Summaries of important papers that cover animal navigation

Bauer, S., Shamoun-Baranes, J., Nilsson, C., Farnsworth, A., Kelly, J. F., Reynolds, D. R., Dokter, A. M., Krauel, J. F., Petterson, L. B., Horton, K. G. & Chapman, J. W. 2019 The grand challenges of migration ecology that radar aeroecology can help answer. Ecography42, 861-875. doi: 10.1111/ecog.04083. Bauer9 2019 

Many migratory species have experienced substantial declines that resulted from rapid and massive expansions of human structures and activities, habitat alterations and climate change. Migrants are also recognized as an integral component of biodiversity and provide a multitude of services and disservices that are relevant to human agriculture, economy and health. The plethora of recently published studies reflects the need for better fundamental knowledge on migrations and for better management of their ecological and human-relevant effects. Yet, where are we in providing answers to fundamental questions and societal challenges? Engaging a broad network of researchers worldwide, we used a horizon-scan approach to identify the most important challenges which need to be overcome in order to gain a fuller understanding of migration ecology, and which could be addressed using radar aeroecological and macroecological approaches. The top challenges include both long-standing and novel topics, ranging from fundamental information on migration routes and phenology, orientation and navigation strategies, and the multitude of effects migrants may have on resident communities, to societal challenges, such as protecting or preventing migrant services and disservices, and the conservation of migrants in the face of environmental changes. We outline these challenges, identify the urgency of addressing them and the primary stakeholders – researchers, policy makers and practitioners, or funders of research.

Nilsson, C., Dokter, A. M., Verlinden, L., Shamoun-Baranes, J., Schmid, B., Desmet, P., Bauer, S., Chapman, J., Alves, J. A., Stepanian, P. M., Sapir, N., Wainwright, C., Boos, M., Górska, A., Menz, M. H. M., Rodrigues, P., Leijnse, H., Zehtindjiev, P., Brabant, R., Haase, G., Weisshaupt, N., Ciach, M. & Liechti, F. 2019 Revealing patterns of nocturnal migration using the European weather radar network. Ecography42, 876-886. doi: 10.1111/ecog.04003. Nilsson10 2019 

Nocturnal avian migration flyways remain an elusive concept, as we have largely lacked methods to map their full extent. We used the network of European weather radars to investigate nocturnal bird movements at the scale of the European flyway. We mapped the main migration directions and showed the intensity of movement across part of Europe by extracting biological information from 70 weather radar stations from northern Scandinavia to Portugal, during the autumn migration season of 2016. On average, over the 20 nights and all sites, 389 birds passed per 1 km transect per hour. The night with highest migration intensity showed an average of 1621 birds km–1 h–1 passing the radar stations, but there was considerable geographical and temporal variation in migration intensity. The highest intensity of migration was seen in central France. The overall migration directions showed strong southwest components. Migration dynamics were strongly related to synoptic wind conditions. A wind-related mass migration event occurred immediately after a change in wind conditions, but quickly diminished even when supporting winds continued to prevail. This first continental-scale study using the European network of weather radars demonstrates the wealth of information available and its potential for investigating large-scale bird movements, with consequences for ecosystem function, nutrient transfer, human and livestock health, and civil and military aviation.

Hüppop, O., Ciach, M., Diehl, R., Reynolds, D. R., Stepanian, P. M. & Menz, M. H. M. 2019 Perspectives and challenges for the use of radar in biological conservation. Ecography42, 912-930. doi: 10.1111/ecog.04063. 

Hüppop1 2019 Radar is at the forefront for the study of broad-scale aerial movements of birds, bats and insects and related issues in biological conservation.

