Fuelling decisions in migratory birds: geomagnetic cues override the seasonal effect

Kullberg, Cecilia; Henshaw, Ian; Jakobsson, Sven; Johansson, Patrik; Fransson, Thord

doi:10.1098/rspb.2007.0554

Cited by 48 publications

(40 citation statements)

References 40 publications

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“…It might be argued that birds exposed to the magnetic field of northern Egypt do not react to the magnetic field of Egypt per se, but that any change in the magnetic field causes chronic stress resulting in a reduced adrenocortical response and hyperphagia. In an earlier study we have, however, shown that European robins (Erithacus rubecula), being medium-distance migrants, reduce their fuel deposition rate in a biologically relevant way as a result of a magnetically simulated migratory journey from Sweden to their wintering area in Spain compared with control birds experiencing the ambient magnetic field of Sweden (Kullberg et al, 2007). This nicely illustrates that a reduction in magnetic field intensity and inclination (a southward flight from Sweden) does not induce a general stress response causing hyperphagia in migratory birds but, rather, triggers either an increase or a decrease in fuel deposition rate depending on the biological relevance for the species.…”

Section: Discussionmentioning

confidence: 99%

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Information from the geomagnetic field triggers a reduced adrenocortical response in a migratory bird

Henshaw

Fransson

Jakobsson

et al. 2009

Journal of Experimental Biology

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SUMMARYLong-distance migrants regularly pass ecological barriers, like the Sahara desert, where extensive fuel loads are necessary for a successful crossing. A central question is how inexperienced migrants know when to put on extensive fuel loads. Beside the endogenous rhythm, external cues have been suggested to be important. Geomagnetic information has been shown to trigger changes in foraging behaviour and fuel deposition rate in migratory birds. The underlying mechanism for these adjustments, however, is not well understood. As the glucocorticoid hormone corticosterone is known to correlate with behaviour and physiology related to energy regulation in birds, we here investigated the effect of geomagnetic cues on circulating corticosterone levels in a long-distance migrant. Just as in earlier studies, juvenile thrush nightingales (Luscinia luscinia) caught during autumn migration and exposed to the simulated geomagnetic field of northern Egypt increased food intake and attained higher fuel loads than control birds experiencing the ambient magnetic field of southeast Sweden. Our results further show that experimental birds faced a reduced adrenocortical response compared with control birds, thus for the first time implying that geomagnetic cues trigger changes in hormonal secretion enabling appropriate behaviour along the migratory route.

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Section: Discussionmentioning

confidence: 99%

“…The system consisted of three independent series of four quadratic coils each, arranged to control the X-(north-south), Y-(east-west) and Z-components (vertical) of the magnetic field. For further information on the magnetic coil systems see Kullberg et al (Kullberg et al, 2007).…”

Section: The Magnetic Coilsmentioning

confidence: 99%

Information from the geomagnetic field triggers a reduced adrenocortical response in a migratory bird

Henshaw

Fransson

Jakobsson

et al. 2009

Journal of Experimental Biology

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“…Mostly, endogenous mechanisms have been thought to control various aspects of a migrant's physiology and behaviour including both timing and amount of fuelling during migration (Berthold, 1996). Recent evidence now strongly suggests that temporal and spatial precision of bird migration incorporates additional external cues along with the inherited migratory program (Fransson et al, 2001; Thorup and Rabøl, 2001;Jenni and Schaub, 2003;Fransson et al, 2005;Alerstam, 2006;Kullberg et al, 2007). In order to find confined species-specific areas it seems likely that birds must use some additional external cues in combination with clock-and-compass orientation (Fransson et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Food intake and fuel deposition in a migratory bird is affected by multiple as well as single-step changes in the magnetic field

