Magnetic Disturbance seems to be gaining popularity as a cause of vagrancy, but does the Science stand scrutiny. (1 Viewer)

[Jon.Bryant]

In recent years more articles and threads seem to reference magnetic disturbance as a likely cause of vagrancy, but having read the scientific papers, does the science stand scrutiny?

Experiments have been done with birds to determine whether birds use magnetic fields to migrate, and this has shown that birds are impacted by strong magnetic fields. However, as far as I am aware, similar experiments have yet to be performed on weak changes in magnetic fields, as may for instance be caused by solar storms. These disturbances are general insufficient to upset a compass, and it would be interesting to see what effect they have on a birds orientation.

The often quoted paper is 'Geomagnetic disturbance associated with increased vagrancy in migratory landbirds' [Article Here]. To me this article does not fully stand scrutiny for the following reasons;

• It is unproven that any of the vagrants that they considered in their analysis followed a migration route that was subject to high magnetic disturbance. This may sound rather daft, but the analysis was based on the 'International Service for Geomagnetic Indices' Kp dataset. The Kp index is an average reading from 13 global geomagnetic observatories located at mid level latitudes (in fact these 13 observatories do not produce real time result, and it is therefore understood that other observatories interpolate the results for these locations). Regardless of how the Kp index is determined, a high Kp index does not mean that all areas experienced high magnetic disturbance - for example a storm in the southern hemisphere would raise the global index, whereas the northern hemisphere may be unaffected.
• The use of a 21 day rolling average for Kp also further complicates the issue as to whether the vagrant was impacted by a high magnetic field, as it then unclear if the average has been impacted by a few high results, and impossible to know if the bird was in active migration on those particular days.
• The analysis considered several species living at mid level latitudes, whereas due to the earths magnetic fields, magnetic disturbances are generally more severe towards the poles. Inclusion of species that are less likely to have been exposed to higher magnetic disturbances (and discovery of changes in migration) therefore seems questionable.
• The comments regarding diurnal and nocturnal migrants being effected differently is not properly explained. Solar storms take a variable amount of time to reach the earth. The largest flare ever recorded (the Carrington Event) took 17 hours between the observation of the flare and the magnetic storms reaching earth, which is reportedly quite fast. Magenetic storms therefore obviously impact the earth during daylight of nighttime (hence the auroras). Solar flairs also give off radio waves that travel at the speed of light, so reach the earth in circa 4 mins. These radio waves would therefore only effect diurnal migrants, facing the sun, but the blast of of the radio waves is incredibly transient at less than a second, and as far as I am aware tests have not been conducted to show that bird migration is impacted by exposure to radio waves.
• With reference to the geospace ground magnetic perturbation maps see link here. Forecasts for disturbances in magnetic field, do effect lower latitudes, but these disturbances general last very short periods - the forecast is provided at minute intervals. As far as I am aware no experiments have been conducted to show whether birds experience lag and prolonged disorientation after a short exposure to magnetic disturbance. Without this it is hard to see how even a hour of exposure would severely impact a long migration - rather than causing disorientation for a relatively short distance.

I would also add that solar activity peaks on an approximate 7 year cycle. On this basis, it would be expected that records of vagrancy should also peak on a seven year cycle. In my own review of BBRC records I have been unable to find any such 7 year cycle in the data.

A search for other articles on the subject produced 'Magnetic storms disrupt nocturnal migratory activity in songbirds' [see here], which suggests that migration of European Robin is in fact curtailed by simulated Magnetic Storms, whereas Chiffchaff and Dunnock seem unaffected (potentially as they may not rely on magnetic fields to such as large extent).

Space weather disrupts nocturnal bird migration see link here also suggests that migration is suppressed by magnetic activity, but that migration may be also impacted. However, they then say that they have not isolated the impact of weather on displacement. Weather is an obvious and known mechanism for displacement, and hence isolating the impact of weather from magnetic fluctuation, would be essential to determine if vagrancy can be caused by solar storms and magnetic variations.

There seems some logic in the concept that the loss or confusion of a sense would result in a decision not to migrate and a curtailment of activity. There seems less logic to me that a transient effect that may last minutes or perhaps an hour or so, and that generally covers a localized area (and at more extreme latitudes), would have a prolonged impact resulting in long distance vagrancy.

Do people agree or disagree? and if you agree should we stop stating that 'vagrancy can be caused by Geomagnetic disturbance' until further research is conducted. A comparison of forecast magnetic disturbance with real-time GPS or RF Tag data, that showed any change in migration direction would be extremely informative.

​

 

[jurek]

I think all such studies are more like plausible tales than proven facts. For one thing, vagrants are diverse, distantly related species - it is unlikely that all bird species have one navigation mechanism.

 

[Richard Prior]

There certainly seems to be a fair bit of supposition in the absence of hard evidence from what you’ve highlighted Jon. I agree with your concluding sentence!
On a similar theme: ‘They have no one to follow’: how migrating birds use quantum mechanics to navigate

 

[vergan]

In recent years more articles and threads seem to reference magnetic disturbance as a likely cause of vagrancy, but having read the scientific papers, does the science stand scrutiny?

