Browsing by Author "Kaatz, Michael"

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    Data from: Costs of migratory decisions: a comparison across eight white stork populations
    (2015-06-13) Flack, Andrea; Fiedler, Wolfgang; Blas, Julio; Pokrovsky, Ivan; Mitropolsky, B.; Kaatz, Michael; Aghababyan, Karen; Khachatryan, A.; Fakriadis, Ioannis; Makrigianni, Eleni; Jerzak, Leszek; Shamin, M.; Shamina, C.; Azafzaf, H.; Mokotjomela, Thabiso M.; Feltrup-Azafzaf, Claudia; Wikelski, Martin
    Annual migratory movements can range from a few tens to thousands of kilometers, creating unique energetic requirements for each specific species and journey. Even within the same species, migration costs can vary largely because of flexible, opportunistic life history strategies. We uncover the large extent of variation in the lifetime migratory decisions of young white storks originating from eight populations. Not only did juvenile storks differ in their geographically distinct wintering locations, their diverse migration patterns also affected the amount of energy individuals invested for locomotion during the first months of their life. Overwintering in areas with higher human population reduced the stork’s overall energy expenditure because of shorter daily foraging trips, closer wintering grounds, or a complete suppression of migration. Because migrants can change ecological processes in several distinct communities simultaneously, understanding their life history decisions helps not only to protect migratory species but also to conserve stable ecosystems.
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    Data from: Early arrival at breeding grounds: causes, costs and a trade-off with overwintering latitude
    (2018-09-14) Rotics, Shay; Kaatz, Michael; Turjeman, Sondra Feldman; Zurell, Damaris; Wikelski, Martin; Sapir, Nir; Eggers, Ute; Fiedler, Wolfgang; Jeltsch, Florian; Nathan, Ran
    (1) Early arrival at breeding grounds is of prime importance for migrating birds as it is known to enhance breeding success. Adults, males and higher quality individuals typically arrive earlier, and across years, early arrival has been linked to warmer spring temperatures. However, the mechanisms and potential costs of early arrival are not well understood. (2) To deepen the understanding of arrival date differences between individuals and years, we studied them in light of the preceding spring migration behaviour and atmospheric conditions en route. (3) GPS and body‐acceleration (ACC) data were obtained for 35 adult white storks (Ciconia ciconia) over five years (2012‐2016). ACC records were translated to energy expenditure estimates (Overall Dynamic Body Acceleration; ODBA) and to behavioural modes, and GPS fixes were coupled with environmental parameters. (4) At the inter‐individual level (within years), early arrival was attributed primarily to departing earlier for migration and from more northern wintering sites (closer to breeding grounds), rather than to migration speed. In fact, early departing birds flew slower, experienced weaker thermal uplifts and expended more energy during flight, but still arrived earlier, emphasizing the cost and the significance of early departure. Individuals that wintered further south arrived later at the breeding grounds but did not produce fewer fledglings, presumably due to positive carry‐over effects of advantageous wintering conditions (increased precipitation, vegetation productivity and daylight time). Therefore, early arrival increased breeding success only after controlling for wintering latitude. Males arrived slightly ahead of females. Between years, late arrival was linked to colder temperatures en route through two different mechanisms: stronger headwinds causing slower migration and lower thermal uplifts resulting in longer stopovers. (5) This study showed that distinct migratory properties underlie arrival time variation within and between years. It highlighted: (a) an overlooked cost of early arrival induced by unfavourable atmospheric conditions during migration, (b) an important fitness trade‐off in storks between arrival date and wintering habitat quality, and (c) mechanistic explanations for the negative temperature‐arrival date correlation in soaring birds. Such understanding of arrival time can facilitate forecasting migrating species responses to climate changes.
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    Data from: Study "MPIAB Argos white stork tracking (1991-2017)"
    (2022-12-26) Berthold, Peter; Kaatz, Christoph; Kaatz, Michael; Querner, Ulrich; van den Bossche, Willem; Chernetsov, Nikita; Fiedler, Wolfgang; Wikelski, Martin
    Satellite tracking of white storks (Ciconia ciconia) was begun by the Max Planck Institute of Ornithology and collaborators in 1991. After solar-powered transmitters became available in 1995, extended battery life combined with the possibility to replace transmitters over time allowed monitoring the movements of individual storks across multiple migration seasons, with one individual, Prinzesschen, tracked for over a decade. Research efforts continue using primarily GSM-based tracking technologies. This dataset includes over 200 storks tagged in Belgium, Germany, Greece, Israel, Poland, Russia, South Africa, Spain and Switzerland. As noted in the deployment information, some movements are influenced by experimental manipulations. This long-term study confirms what previous several-year tracking studies of white storks had indicated: there can be great variability from year to year in the choice of winter quarters as well as in the routes and times of migration, intermediate destinations and stop-over periods, but constancy of winter quarters and migration routes is also possible. The variability may well be caused by external factors, of which food supply is probably predominant.
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    Data from: The challenges of the first migration: movement and behavior of juvenile versus adult white storks with insights regarding juvenile mortality
    (2016-04-12) Rotics, Shay; Kaatz, Michael; Resheff, Yehezkel S.; Turjeman, Sondra Feldman; Zurell, Damaris; Sapir, Nir; Eggers, Ute; Flack, Andrea; Fiedler, Wolfgang; Jeltsch, Florian; Wikelski, Martin; Nathan, Ran
    (1) Migration conveys an immense challenge especially for juvenile birds coping with enduring and risky journeys shortly after fledging. Accordingly, juveniles exhibit considerably lower survival rates compared to adults, particularly during migration. Also, juvenile white storks (Ciconia ciconia), which are known to rely on adults during their first fall migration, presumably for navigational purposes, display much lower annual survival than adults. (2) Using detailed GPS and body acceleration data, we examined the patterns and potential causes of age-related differences in fall migration properties of white storks by comparing first-year juveniles and adults. We compared juvenile and adult parameters of movement, behavior and energy expenditure (estimated from overall dynamic body acceleration, ODBA) and placed this in the context of the juveniles’ lower survival rate. (3) Juveniles used flapping flight versus soaring flight 23% more than adults and were estimated to expend 14% more energy during flight. Juveniles did not compensate for increased flight costs by increased refueling or resting during migration. When juveniles and adults migrated together in the same flock, the juvenile flew mostly behind the adult and was left behind when they separated. Juveniles showed greater improvement in flight efficiency throughout migration compared to adults which appears crucial because juveniles exhibiting higher flight costs suffered increased mortality. (4) Our findings demonstrate the conflict between the juveniles’ inferior flight skills and their urge to keep up with mixed adult-juvenile flocks. We suggest that increased flight costs are an important proximate cause of juvenile mortality in white storks and likely in other soaring migrants, and that natural selection is operating on juvenile variation in flight efficiency.