| 1. |
- Bäckman, Johan, et al.
(författare)
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Activity and migratory flights of individual free-flying songbirds throughout the annual cycle : Method and first case study
- 2017
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Ingår i: Journal of Avian Biology. - : Wiley. - 0908-8857. ; 48:2, s. 309-319
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Tidskriftsartikel (refereegranskat)abstract
- We describe a method and device (< 1.2 g) for recording, processing and storing data about activity and location of individuals of free-living songbirds throughout the annual cycle. Activity level was determined every five minutes from five 100 ms samples of accelerometer data with 5 s between the sampling events. Activity levels were stored on an hourly basis throughout the annual cycle, allowing periods of resting/sleep, continuous flight and intermediate activity (foraging, breeding) to be distinguished. Measurements from a light sensor were stored from preprogrammed key stationary periods during the year to provide control information about geographic location. Successful results, including annual actogram, were obtained for a red-backed shrike Lanius collurio carrying out its annual loop migration between northern Europe and southern Africa. The shrike completed its annual migration by performing > 66 (max. 73) nocturnal migratory flights (29 flights in autumn and > 37, max. 44, in spring) adding up to a total of > 434 (max. 495) flight hours. Migratory flights lasted on average 6.6 h with maximum 15.9 h. These flights were aggregated into eight travel episodes (periods of 4-11 nights when flights took place on the majority of nights). Daytime resting levels were much higher during the winter period compared to breeding and final part of spring migration. Daytime resting showed peaks during days between successive nocturnal flights across Sahara, continental Africa and the Arabian Peninsula, indicating that the bird was mostly sleeping between these long migratory flights. Annual activity and flight data for free-living songbirds will open up many new research possibilities. Main topics that can be addressed are e.g. migratory flight performance (total flight investment, numbers and characteristics of flights), timing of stationary periods, activity patterns (resting/sleep, activity level) in different phases of the annual cycle and variability in the annual activity patterns between and within individuals.
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| 2. |
- Iwajomo, Soladoye B., et al.
(författare)
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Intra-African movements of the African cuckoo Cuculus gularis as revealed by satellite telemetry
- 2018
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Ingår i: Journal of Avian Biology. - : Wiley. - 0908-8857. ; 49:1
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Tidskriftsartikel (refereegranskat)abstract
- Despite many bird species migrating regularly within the African continent, in response to rainfall and breeding opportunities, documented evidence of the spatiotemporal patterns of such movements is scarce. We use satellite telemetry to document the year round movement of an intra-African migrant breeding in the savannah zone of sub-Saharan Africa, the African cuckoo. After breeding in central Nigeria, the birds migrated to more forested sites in the Adamawa region of Cameroon (n = 2) and western Central African Republic (n = 1). Departure from the breeding ground coincided with deteriorating environmental conditions whereas arrival at the non-breeding sites matched period of increasing vegetation greenness. Migratory movements generally occurred during dark hours. In total, an average distance of 748 km in 66 d was covered during the post-breeding migration and 744 km in 27 d during return journey with considerable individual variation and with more stopover sites used during post-breeding migration. The diversity of migration routes followed suggests a relatively variable or flexible initial migration strategy, high individual route consistency as well as high fidelity for non-breeding grounds.
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| 3. |
- Jiguet, Frederic, et al.
(författare)
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Desert crossing strategies of migrant songbirds vary between and within species
- 2019
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Each year, billions of songbirds cross large ecological barriers during their migration. Understanding how they perform this incredible task is crucial to predict how global change may threaten the safety of such journeys. Earlier studies based on radar suggested that most songbirds cross deserts in intermittent flights at high altitude, stopping in the desert during the day, while recent tracking with light loggers suggested diurnal prolongation of nocturnal flights and common non-stop flights for some species. We analyzed light intensity and temperature data obtained from geolocation loggers deployed on 130 individuals of ten migratory songbird species, and show that a large variety of strategies for crossing deserts exists between, but also sometimes within species. Diurnal stopover in the desert is a common strategy in autumn, while most species prolonged some nocturnal flights into the day. Nonstop flights over the desert occurred more frequently in spring than in autumn, and more frequently in foliage gleaners. Temperature recordings suggest that songbirds crossed deserts with flight bouts performed at various altitudes according to species and season, along a gradient ranging from low above ground in autumn to probably >2000 m above ground level, and possibly at higher altitude in spring. High-altitude flights are therefore not the general rule for crossing deserts in migrant songbirds. We conclude that a diversity of migration strategies exists for desert crossing among songbirds, with variations between but also within species.
