Internal and external factors shaping movement and distributions of trans-Saharan migrants

TY - BOOK

T1 - Internal and external factors shaping movement and distributions of trans-Saharan migrants

AU - Vega, Marta Lomas

PY - 2017

Y1 - 2017

N2 - he migratory programme provides birds with the capacity to seasonally migrate thousandsof kilometres during their annual breeding cycle. This programme is governed byendogenous, and environmentally-shaped, exogenous, processes. Using a diverse set oftracking methods, this thesis investigates the two components of the migration programme tounderstand, (1) how juvenile small-bodied birds migrate, (2) how the environment influencesmigration in experienced birds, and (3) two long-term spatio-temporal patterns shaped by themigration programme; latitudinal variation in migration strategy and genetic populationdifferentiation.To shed light on the innate migration component, I studied the migration of a solitarynocturnal long-distance migrant, the common cuckoo Cuculus canorus. Paper I investigatesthe first migration of juvenile common cuckoos and compares it to that of adults. Juvenilecuckoos, from northern European breeding grounds, migrated independently of adultconspecifics using a different and straighter route, and were able to reach the populationspecificwinter grounds. In paper II I track the first migration of experimentally displacedjuvenile cuckoos to investigate whether the navigation ability is inherited. Displaced birds didnot show evidence of displacement compensation since migration directions were similar inboth displaced and non-displaced juveniles. Taken together, the innate mechanism ofmigration in cuckoos can facilitate the migration to specific winter grounds (vectororientation)and possibly includes a simple navigation capability that enables juveniles tocompensate for crosswind en route, but not to compensate for experimental displacement.To study exogenous influence, paper III and IV investigate how environmental factors shapemovements of migratory birds at local and global scale, with a focus on food resourceavailability. Paper III investigates the relation between migration schedules and vegetationgreenness (surrogate of food resources) during the full annual cycle in three long-distanceinsectivore migrants, common cuckoos, red-backed shrikes Lanius collurio and thrushnightingales Luscinia luscinia. It also looks at how the migration routes can be affected byfuture climate change. Results indicate that insectivore long-distance migrants temporallyadjust migration schedules with seasonal surplus of vegetation greenness during the annualcycle. 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-scaleresource-tracking pattern found in paper III to local movements of thrush nightingales duringbreeding. Results of paper IV suggest that vegetation greenness influence the movement atlocal 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 populationdifferentiation as long-term patterns partially shaped by the migration programme. Paper Vaims to understand the migration strategy of three Iberian breeding migrants, white-rumpedswifts Apus caffer, rufous scrub-robins Erythropygia galactotes and azuricollis bluethroatsLuscinia svecica, compared to a range of northern breeding birds. Iberian migrants spentlonger time than northern migrants in autumn migration, but in spring migration their speedwas more similar to northern migrants. Results indicate that Iberian migrants are less timeconstrained than northern migrants, but only in autumn, and this may be related to theirshorter migration distance. In paper VI, I take a retrospective perspective on the populationdifferentiation process that shapes population structure in red-backed shrikes. Red-backedshrikes from northern Europe and Spain share a detoured route in spring migration from thewinter grounds to the eastern Mediterranean region, but details on the routes from the easternpart of the breeding range in Siberia are still lacking. Using genomic analysis, I investigatethe structure of distant populations, as a first step to infer the colonization history of thespecies 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 programmeand the external factors that influence the programme at local and global scales and how

AB - he migratory programme provides birds with the capacity to seasonally migrate thousandsof kilometres during their annual breeding cycle. This programme is governed byendogenous, and environmentally-shaped, exogenous, processes. Using a diverse set oftracking methods, this thesis investigates the two components of the migration programme tounderstand, (1) how juvenile small-bodied birds migrate, (2) how the environment influencesmigration in experienced birds, and (3) two long-term spatio-temporal patterns shaped by themigration programme; latitudinal variation in migration strategy and genetic populationdifferentiation.To shed light on the innate migration component, I studied the migration of a solitarynocturnal long-distance migrant, the common cuckoo Cuculus canorus. Paper I investigatesthe first migration of juvenile common cuckoos and compares it to that of adults. Juvenilecuckoos, from northern European breeding grounds, migrated independently of adultconspecifics using a different and straighter route, and were able to reach the populationspecificwinter grounds. In paper II I track the first migration of experimentally displacedjuvenile cuckoos to investigate whether the navigation ability is inherited. Displaced birds didnot show evidence of displacement compensation since migration directions were similar inboth displaced and non-displaced juveniles. Taken together, the innate mechanism ofmigration in cuckoos can facilitate the migration to specific winter grounds (vectororientation)and possibly includes a simple navigation capability that enables juveniles tocompensate for crosswind en route, but not to compensate for experimental displacement.To study exogenous influence, paper III and IV investigate how environmental factors shapemovements of migratory birds at local and global scale, with a focus on food resourceavailability. Paper III investigates the relation between migration schedules and vegetationgreenness (surrogate of food resources) during the full annual cycle in three long-distanceinsectivore migrants, common cuckoos, red-backed shrikes Lanius collurio and thrushnightingales Luscinia luscinia. It also looks at how the migration routes can be affected byfuture climate change. Results indicate that insectivore long-distance migrants temporallyadjust migration schedules with seasonal surplus of vegetation greenness during the annualcycle. 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-scaleresource-tracking pattern found in paper III to local movements of thrush nightingales duringbreeding. Results of paper IV suggest that vegetation greenness influence the movement atlocal 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 populationdifferentiation as long-term patterns partially shaped by the migration programme. Paper Vaims to understand the migration strategy of three Iberian breeding migrants, white-rumpedswifts Apus caffer, rufous scrub-robins Erythropygia galactotes and azuricollis bluethroatsLuscinia svecica, compared to a range of northern breeding birds. Iberian migrants spentlonger time than northern migrants in autumn migration, but in spring migration their speedwas more similar to northern migrants. Results indicate that Iberian migrants are less timeconstrained than northern migrants, but only in autumn, and this may be related to theirshorter migration distance. In paper VI, I take a retrospective perspective on the populationdifferentiation process that shapes population structure in red-backed shrikes. Red-backedshrikes from northern Europe and Spain share a detoured route in spring migration from thewinter grounds to the eastern Mediterranean region, but details on the routes from the easternpart of the breeding range in Siberia are still lacking. Using genomic analysis, I investigatethe structure of distant populations, as a first step to infer the colonization history of thespecies 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 programmeand the external factors that influence the programme at local and global scales and how

UR - https://rex.kb.dk/primo-explore/fulldisplay?docid=KGL01010655736&context=L&vid=NUI&search_scope=KGL&isFrbr=true&tab=default_tab&lang=da_DK

M3 - Ph.D. thesis

BT - Internal and external factors shaping movement and distributions of trans-Saharan migrants

PB - Natural History Museum of Denmark, Faculty of Science, University of Copenhagen

ER -