Theoretically possible spatial accuracy of geomagnetic maps used by migrating animals

Many migrating animals, belonging to different taxa, annually move across the globe and cover hundreds and thousands of kilometres. Many of them are able to show site fidelity, i.e. to return to relatively small migratory targets, from distant areas located beyond the possible range of direct sensory perception. One widely debated possibility of how they do it is the use of a magnetic map, based on the dependence of parameters of the geomagnetic field (total field intensity and inclination) on geographical coordinates. We analysed temporal fluctuations of the geomagnetic field intensity as recorded by three geomagnetic observatories located in Europe within the route of many avian migrants, to study the highest theoretically possible spatial resolution of the putative map. If migratory birds measure total field intensity perfectly and take the time of day into account, in northern Europe 81% of them may return to a strip of land of 43 km in width along one of coordinates, whereas in more southern areas such a strip may be narrower than 10 km. However, if measurements are performed with an error of 0.1%, the strip width is increased by approximately 40 km, so that in spring migrating birds are able to return to within 90 km of their intended goal. In this case, migrating birds would probably need another navigation system, e.g. an olfactory map, intermediate between the large-scale geomagnetic map and the local landscape cues, to locate their goal to within several kilometres.

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Where in the air? Aerial habitat use of nocturnally migrating birds

Biology Letters ◽

10.1098/rsbl.2016.0591 ◽

2016 ◽

Vol 12 (11) ◽

pp. 20160591 ◽

Cited By ~ 16

Author(s):

Kyle G. Horton ◽

Benjamin M. Van Doren ◽

Phillip M. Stepanian ◽

Andrew Farnsworth ◽

Jeffrey F. Kelly

Keyword(s):

Habitat Selection ◽

Large Scale ◽

Migratory Birds ◽

Lower Atmosphere ◽

Migration Activity ◽

Maximum Wind ◽

Eastern Usa ◽

Migrant Birds ◽

Spatio Temporal ◽

Migrating Birds

The lower atmosphere (i.e. aerosphere) is critical habitat for migrant birds. This habitat is vast and little is known about the spatio-temporal patterns of distribution and abundance of migrants in it. Increased human encroachment into the aerosphere makes understanding where and when migratory birds use this airspace a key to reducing human–wildlife conflicts. We use weather surveillance radar to describe large-scale height distributions of nocturnally migrating birds and interpret these distributions as aggregate habitat selection behaviours of individual birds. As such, we detail wind cues that influence selection of flight heights. Using six radars in the eastern USA during the spring (2013–2015) and autumn (2013 and 2014), we found migrants tended to adjust their heights according to favourable wind profit. We found that migrants' flight altitudes correlated most closely with the altitude of maximum wind profit; however, absolute differences in flight heights and height of maximum wind profit were large. Migrants tended to fly slightly higher at inland sites compared with coastal sites during spring, but not during autumn. Migration activity was greater at coastal sites during autumn, but not during spring. This characterization of bird migration represents a critical advance in our understanding of migrant distributions in flight and a new window into habitat selection behaviours.

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The importance of time of day for magnetic body alignment in songbirds

Journal of Comparative Physiology A ◽

10.1007/s00359-021-01536-9 ◽

2022 ◽

Author(s):

Giuseppe Bianco ◽

Robin Clemens Köhler ◽

Mihaela Ilieva ◽

Susanne Åkesson

Keyword(s):