Experiments have been done with birds to determine whether birds use magnetic fields to migrate, and this has shown that birds are impacted by strong magnetic fields. However, as far as I am aware, similar experiments have yet to be performed on weak changes in magnetic fields, as may for instance be caused by solar storms. These disturbances are general insufficient to upset a compass, and it would be interesting to see what effect they have on a birds orientation.

The often quoted paper is 'Geomagnetic disturbance associated with increased vagrancy in migratory landbirds' [Article Here]. To me this article does not fully stand scrutiny for the following reasons;

• It is unproven that any of the vagrants that they considered in their analysis followed a migration route that was subject to high magnetic disturbance. This may sound rather daft, but the analysis was based on the 'International Service for Geomagnetic Indices' Kp dataset. The Kp index is an average reading from 13 global geomagnetic observatories located at mid level latitudes (in fact these 13 observatories do not produce real time result, and it is therefore understood that other observatories interpolate the results for these locations). Regardless of how the Kp index is determined, a high Kp index does not mean that all areas experienced high magnetic disturbance - for example a storm in the southern hemisphere would raise the global index, whereas the northern hemisphere may be unaffected.
• The use of a 21 day rolling average for Kp also further complicates the issue as to whether the vagrant was impacted by a high magnetic field, as it then unclear if the average has been impacted by a few high results, and impossible to know if the bird was in active migration on those particular days.
• The analysis considered several species living at mid level latitudes, whereas due to the earths magnetic fields, magnetic disturbances are generally more severe towards the poles. Inclusion of species that are less likely to have been exposed to higher magnetic disturbances (and discovery of changes in migration) therefore seems questionable.
• The comments regarding diurnal and nocturnal migrants being effected differently is not properly explained. Solar storms take a variable amount of time to reach the earth. The largest flare ever recorded (the Carrington Event) took 17 hours between the observation of the flare and the magnetic storms reaching earth, which is reportedly quite fast. Magenetic storms therefore obviously impact the earth during daylight of nighttime (hence the auroras). Solar flairs also give off radio waves that travel at the speed of light, so reach the earth in circa 4 mins. These radio waves would therefore only effect diurnal migrants, facing the sun, but the blast of of the radio waves is incredibly transient at less than a second, and as far as I am aware tests have not been conducted to show that bird migration is impacted by exposure to radio waves.
• With reference to the geospace ground magnetic perturbation maps see link here. Forecasts for disturbances in magnetic field, do effect lower latitudes, but these disturbances general last very short periods - the forecast is provided at minute intervals. As far as I am aware no experiments have been conducted to show whether birds experience lag and prolonged disorientation after a short exposure to magnetic disturbance. Without this it is hard to see how even a hour of exposure would severely impact a long migration - rather than causing disorientation for a relatively short distance.

I would also add that solar activity peaks on an approximate 7 year cycle. On this basis, it would be expected that records of vagrancy should also peak on a seven year cycle. In my own review of BBRC records I have been unable to find any such 7 year cycle in the data.

A search for other articles on the subject produced 'Magnetic storms disrupt nocturnal migratory activity in songbirds' [see here], which suggests that migration of European Robin is in fact curtailed by simulated Magnetic Storms, whereas Chiffchaff and Dunnock seem unaffected (potentially as they may not rely on magnetic fields to such as large extent).

Space weather disrupts nocturnal bird migration see link here also suggests that migration is suppressed by magnetic activity, but that migration may be also impacted. However, they then say that they have not isolated the impact of weather on displacement. Weather is an obvious and known mechanism for displacement, and hence isolating the impact of weather from magnetic fluctuation, would be essential to determine if vagrancy can be caused by solar storms and magnetic variations.

There seems some logic in the concept that the loss or confusion of a sense would result in a decision not to migrate and a curtailment of activity. There seems less logic to me that a transient effect that may last minutes or perhaps an hour or so, and that generally covers a localized area (and at more extreme latitudes), would have a prolonged impact resulting in long distance vagrancy.

Do people agree or disagree? and if you agree should we stop stating that 'vagrancy can be caused by Geomagnetic disturbance' until further research is conducted. A comparison of forecast magnetic disturbance with real-time GPS or RF Tag data, that showed any change in migration direction would be extremely informative.

​

I know some experiments on ele.seals orientarions..
Are you incluing that on your ideas?

 

[Jon.Bryant]

I know some experiments on ele.seals orientarions..
Are you incluing that on your ideas?

I haven’t seen the details of the experiments.

You say ideas, but I am not sure quite what you mean? I basically do not believe that some ‘scientific’ papers stand scrutiny. I therefore think their finding are currently unproven. This does not mean that they are necessarily wrong, just further work needs to be done, before the wider public accept the findings as fact. Until that time we should treat findings with caution.