innate migration component, I studied the migration of a solitary
nocturnal long-distance migrant, the common cuckoo Cuculus canorus. Paper I investigates
the first migration of juvenile common cuckoos and compares it to that of adults. Juvenile
cuckoos, from northern European breeding grounds, migrated independently of adult
conspecifics using a different and straighter route, and were able to reach the populationspecific
winter grounds. In paper II I track the first migration of experimentally displaced
juvenile cuckoos to investigate whether the navigation ability is inherited. Displaced birds did
not show evidence of displacement compensation since migration directions were similar in
both displaced and non-displaced juveniles. Taken together, the innate mechanism of
migration in cuckoos can facilitate the migration to specific winter grounds (vectororientation)
and possibly includes a simple navigation capability that enables juveniles to
compensate for crosswind en route, but not to compensate for experimental displacement.
To study exogenous influence, paper III and IV investigate how environmental factors shape
movements of migratory birds at local and global scale, with a focus on food resource
availability. Paper III investigates the relation between migration schedules and vegetation
greenness (surrogate of food resources) during the full annual cycle in three long-distance
insectivore migrants, common cuckoos, red-backed shrikes Lanius collurio and thrush
nightingales Luscinia luscinia. It also looks at how the migration routes can be affected by
future climate change. Results indicate that insectivore long-distance migrants temporally
adjust migration schedules with seasonal surplus of vegetation greenness during the annual
cycle. Climate projections suggest that migration routes may be affected by climate change,
especially before or after crossing the Sahara Desert. Paper IV links the global-scale
resource-tracking pattern found in paper III to local movements of thrush nightingales during
breeding. Results of paper IV suggest that vegetation greenness influence the movement at
local scale as well, but chick rearing, temperature and rain are also important factors.
Paper V and VI investigate latitudinal variation in migration strategy and genetic population
differentiation as long-term patterns partially shaped by the migration programme. Paper V
aims to understand the migration strategy of three Iberian breeding migrants, white-rumped
swifts Apus caffer, rufous scrub-robins Erythropygia galactotes and azuricollis bluethroats
Luscinia svecica, compared to a range of northern breeding birds. Iberian migrants spent
longer time than northern migrants in autumn migration, but in spring migration their speed
was more similar to northern migrants. Results indicate that Iberian migrants are less time
constrained than northern migrants, but only in autumn, and this may be related to their
shorter migration distance. In paper VI, I take a retrospective perspective on the population
differentiation process that shapes population structure in red-backed shrikes. Red-backed
shrikes from northern Europe and Spain share a detoured route in spring migration from the
winter grounds to the eastern Mediterranean region, but details on the routes from the eastern
part of the breeding range in Siberia are still lacking. Using genomic analysis, I investigate
the structure of distant populations, as a first step to infer the colonization history of the
species across the breeding range and the origin of such detoured migration route. Overall,
the results presented here contribute to the understanding of the innate migration programme
and the external factors that influence the programme at local and global scales and how
| Originalsprog | Engelsk |
|---|
| Forlag | Natural History Museum of Denmark, Faculty of Science, University of Copenhagen |
|---|---|
| Status | Udgivet - 2017 |