Geomagnetic Field ◽

Ad Hoc ◽

Migratory Birds ◽

Learning Algorithm ◽

Underlying Mechanism ◽

Time Of Day ◽

Model Organisms ◽

Magnetic Alignment ◽

Acrocephalus Scirpaceus ◽

Compass Calibration

AbstractSpontaneous magnetic alignment is the simplest known directional response to the geomagnetic field that animals perform. Magnetic alignment is not a goal directed response and its relevance in the context of orientation and navigation has received little attention. Migratory songbirds, long-standing model organisms for studying magnetosensation, have recently been reported to align their body with the geomagnetic field. To explore whether the magnetic alignment behaviour in songbirds is involved in the underlying mechanism for compass calibration, which have been suggested to occur near to sunset, we studied juvenile Eurasian reed warblers (Acrocephalus scirpaceus) captured at stopover during their first autumn migration. We kept one group of birds in local daylight conditions and an experimental group under a 2 h delayed sunset. We used an ad hoc machine learning algorithm to track the birds’ body alignment over a 2-week period. Our results show that magnetic body alignment occurs prior to sunset, but shifts to a more northeast–southwest alignment afterwards. Our findings support the hypothesis that body alignment could be associated with how directional celestial and magnetic cues are integrated in the compass of migratory birds.

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Geomagnetic field intensity changes in the Central Mediterranean between 1500 BCE and 150 CE: Implications for the Levantine Iron Age Anomaly evolution

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2020.116732 ◽

2021 ◽

Vol 557 ◽

pp. 116732

Author(s):

M. Rivero-Montero ◽

M. Gómez-Paccard ◽

D. Kondopoulou ◽

E. Tema ◽

F.J. Pavón-Carrasco ◽

...

Keyword(s):

Iron Age ◽

Field Intensity ◽

Geomagnetic Field ◽

Central Mediterranean ◽

Intensity Changes ◽

Geomagnetic Field Intensity

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Geomagnetic field intensity from 71 to 12 ka as recorded in deep-sea sediments of the Blake Outer Ridge, North Atlantic Ocean

Journal of Geophysical Research Atmospheres ◽

10.1029/1998jb900003 ◽

1998 ◽

Vol 103 (B12) ◽

pp. 30407-30417 ◽

Cited By ~ 20

Author(s):

Martha Schwartz ◽

Steve P. Lund ◽

Thomas C. Johnson

Keyword(s):

Atlantic Ocean ◽

Field Intensity ◽

North Atlantic ◽

Deep Sea ◽

Geomagnetic Field ◽

North Atlantic Ocean ◽

Deep Sea Sediments ◽

Geomagnetic Field Intensity

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Carbon dioxide fluxes increase from day to night across European streams

Communications Earth & Environment ◽

10.1038/s43247-021-00192-w ◽

2021 ◽

Vol 2 (1) ◽

Author(s):

Katrin Attermeyer ◽

Joan Pere Casas-Ruiz ◽

Thomas Fuss ◽

Ada Pastor ◽

Sophie Cauvy-Fraunié ◽

...

Keyword(s):

Carbon Dioxide ◽

Carbon Dioxide Emissions ◽

Large Scale ◽

Carbon Dioxide Flux ◽

Time Of Day ◽

Night Time ◽

Carbon Dioxide Fluxes ◽

Large Scale Assessment ◽

Air Interface ◽

Flux Variability

AbstractGlobally, inland waters emit over 2 Pg of carbon per year as carbon dioxide, of which the majority originates from streams and rivers. Despite the global significance of fluvial carbon dioxide emissions, little is known about their diel dynamics. Here we present a large-scale assessment of day- and night-time carbon dioxide fluxes at the water-air interface across 34 European streams. We directly measured fluxes four times between October 2016 and July 2017 using drifting chambers. Median fluxes are 1.4 and 2.1 mmol m−2 h−1 at midday and midnight, respectively, with night fluxes exceeding those during the day by 39%. We attribute diel carbon dioxide flux variability mainly to changes in the water partial pressure of carbon dioxide. However, no consistent drivers could be identified across sites. Our findings highlight widespread day-night changes in fluvial carbon dioxide fluxes and suggest that the time of day greatly influences measured carbon dioxide fluxes across European streams.