Henshaw

Fransson

Jakobsson

et al. 2008

Journal of Experimental Biology

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SUMMARYRecent studies have shown that migratory thrush nightingales (Luscinia luscinia) experimentally treated with multiple changes of the magnetic field simulating a journey to their target stopover area in northern Egypt, increased fuel deposition as expected in preparation to cross the Sahara desert. To investigate the significance of food intake on the body mass changes observed, in the work described here we analysed food intake of the nightingales under study in those earlier experiments. Furthermore, to study whether a single change in the magnetic field directly to northern Egypt is sufficient to provide information for fuelling decisions, we performed a new experiment, exposing thrush nightingales trapped in Sweden, directly to a magnetic field of northern Egypt. Our results show that an experimentally induced magnetic field of northern Egypt, close to the barrier crossing, triggers the same response in fuel deposition as experiments with multiple changes of the magnetic field simulating a migratory journey from Sweden to Egypt, suggesting that migratory birds do not require successive changes in field parameters to incorporate magnetic information into their migratory program. Furthermore, irrespective of experimental set up (single or multiple changes of the magnetic field parameters) increase in food intake seems to be the major reason for the observed increase in fuelling rate compared with control birds, suggesting that geomagnetic information might trigger hormonal changes in migratory birds enabling appropriate fuelling behaviour during migration.

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“…Regarding day length cues, captive birds can be induced into the migratory condition by manipulating day length (Landys et al 2004a). Regarding geomagnetic cues, simulated displacement along the migratory route by artificial changes in the geomagnetic field affects fuel preparation (Fransson et al 2001;Kullberg et al 2007;Henshaw et al 2008) and orientation behaviour (Henshaw et al 2010) of captive birds and thus may affect their motivation to resume migration. Probably by changing the plasma corticosterone level of the birds, these external cues could trigger the endogenous system to regulate the migratory restlessness (Landys et al 2004a;Lõhmus et al 2003).…”

Section: Intensity Of Migratory Activitymentioning

confidence: 99%

Springtime migratory restlessness and departure orientation of Great Knots (Calidris tenuirostris) in the south compared to the north Yellow Sea

et al. 2017

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Background:The motivation of birds to proceed with migration is associated with both endogenous and exogenous factors. According to their migratory situation and to the characteristics of stopover sites, birds might exhibit migratory motivation differently among sites. Although migratory motivation of migrating birds has been well studied in many species, the investigation of the same species in different migratory situations and at different stopover sites is still limited. We predicted that birds at different stopover sites could differ in migratory disposition, including expression of migratory restlessness and responses to environmental cues. Methods:Here we compared migration motivation and orientation of Great Knots (Calidris tenuirostris) at two stopover sites, Chongming Dongtan in the south Yellow Sea, which is a temporary rest site, and Yalujiang Estuary Wetland in the north Yellow Sea, which is a critical refuelling site, during northward migration. Modified Emlen funnels, with thermal paper inside to record scratches of the birds, were used to detect activity (intensity and direction) of birds. Environmental conditions, including wind direction and speed, cloud cover, tide condition, times of the day (before and after sunset) were recorded during experiments. Generalized linear models were used to detect the effects of endogenous and exogenous factors on the migratory motivation of the birds. Results:In the south Yellow Sea, the migratory activity intensity of Great Knots was positively related to wind assistance. In the north Yellow Sea, where birds exhibited higher intensity of migratory activity than in the south, the intensity increased and the motivation to initiate migration grew stronger as the season advanced. The Great Knots exhibited wind-related orientation behaviour in the funnels at both sites. Conclusions:The results suggest that the intensity of migratory motivation differed between the two sites. Departure decisions of Great Knots appear to be affected mainly by external factors at the temporary rest site in the south Yellow Sea but possibly by endogenous factors at the final pre-breeding refuelling site in the north Yellow Sea.

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Fuelling decisions in migratory birds: geomagnetic cues override the seasonal effect

Cited by 48 publications

References 40 publications

Information from the geomagnetic field triggers a reduced adrenocortical response in a migratory bird

Information from the geomagnetic field triggers a reduced adrenocortical response in a migratory bird

Food intake and fuel deposition in a migratory bird is affected by multiple as well as single-step changes in the magnetic field

Springtime migratory restlessness and departure orientation of Great Knots (Calidris tenuirostris) in the south compared to the north Yellow Sea

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