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| 4. |
- Lerche-Jørgensen, Mathilde, et al.
(författare)
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Early returning long-distance migrant males do pay a survival cost
- 2018
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 8:23, s. 11434-11449
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Tidskriftsartikel (refereegranskat)abstract
- Timing of return to the breeding area presumably optimizes breeding output in migrants. How timing affects the other components of fitness — survival, has been comparatively little studied. Returning too early in spring is expected to be associated with high mortality in insectivorous migrants when weather conditions are still unsuitable. Yet, males in particular arrive early to get access to the best territories which have been suggested to cause arrival before it is optimal for their survival. For the outward migration in autumn, timing is presumably less directly associated with reproduction and fitness and how it might affect survival is not well understood. We use data of eight songbird species ringed across Denmark to investigate how timing of return migration in spring and departure migration in autumn close to the breeding areas affects survival for short- and long-distance migrants. Further, we compare survival optimum to the timing of males and females at a stopover site in Denmark in three sexually dimorphic, protandric species. We find a clear relationship between return migration and survival which differs between short- and long-distance migrants: Survival decreases with date for short-distance migrants and a bell-shaped relationship, with low survival for earliest and latest individuals, for long-distance migrants. In protandric species, the majority of males return before survival is optimal, whereas females on average return close to the survival optimum. The pattern of survival in relation to autumn timing is less clear, although a similar bell-shaped relationship is suggested for long-distance migrants. Our findings support the predicted mortality consequences of too early return to the breeding grounds and also that selection for early return in males leads to suboptimal migration timing regarding survival.
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| 5. |
- Lomas Vega, Marta, et al.
(författare)
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Local weather, food resources and breeding stage influence Thrush Nightingale movement
- 2018
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Ingår i: Ornis Fennica. - 0030-5685. ; 95:4, s. 151-159
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Tidskriftsartikel (refereegranskat)abstract
- Insectivorous migrants breeding at northern latitudes often time the breeding period with the seasonal peak of food resources. Whether this general pattern transfers to movement behaviour during the breeding season requires detailed study from a local perspective. We investigated fine-scale environmental correlates of movements by six actively-breeding adult Thrush Nightingales (Luscinia luscinia) at a breeding site in Denmark, using radio tracking and multiple regression models. Overall, the chick-rearing period coincided with the peak of vegetation greenness at the site. Adults flew further from nesting areas during stable weather and as vegetation greenness decreased. Adults were more active at higher environmental temperatures and when fledglings were older but still dependent on adults. These changes in local movements likely reflect adjustments to chick developmental needs and to specific local environmental conditions, including resource availability.
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| 6. |
- Lomas Vega, Marta, et al.
(författare)
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Migration Strategies of Iberian Breeding White-Rumped Swifts Apus caffer, Rufous-Tailed Scrub-Robins Cercotrichas galactotes and Bluethroats Cyanecula svecica
- 2019
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Ingår i: Ardeola (Madrid). - : Ardeola. - 0570-7358. ; 66:1, s. 51-64
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Tidskriftsartikel (refereegranskat)abstract
- The migration strategies of smaller, south European, Mediterranean birds are less well known than those of northern and central European birds. We used geolocators to map individual spatio-temporal migration schedules of three species breeding in the Iberian Peninsula: the White-rumped Swift Apus caffer, Rufous-tailed Scrub-robin Cercotrichas galactotes and Bluethroat Cyanecula svecica. The three species crossed the Sahara desert with a westward detour, to reach West African winter grounds in the Sahel (Bluethroats and Scrub-robins) or the rainforest belt (Swifts). Despite the proximity of the breeding grounds to the desert barrier, all but one individual stopped over before the desert crossing during autumn migration. After spending six months on average in sub-Saharan Africa with variable itinerancy, spring migration was faster overall and more direct than in autumn. Autumn migration was of similar duration to that found in related northern European migrants and therefore slower in southern birds. Spring migration was completed in less time than in the northern migrants (data only for Swifts and Scrub-robins). The shorter migration distance and proximity to the barrier potentially allow south European trans-Saharan migrants to migrate more slowly than northern migrants but only when less time-constrained in autumn.