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Reversals in the large-scale αΩ-dynamo with memory

Nonlinear Processes in Geophysics ◽

10.5194/npg-22-361-2015 ◽

2015 ◽

Vol 22 (4) ◽

pp. 361-369 ◽

Cited By ~ 1

Author(s):

L. K. Feschenko ◽

G. M. Vodinchar

Keyword(s):

Magnetic Field ◽

Power Law ◽

Geomagnetic Field ◽

Large Scale ◽

Magnetic Polarity ◽

Power Law Model ◽

The Real ◽

Geomagnetic Polarity ◽

With Memory ◽

The Magnetic Field

Abstract. Inversion of the magnetic field in a model of large-scale αΩ-dynamo with α-effect with stochastic memory is under investigation. The model allows us to reproduce the main features of the geomagnetic field reversals. It was established that the polarity intervals in the model are distributed according to the power law. Model magnetic polarity timescale is fractal. Its dimension is consistent with the dimension of the real geomagnetic polarity timescale.

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Standard geomagnetic observatory data in tectonomagnetism: case study related to the M 5.7 Timisoara, Romania, earthquake

Annals of Geophysics ◽

10.4401/ag-3925 ◽

1997 ◽

Vol 40 (2) ◽

Author(s):

M. Popeskov

Keyword(s):

Geomagnetic Field ◽

Large Scale ◽

Regional Scale ◽

Extensive Study ◽

Field Variation ◽

Regional Effect ◽

Data Set ◽

Small Magnitude ◽

Observatory Data ◽

Set Up

There has recently been much discussion of large-scale interactions of fault zones and the influence of large-scale processes in the preparation and triggering of earthquakes. As a consequence, an official recommendation was issued to set up observational networks at regional scale. In this context, the existing network of standard geomagnetic observatories might play a more important role in future tectonomagnetic studies. The data from standard geomagnetic observatories are basically not appropriate for the detection of small-magnitude and, in most cases, spatially very localized geomagnetic field changes. However, their advantage is a continuity in a long-time period which enables the study of regional tectonomagnetic features and long-term precursory changes. As the first step of a more extensive study aimed at examining the features of observatory data for this purpose, a three-year data set from five European observatories has been analyzed. Some common statistical procedures have been applied along with a simple difference technique and multivariate linear regression to define local geomagnetic field changes. The distribution of M ³ 4.5 earthquakes in Europe, in a corresponding period, was also taken into account. No pronounced field variation, related in time to the M 5.7 Timisoara (Romania) earthquake on July 12, 1991, was found at Grocka observatory at about 80 km from the earthquake epicenter. However, an offset in level of the differences in declination which include Grocka observatory, not seen in the case of differences between other observatories, could be associated with a possible regional effect of the M 4.8 earthquake which occurred in September 1991 at about 70 km SE from Grocka.

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A tectonomagnetic effect detected in Central Italy

Annals of Geophysics ◽

10.4401/ag-4233 ◽

1994 ◽

Vol 37 (1) ◽

Author(s):

G. Mele ◽

A. Meloni ◽

P. Palangio

Keyword(s):

Field Intensity ◽

Geomagnetic Field ◽

Central Italy ◽

Volcanic Eruptions ◽

Intensity Data ◽

Absolute Level ◽

Tectonic Events ◽

Railway System ◽

The Absolute ◽

Geomagnetic Intensity

Significant variations in the absolute value of the geomagnetic field intensity related to tectonic events, as earthquakes and volcanic eruptions, have been observed in several cases. To detect such a tectonomagnetic effect related to seismic activity, a seismomagnetic network was installed by the Istituto Nazionale di Geofisica (ING) in the Abruzzi region (CentraI Italy), in July 1989. This area is being uplifting since the Pliocene. A logistic compromise between geophysical requirements and the electrified railway system tracks distribution led to the installation of five total magnetic field intensity data acquisition sites. From July 1989 to September 1992 geomagnetic intensity data were simultaneously recorded at all stations and compared to that recorded at the L'Aquila Observatory, located in the same area. A variation of about 10 nT in the absolute level of the geomagnetic field was measured at two stations located on the eastern side of the network. We suggest that the detected magnetic anomaly could resuIt from aseismic-changes in crustal stress during this time.

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