Radar techniques are especially useful for investigating species which fly at high altitudes, in darkness, or which are too small for applying electronic tags. Here, we present an overview of radar applications in biological conservation and highlight its future possibilities. Depending on the type of radar, information can be gathered on local- to continental-scale movements of airborne organisms and their behaviour. Such data can quantify flyway usage, biomass and nutrient transport (bioflow), population sizes, dynamics and distributions, times and dimensions of movements, areas and times of mass emergence and swarming, habitat use and activity ranges. Radar also captures behavioural responses to anthropogenic disturbances, artificial light and man-made structures. Weather surveillance and other long-range radar networks allow spatially broad overviews of important stopover areas, songbird mass roosts and emergences from bat caves. Mobile radars, including repurposed marine radars and commercially dedicated ‘bird radars’, offer the ability to track and monitor the local movements of individuals or groups of flying animals. Harmonic radar techniques have been used for tracking short-range movements of insects and other small animals of conservation interest. However, a major challenge in aeroecology is determining the taxonomic identity of the targets, which often requires ancillary data obtained from other methods. Radar data have become a global source of information on ecosystem structure, composition, services and function and will play an increasing role in the monitoring and conservation of flying animals and threatened habitats worldwide.

Ferguson, A., Reed, T. E., Cross, T. F., Mcginnity, P. & Prodöhl, P. A. 2019 Anadromy, potamodromy and residency in brown trout Salmo trutta: the role of genes and the environment. Journal of Fish Biology0. doi: 10.1111/jfb.14005. Ferguson6 2019 

Brown trout Salmo trutta is endemic to Europe, western Asia, north-western Africa and is a prominent member of freshwater and coastal marine fish faunas. The species shows two resident (river-resident, lake-resident) and three main facultative migratory life histories (downstream–upstream within a river system, fluvial–adfluvial potamodromous; to and from a lake, lacustrine–adfluvial (inlet)–allucustrine (outlet) potamodromous; to and from the sea, anadromous). River-residency v. migration is a balance between enhanced feeding and thus growth advantages of migration to a particular habitat v. the costs of potentially greater mortality and energy expenditure. Fluvial–adfluvial migration usually has less feeding improvement, but less mortality risk, than lacustrine–adfluvial–allacustrine and anadromous, but the latter vary among catchments as to which is favoured. Indirect evidence suggests that around 50% of the variability in S. trutta migration v. residency, among individuals within a population, is due to genetic variance. This dichotomous decision can best be explained by the threshold-trait model of quantitative genetics. Thus, an individual’s physiological condition (e.g., energy status) as regulated by environmental factors, genes and non-genetic parental effects, acts as the cue. The magnitude of this cue relative to a genetically predetermined individual threshold, governs whether it will migrate or sexually mature as a river-resident. This decision threshold occurs early in life and, if the choice is to migrate, a second threshold probably follows determining the age and timing of migration. Migration destination (mainstem river, lake, or sea) also appears to be genetically programmed. Decisions to migrate and ultimate destination result in a number of subsequent consequential changes such as parr–smolt transformation, sexual maturity and return migration. Strong associations with one or a few genes have been found for most aspects of the migratory syndrome and indirect evidence supports genetic involvement in all parts. Thus, migratory and resident life histories potentially evolve as a result of natural and anthropogenic environmental changes, which alter relative survival and reproduction. Knowledge of genetic determinants of the various components of migration in S. trutta lags substantially behind that ofOncorhynchus mykiss and other salmonids. Identification of genetic markers linked to migration components and especially to the migration–residency decision, is a prerequisite for facilitating detailed empirical studies. In order to predict effectively, through modelling, the effects of environmental changes, quantification of the relative fitness of different migratory traits and of their heritabilities, across a range of environmental conditions, is also urgently required in the face of the increasing pace of such changes. 

If you want to read any of the whole papers, copy the title into Google and you will find it listed.

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Discovery of a human geomagnetic sensory system | Human Frontier Science Program

This link is fascinating and shows that humans can sense the magnetic field even if they do not know that they have. We already know that a lot of animal navigation takes place in the hippocampus i.e. in the Subconscious.

Could this mean that there might be a correlation with the way that humans react to the magnetic field?  
Does sensing the magnetic field help those who profess that they do have sense of direction?

I have been amazed that if you ask most people if they have sense of direction you get a binary result:

  • Yes I do and use it all the time
  • No I do not

I would expect a more nuanced answer

Richard Nissen, Editor

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Physical limits to magneto genetics – Markus Meister

This is an analysis of how magnetic fields affect biological molecules and cells. It was prompted by a series of prominent reports regarding magnetism in biological systems. The first claims to have identified a protein complex that acts like a compass needle to guide magnetic orientation in animals (Qin et al., 2016). Two other articles report magnetic control of membrane conductance by attaching ferritin to an ion channel protein and then tugging the ferritin or heating it with a magnetic field (Stanley et al., 2015; Wheeler et al., 2016). Here I argue that these claims conflict with basic laws of physics. The discrepancies are large: from 5 to 10 log units. If the reported phenomena do in fact occur, they must have causes entirely different from the ones proposed by the authors. The paramagnetic nature of protein complexes is found to seriously limit their utility for engineering magnetically sensitive cells.

