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From Routes, non-breeding Sites and Timing to Reproductive Success - Migration Patterns in Hoopoes and Wrynecks


van Wijk, Rinus Ewout. From Routes, non-breeding Sites and Timing to Reproductive Success - Migration Patterns in Hoopoes and Wrynecks. 2016, University of Zurich, Faculty of Science.

Abstract

SUMMARY The annual cycle of migrating birds encompasses many perils and obstacles, but it allows birds to avoid food scarcity during winters, which is common when breeding grounds are influenced by a temperate climate. Migration is thus beneficial for survival, but it may also incur fitness costs. For example, it can influence current reproductive success. To better understand the population dynamics of migrants and for their proper conservation, it is crucial to study their complete annual cycle: migration routes, timing, non-breeding sites, but also potential consequences on reproductive success. In this thesis, I studied these aspects in Hoopoes Upupa epops and Wrynecks Jynx torquilla using geolocators that were deployed between 2010-2015 on individuals of breeding populations in Southern Switzerland (Valais) and likewise used data on breeding phenology for the same time span. In order to investigate the migratory behaviour of individual birds, devices have to be used to keep track of their whereabouts. Non-invasive techniques exist, such as stable isotopes, but these techniques only give relatively poor and coarse information on the whereabouts of an individual. The use of e.g. geolocators can give more precise information, but may lead to a change in behaviour and thus also might affect migration patterns. I show in chapter 2 using an extensive set of investigated parameters, ranging from fledgling weight to apparent annual survival, that Hoopoes were not affected by carrying a geolocator with a weight corresponding to <2% of their body mass. I conclude that with the proper design and an as low as possible relative weight of a device, they can be used and give invaluable insights into detailed migratory behaviour of an individual. One aspect that is key to the understanding of population dynamics, also in the light of conservation, is where birds spend the wintering (non-breeding) season. Contrary to previous believes I show that Wrynecks from Central-European populations are short-distance migrants wintering in Northern Africa and on the Iberian Peninsula (chapter 3). Similar to their breeding grounds they prefer agricultural habitat with shrubs/orchards and patches of open, sandy soil where they can forage on ants, their main food source (chapter 4). Both findings have implications for understanding the mechanisms behind population dynamics of not only Wrynecks, but also other migrants, since reasons might have to be sought elsewhere than assumed to date. Whether birds are able to temporally compensate for delays in their annual routine imposed e.g. by environmental impact and if so, to which degree, is still largely unknown. I found that hoopoes are able to compensate at least during parts of the annual cycle for ‘mistiming’ (chapter 5). Most notably the post-breeding and wintering period allowed for compensation of a late departure by decreasing the duration between the start and finish of these periods. During the pre-breeding period, birds can hardly compensate, meaning that a late arrival will lead to a later onset of SUMMARY viii breeding, which in turn leads to a slight decrease in reproductive success. Thus even though birds can compensate their timing to some extent, there is a penalty at the final stage of migration, where spring migration determines arrival and in turn reproductive success. Besides temporal flexibility, bird migration is also characterised by spatial flexibility, both of which result in a degree of individual repeatability of migratory behaviour. As I show in chapter 6, hoopoes followed the same general autumn migration directions and migrated to a similar wintering region each year, but often changed the exact wintering location and thus wintering site fidelity appears to be low. Also autumn migration timing was repeatable in both groups, contrary to spring migration. I argue that this shows that hoopoes are migrants with a high breeding site fidelity, but a relatively opportunistic behaviour outside the breeding season, perhaps profiting from very specific local conditions (e.g. wadis) and food resources (e.g. locust outbreaks). As these last two chapters show, migration might be less rigid as has been thought to date. In that respect, it is not surprising that current breeding success is affected predominantly by the previous breeding success, but only to a much lesser extent by events happening on migration (chapter 7). This suggests that the intrinsic quality of individuals plays an important role. We conclude that spring migration may influence the variation in breeding success, but that the intrinsic quality of an individual is more important to actually reproduce by gaining and defending the best territories, providing sufficient food for nestlings and maintaining the individual’s condition, thereby increasing changes of survival. Overall, hoopoes show a remarkable resilience during migration, adapting en route and in the wintering sites, both on a temporal and spatial level. Where exactly they go and which conditions are preferable, is still a black box since hardly any data is available on the exact locations of their non-breeding sites and how these relate with the dietary preferences of hoopoes (and many other migrants) in their wintering sites. Future research thus should focus on a better understanding of what happens on site during the non-breeding season and how birds prepare for the return migration to the breeding grounds. Clearly, there are advantages of departing in good condition and arriving early, but the exact mechanisms and the variation between individuals, are still poorly understood.