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| 7. |
- Pedersen, Lykke, et al.
(författare)
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Sex-specific difference in migration schedule as a precursor of protandry in a long-distance migratory bird
- 2019
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Ingår i: Science of Nature. - : Springer Science and Business Media LLC. - 0028-1042 .- 1432-1904. ; 106:7-8
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Tidskriftsartikel (refereegranskat)abstract
- Protandry, the earlier arrival of males at the breeding grounds relative to females, is common in migratory birds. However, due to difficulties in following individual birds on migration, we still lack knowledge about the spatiotemporal origin of protandry during the annual cycle, impeding our understanding of the proximate drivers of this phenomenon. Here, we use full annual cycle tracking data of red-backed shrikes Lanius collurio to investigate the occurrence of sex-related differences in migratory pattern, which could be viewed as precursors (proximate causes) to protandry. We find protandry with males arriving an estimated 8.3 days (SE = 4.1) earlier at the breeding area than females. Furthermore, we find that, averaged across all departure and arrival events throughout the annual cycle, males migrate an estimated 5.3 days earlier than females during spring compared to 0.01 days in autumn. Event-wise estimates suggest that a divergence between male and female migratory schedules is initiated at departure from the main non-breeding area, thousands of kilometres from-, and several months prior to arrival at the breeding area. Duration of migration, flight speed during migration and spatial locations of stationary sites were similar between sexes. Our results reveal that protandry might arise from sex-differential migratory schedules emerging at the departure from the main non-breeding area in southern Africa and retained throughout spring migration, supporting the view that sex-differential selection pressure operates during spring migration rather than autumn migration.
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| 8. |
- Sjöberg, Sissel, et al.
(författare)
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Barometer logging reveals new dimensions of individual songbird migration
- 2018
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Ingår i: Journal of Avian Biology. - : Wiley. - 0908-8857. ; 49:9
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Tidskriftsartikel (refereegranskat)abstract
- Recent advances in tracking technology are based on the use of miniature sensors for recording new aspects of individual migratory behaviour. In this study, we have used activity data loggers with barometric and temperature sensors to record the flight altitudes as well as ground elevations during stationary periods of migratory songbirds. We tracked one individual of red-backed shrike and one great reed warbler along their autumn migration from Europe to Africa. Both individuals performed their migration stepwise in travel segments and climbed most metres during the passage across the Mediterranean Sea and the Sahara Desert and least metres during the first flight segment in Europe. The great reed warbler reached its highest flight altitude of 3950 m a.s.l. during the travel segment from Europe to west Africa, while the red-backed shrike reached 3650 m a.s.l as maximum flight altitude during its travel segment from Sahel to southern Africa. Both individuals used both lowlands and highlands for resting periods along their migrations. Furthermore, temperature decreased with increasing altitude during migratory flights for both individuals, highlighting the potential to determine flight duration from temperature measurements. Finally, we discuss how barometric data could be used to investigate birds’ responses to changes in air pressure as a cue for departures on migratory flights. This new technique, i.e. using a miniature data logger with barometric pressure sensor to estimate flight altitudes and ground elevations, will open up new avenues for research and importantly advance our understanding on how small birds behave during migratory flights.
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| 9. |
- Thorup, Kasper, et al.
(författare)
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Resource tracking within and across continents in long-distance bird migrants
- 2017
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Migratory birds track seasonal resources across and between continents. We propose a general strategy of tracking the broad seasonal abundance of resources throughout the annual cycle in the longest-distance migrating land birds as an alternative to tracking a certain climatic niche or shorter-term resource surplus occurring, for example, during spring foliation. Whether and how this is possible for complex annual spatiotemporal schedules is not known. New tracking technology enables unprecedented spatial and temporal mapping of long-distance movement of birds. We show that three Palearctic-African species track vegetation greenness throughout their annual cycle, adjusting the timing and direction of migratory movements with seasonal changes in resource availability over Europe and Africa. Common cuckoos maximize the vegetation greenness, whereas red-backed shrikes and thrush nightingales track seasonal surplus in greenness. Our results demonstrate that the longest-distance migrants move between consecutive staging areas even within the wintering region in Africa to match seasonal variation in regional climate. End-of-century climate projections indicate that optimizing greenness would be possible but that vegetation surplus might be more difficult to track in the future.