Here is the full article as published in eLife: Meister1 2016

Division of Biology and Biological Engineering

California Institute of Technology
Pasadena, CA 91125
[email protected]

Competing interests: No competing interests were disclosed.

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Ways pigeons might home

Here is a fascinating YouTube video discussing different ways a pigeon might home.

The people shown here are our heroes, who are really important people in the animal navigation world and especially in Pigeon navigation.

You will find Tim Guildford at Oxford University, who believes that pigeons follow landmarks, The Wiltchokos who believe in magnetic cues, Anna Galgiardo who says it is all to do with smell and Rupert Sheldrake who has the idea of Morphic resonance: here, the pigeons have a connection to their loft.

Richard Nissen

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Animal Navigation poster for RIN19

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Do you have a sense of direction?

There is a lot of work going on in the navigation field.  All the researchers in this field are now clear that navigation takes place in the sub-conscious.  I made the mistake of thinking that native peoples who seemed to navigate perfectly without any aids could tell me how they did it, but language is in your frontal cortex so they could not describe what they were doing.

Clearly navigation requires the integration of many inputs.  All the best navigators have a “sense of direction”.  You can ask people if they have a sense of direction and you will get either of two answers:

  • Yes and I rely on it
  • No

This is strange as you would expect a lot of people to say they were not sure, or “perhaps?” but no, it seems to be a binary yes or no.

My friends in the army all say that they are very aware who has a sense of direction as this really is something which can mean life or death.

Clearly people who have a sense of direction know they have.  However, I think that there are unconscious cues being used at the same time.  They are using cues such as the the direction of the sun and the time of day. They use smell where it is useful and they use landmarks too.

Work on homing Pigeons concurs with this.

It is strange that people who have good innate navigational skills in Northern Hemisphere fail utterly in the Southern.

There is a whole lot of interesting research going on for instance:

Kristaps Sokolovskis1,2, Giuseppe Bianco1, Mikkel Willemoes1,2, Diana Solovyeva3, Staffan Bensch1,2and Susanne Åkesson1,4*Have produced a paper, unfortunately based on a tiny sample of three willow warblers (Phylloscopus trochilus yakutensi) migrating from Far East Russia to East Africa.

The researchers looked at various compass mechanisms to describe their routes but none really fitted.  The birds that do these long migrations do not go on straight bearings but go to stop off places to refuel (eat and lay down fat) on the way. No-one knows how they do it.

My conclusion is that classic mechanistic Science is really struggling to answer the questions relating to Animal Navigation.  Please remember that we are animals too.  We need to look further.  But it is true the researchers such Prof Kate Jeffery at UCL London and Benjamin J. Clark of the University of New Mexico and their teams are discovering where navigational skills live in the brain Hippocampus and Retrosplenial-Parietal Network.  All of these are closely linked spatially and in the sub-conscious part of the brain.

We will bring you the latest ideas as they evolve but the cuckoo conundrum still exists. How does a young fledgling cuckoo, whose parents are long gone, set of and find its wintering grounds in the Congo basin?

Richard Nissen

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Animal navigation and biological rhythms: the inertial theory by Antonio B. Nafarrate

Editor’s comments:
This paper is quite old but it does propose another navigation mechanism than the current obsession with magnetic orientation.  The magnetic field  has the terrible drawback of changing all the time and birds have migrating successfully before and after the Earth’s magnetic field flipped South for North.  Albatrosses fitted with head magnets (to see if this ruined their navigation) did not get lost.