Abstract

SUMMARY The annual cycle of migrating birds encompasses many perils and obstacles, but it allows birds to avoid food scarcity during winters, which is common when breeding grounds are influenced by a temperate climate. Migration is thus beneficial for survival, but it may also incur fitness costs. For example, it can influence current reproductive success. To better understand the population dynamics of migrants and for their proper conservation, it is crucial to study their complete annual cycle: migration routes, timing, non-breeding sites, but also potential consequences on reproductive success. In this thesis, I studied these aspects in Hoopoes Upupa epops and Wrynecks Jynx torquilla using geolocators that were deployed between 2010-2015 on individuals of breeding populations in Southern Switzerland (Valais) and likewise used data on breeding phenology for the same time span. In order to investigate the migratory behaviour of individual birds, devices have to be used to keep track of their whereabouts. Non-invasive techniques exist, such as stable isotopes, but these techniques only give relatively poor and coarse information on the whereabouts of an individual. The use of e.g. geolocators can give more precise information, but may lead to a change in behaviour and thus also might affect migration patterns. I show in chapter 2 using an extensive set of investigated parameters, ranging from fledgling weight to apparent annual survival, that Hoopoes were not affected by carrying a geolocator with a weight corresponding to <2% of their body mass. I conclude that with the proper design and an as low as possible relative weight of a device, they can be used and give invaluable insights into detailed migratory behaviour of an individual. One aspect that is key to the understanding of population dynamics, also in the light of conservation, is where birds spend the wintering (non-breeding) season. Contrary to previous believes I show that Wrynecks from Central-European populations are short-distance migrants wintering in Northern Africa and on the Iberian Peninsula (chapter 3). Similar to their breeding grounds they prefer agricultural habitat with shrubs/orchards and patches of open, sandy soil where they can forage on ants, their main food source (chapter 4). Both findings have implications for understanding the mechanisms behind population dynamics of not only Wrynecks, but also other migrants, since reasons might have to be sought elsewhere than assumed to date. Whether birds are able to temporally compensate for delays in their annual routine imposed e.g. by environmental impact and if so, to which degree, is still largely unknown. I found that hoopoes are able to compensate at least during parts of the annual cycle for ‘mistiming’ (chapter 5). Most notably the post-breeding and wintering period allowed for compensation of a late departure by decreasing the duration between the start and finish of these periods. During the pre-breeding period, birds can hardly compensate, meaning that a late arrival will lead to a later onset of SUMMARY viii breeding, which in turn leads to a slight decrease in reproductive success. Thus even though birds can compensate their timing to some extent, there is a penalty at the final stage of migration, where spring migration determines arrival and in turn reproductive success. Besides temporal flexibility, bird migration is also characterised by spatial flexibility, both of which result in a degree of individual repeatability of migratory behaviour. As I show in chapter 6, hoopoes followed the same general autumn migration directions and migrated to a similar wintering region each year, but often changed the exact wintering location and thus wintering site fidelity appears to be low. Also autumn migration timing was repeatable in both groups, contrary to spring migration. I argue that this shows that hoopoes are migrants with a high breeding site fidelity, but a relatively opportunistic behaviour outside the breeding season, perhaps profiting from very specific local conditions (e.g. wadis) and food resources (e.g. locust outbreaks). As these last two chapters show, migration might be less rigid as has been thought to date. In that respect, it is not surprising that current breeding success is affected predominantly by the previous breeding success, but only to a much lesser extent by events happening on migration (chapter 7). This suggests that the intrinsic quality of individuals plays an important role. We conclude that spring migration may influence the variation in breeding success, but that the intrinsic quality of an individual is more important to actually reproduce by gaining and defending the best territories, providing sufficient food for nestlings and maintaining the individual’s condition, thereby increasing changes of survival. Overall, hoopoes show a remarkable resilience during migration, adapting en route and in the wintering sites, both on a temporal and spatial level. Where exactly they go and which conditions are preferable, is still a black box since hardly any data is available on the exact locations of their non-breeding sites and how these relate with the dietary preferences of hoopoes (and many other migrants) in their wintering sites. Future research thus should focus on a better understanding of what happens on site during the non-breeding season and how birds prepare for the return migration to the breeding grounds. Clearly, there are advantages of departing in good condition and arriving early, but the exact mechanisms and the variation between individuals, are still poorly understood.

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Additional indexing

Item Type:Dissertation
Referees:Keller Lukas F, Bauer Silke, Schaub Michael, Jenni Lukas, Shamoun-Baranes Judy
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Language:English
Date:2016
Deposited On:07 Nov 2016 10:52
Last Modified:15 Nov 2016 17:57

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