Tracking migratory movements of birds between breeding and wintering areas is important for both theoretical and conservation purposes. In particular, information about linkages between stages of the annual cycle (i.e., migratory connectivity) is essential for identifying factors and processes limiting population sizes of birds. Further, this information is necessary for testing assumptions and hypotheses about the evolution of avian migratory patterns. Here, I used stable hydrogen isotope (δD) analyses of tissues representing different periods and geographic regions of the annual cycle of white-throated sparrows, Zonotrichia albicollis, to provide new information on spatial and temporal linkages between stages of the annual cycle of this species. To achieve this objective, I sampled white-throated sparrows during spring and fall migration of 2002 and 2003 at a key staging ground for North American migratory birds located at Delta Marsh, Manitoba. Based on evaluations of the correspondence between δD values of feathers, claws, and cellular portions of blood of migrants, I determined that δD values of claws and blood cells were not suitable for estimating wintering origins of individuals captured en route to breeding areas. However, δD values of head feathers grown on wintering areas and tail feathers grown on breeding areas corresponded to values expected for feathers grown in broad areas within the wintering and breeding range of the species, respectively. The δD values of feathers showed no relationship between estimated breeding or natal and wintering latitudes of white-throated sparrows. However, band-encounter analyses indicated a clear eastwest segregation of populations across Canada, a finding that suggests that this species has a parallel migration system. Temporally, all components of the breeding populations migrated together during spring migration. However, as expected, white-throated sparrows exhibited sex-biased differential timing of spring arrival and latitude of wintering origin. Consistent with several other differential migrants, female white-throated sparrows arrived later and originated from more southern latitudes. There was also a negative relationship between wintering latitude and arrival dates of individuals during the second spring of the study. The existence of this relationship is a key assumption of differential migration hypotheses that had not been previously validated. Furthermore, since timing of arrival at breeding areas is critical to establishing high-quality territories and pair bonds, relationships between wintering latitude and arrival date of individuals could have important carry-over effects to reproduction. Based on standard body condition indices, white-throated sparrows migrating longer distances to reach breeding areas were not in poorer body condition than those migrating shorter distances. Thus, the cost of migrating longer distances does not appear to affect pre-breeding body condition, a parameter known to be linked with reproductive success.

Tracking migratory movements of birds between breeding and wintering areas is important for both theoretical and conservation purposes. In particular, information about linkages between stages of the annual cycle (i.e., migratory connectivity) is essential for identifying factors and processes limiting population sizes of birds. Further, this information is necessary for testing assumptions and hypotheses about the evolution of avian migratory patterns. Here, I used stable hydrogen isotope (δD) analyses of tissues representing different periods and geographic regions of the annual cycle of white-throated sparrows, Zonotrichia albicollis, to provide new information on spatial and temporal linkages between stages of the annual cycle of this species. To achieve this objective, I sampled white-throated sparrows during spring and fall migration of 2002 and 2003 at a key staging ground for North American migratory birds located at Delta Marsh, Manitoba. Based on evaluations of the correspondence between δD values of feathers, claws, and cellular portions of blood of migrants, I determined that δD values of claws and blood cells were not suitable for estimating wintering origins of individuals captured en route to breeding areas. However, δD values of head feathers grown on wintering areas and tail feathers grown on breeding areas corresponded to values expected for feathers grown in broad areas within the wintering and breeding range of the species, respectively. The δD values of feathers showed no relationship between estimated breeding or natal and wintering latitudes of white-throated sparrows. However, band-encounter analyses indicated a clear eastwest segregation of populations across Canada, a finding that suggests that this species has a parallel migration system. Temporally, all components of the breeding populations migrated together during spring migration. However, as expected, white-throated sparrows exhibited sex-biased differential timing of spring arrival and latitude of wintering origin. Consistent with several other differential migrants, female white-throated sparrows arrived later and originated from more southern latitudes. There was also a negative relationship between wintering latitude and arrival dates of individuals during the second spring of the study. The existence of this relationship is a key assumption of differential migration hypotheses that had not been previously validated. Furthermore, since timing of arrival at breeding areas is critical to establishing high-quality territories and pair bonds, relationships between wintering latitude and arrival date of individuals could have important carry-over effects to reproduction. Based on standard body condition indices, white-throated sparrows migrating longer distances to reach breeding areas were not in poorer body condition than those migrating shorter distances. Thus, the cost of migrating longer distances does not appear to affect pre-breeding body condition, a parameter known to be linked with reproductive success.

Improving our understanding of the factors that shape the demography of populations now requires that we consider no event in isolation, and instead express current performance as a product of previous events and processes. Patterns of site choice and dispersal likely underpin a large proportion of the variation in reproductive success among individuals, but the consequences of dispersal decisions may only become apparent many months later at a separate stage of the annual cycle Only by studying the interactions among seasons can we determine how differences in annual routine translate into asymmetries in fitness, and subsequently apply this understanding to processes occurring at the population level. This thesis begins with a review of the phenomena known as carry-over effects (COEs; Chapter 2), where I find evidence to support their occurrence in a multitude of taxa and identify previously unconsidered drivers of carry-over effects that could potentially explain their widespread nature. The remainder of this thesis comprises empirical work using light-bellied Brent geese (Branta bernicla hrota) as a model system to study these processes. In Chapter 3 I show evidence of a COE in Brent geese mediated by body condition, but in addition demonstrate how the strength of this effect is moderated by downstream climatic conditions operating in a density-independent fashion. Chapter 4 describes the development of novel polymorphic microsatellite loci to be used in population genetic and parentage studies. In Chapter 5 I show that light-bellied Brent geese are highly site faithful and that this fidelity has a cultural basis. Finally in Chapter 6 I characterize patterns of mate choice, and investigate potential consequences of this pattern in light of the observed site fidelity, in terms of risk of inbreeding. Collectively my results demonstrate the utility of combining long-term datasets with genetic pedigrees to investigate patterns of dispersal in a migratory species. Moreover they highlight the necessity to study individual performance in the context of the entire annual cycle in order to fully characterize the nature and strength of fitness determinants operating at multiple stages in a migratory species.

Movements of long-distance migratory birds are frequently well timed and routed in order to maximise individual fitness. However, individual timing of events or environmental conditions experienced have a potential to carry over into subsequent annual cycle stages and may have delayed fitness consequences. Therefore, knowledge of these seasonal interactions is crucial to identify key periods and regions that limit survival beyond the breeding period and thus to fully understand population dynamics of migratory species. Despite current evidence for seasonal interactions, there is no detailed knowledge of the complex of relationships within the full annual cycle, differences between sexes and populations or impact of environmental conditions during moult in one species. To unveil this system of seasonal interactions within the annual cycle, we directly tracked 103 great reed warblers (Acrocephalus arundinaceus) using light-level geolocators from five breeding sites across the breeding range to obtain information on timing and positions of annual cycle events. We then combined this information with various remotely sensed habitat condition metrics and stable isotopic composition of feathers from the non-breeding grounds to identify and quantify carry-over effects within the full annual cycle. Our...