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| 10. |
- van Toor, Mariëlle L., et al.
(författare)
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Flexibility of habitat use in novel environments : insights from a translocation experiment with lesser black-backed gulls
- 2017
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Ingår i: Royal Society Open Science. - : The Royal Society. - 2054-5703. ; 4:1, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- Being faced with unknown environments is a concomitant challenge of species' range expansions. Strategies to cope with this challenge include the adaptation to local conditions and a flexibility in resource exploitation. The gulls of the Larus argentatus-fuscus-cachinnans group form a system in which ecological flexibility might have enabled them to expand their range considerably, and to colonize urban environments. However, on a population level both flexibility and local adaptation lead to signatures of differential habitat use in different environments, and these processes are not easily distinguished. Using the lesser black-backed gull (Larus fuscus) as a system, we put both flexibility and local adaptation to a test. We compare habitat use between two spatially separated populations, and use a translocation experiment during which individuals were released into novel environment. The experiment revealed that on a population-level flexibility best explains the differences in habitat use between the two populations. We think that our results suggest that the range expansion and huge success of this species complex could be a result of its broad ecological niche and flexibility in the exploitation of resources. However, this also advises caution when using species distribution models to extrapolate habitat use across space.
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| 11. |
- Vega, Marta Lomas, et al.
(författare)
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First-time migration in juvenile common cuckoos documented by satellite tracking
- 2016
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:12
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Tidskriftsartikel (refereegranskat)abstract
- Being an obligate parasite, juvenile common cuckoos Cuculus canorus are thought to reach their African wintering grounds from Palearctic breeding grounds without guidance from experienced conspecifics but this has not been documented. We used satellite tracking to study naïve migrating common cuckoos. Juvenile cuckoos left breeding sites in Finland moving slowly and less consistently directed than adult cuckoos. Migration of the juveniles (N = 5) was initiated later than adults (N = 20), was directed toward the southwest-significantly different from the initial southeast direction of adults-and included strikingly long Baltic Sea crossings (N = 3). After initial migration of juvenile cuckoos toward Poland, the migration direction changed and proceeded due south, directly toward the winter grounds, as revealed by a single tag transmitting until arrival in Northwest Angola where northern adult cuckoos regularly winter. Compared to adults, the juvenile travelled straighter and faster, potentially correcting for wind drift along the route. That both migration route and timing differed from adults indicates that juvenile cuckoos are able to reach proper wintering grounds independently, guided only by their innate migration programme.
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| 12. |
- Williams, Heather M., et al.
(författare)
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Common Cuckoo home ranges are larger in the breeding season than in the non-breeding season and in regions of sparse forest cover
- 2016
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Ingår i: Journal of Ornithology. - : Springer Science and Business Media LLC. - 2193-7192 .- 2193-7206. ; 157:2, s. 461-469
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Tidskriftsartikel (refereegranskat)abstract
- Knowledge of species’ habitat requirements can be gained from studying individual variation in home range size, under the assumption that larger home ranges reflect increased resource needs or decreased habitat quality. We used satellite telemetry to delineate home ranges of South Scandinavian Common Cuckoos (Cuculus canorus) throughout their annual cycle. Annual stage (breeding or non-breeding period) and percentage of forest cover were good predictors of home range size. Average breeding season home ranges were ten times as large as those of non-breeding home ranges, suggesting strong temporal variation in the birds’ resource needs, and perhaps lower habitat quality in the breeding range compared to the African part of their annual range. Furthermore, although the Cuckoos rarely chose a home range with complete forest cover, we found a significant negative relationship between forest cover and home range area. This suggests that heterogeneous landscapes which include some dense forest cover constitute important habitat for Cuckoos, and that the continuing trend of forest loss in tropical Africa could reduce habitat quality for the Cuckoo in the non-breeding season.
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