The Coriolis acceleration (or force when acting on a mass) can be used to define an inertial bicoordinate map over the surface of the Earth. These coordinates closely correspond to geographic latitude and longitude measured in units of time; in addition the Coriolis force can generate a clock frequency or time base to “calibrate” the biological rhythms.  The elementary detectors are intramolecular rotors or oscillators acting as inertially controlled ion gates forming part of “tunnel” proteins bridging cellular bilayer membranes.  The precessional monitors of these rotors generate the frequencies that encode the space-time coordinates. From an evolutionary standpoint the simplest and earliest application of this inertial model is in a non-statolithic gravity sensing system (detection of the local vertical), followed by sensing of the Earth rotation (timing information) and evolving later into the fully developed bicoordinate navigation system necessary in any animal species capable of migrating or homing.

In spite of the large existing body of knowledge and the large numbers of investigators working in the study of animal navigation or biological rhythms science still has no answers to the fundamental questions on these subjects. Several of the models proposed for animal navigation involve the use of a “clock”, suggesting an interaction between navigation and rhythms; in this model both problems are shown to be essentially connected through the same physical mechanism.

The idea that animals use inertial navigation is not new; among the earlier proponents are Darwin (1), Ising (2), Yeagley (3) and Barlow (4). This model in addition to the concepts used in these earlier models brings a whole new focus to the way that organisms make use of bio-inertial sensors to gain spatio-temporal information.

The inertial theory
An inertial device such as the Foucault pendulum has a particular period of rotation of its plane of oscillation for each latitude; at either pole this period is equal  to the duration of the true sidereal day (23h 56min 4.0996s) and it becomes  infinite at the equator with opposite sense of rotation in the North from the South hemisphere; from these is clear that at least in theory it is possible to measure latitude using a Foucault pendulum, a chronometer and some sort of simple binary rule or cue to decide among North or South hemisphere.

The inertial device that measures longitude does not exist. Because of the geometry problem only changes of longitude can be measured from an arbitrary meridian with the use of a spinning top, a chronometer and again a binary rule or simple cue to decide whether the longitudinal changes are in the East or the West direction. It works as follows: a spinning top anywhere on the Earth, except at either pole, even under ideal conditions will always have some precession because of the contradictory tendencies of falling “asleep”(alignment of the rotational axis with the vertical or local direction of gravity) and the conservation of angular momentum that demands that the axis of rotation should continue pointing to the same direction in space in spite of the rotation of the Earth; as a result a given spinning top will precess with a certain frequency related to the velocity of the motion of the top as it is carried by a rotating Earth (tangential velocity), if in addition the top is transported East or West with some other velocity the precessional frequency will be shifted by the mechanical analog of the well-known Doppler effect of acoustic and optics.

It was shown that a spinning stationary top precesses with a certain frequency because of the Earth rotation, if this frequency is copied by a non-inertial oscillator (neuronal chemical in an organism) the frequency of this oscillator can be used to monitor changes in the inertial oscillator indicating longitudinal displacements; furthermore the frequency in the stationary case identical for both types of oscillators is a suitable “time base” or clock reference frequency useful to time other events of biological interest associated with the Earth rotation. To keep track of the longitudinal displacements only is needed a simple integration of the frequency shifts and it will be shown below that this can be achieved in a surprisingly easy manner.

The comparison of frequencies is usually done by the ”beat” or interference methods ;if an inertial oscillator and a non-inertial one are tuned to the same frequency in the stationary condition and then they are displaced eastwards or westwards at a certain velocity the mechanical Doppler frequency shifts towards lower or higher frequencies respectively experienced by the inertial oscillator will have it beat with the neuronal or chemical non-inertial oscillator, the maxima and minima of amplitude of the beat frequency will happen at nearly equidistant points along any parallel of latitude independent of the velocity of the displacement, counting the beats is equivalent to counting units of distance if simple mathematical linearity is assumed. It is easy to see that this process of velocity integration reduces itself to something similar to counting steps.

After a long history of contradictory reports there is now solid evidence that magnetic fields similar in strength and even weaker than the geomagnetic fields interact with living organisms, the emerging picture is showing two different types of detection one polar and the other axial (5). The polar form can be traced to the chains of magnetite crystal domains (or similar magnetic compounds) described by Blakemore (6), the axial form does not have an accepted explanation at this time, but in the context of the inertial model supplies the strongest evidence of the existency of spinning tops as gravitational-inertial sensor that because of their actual nature (intramolecular rotors or oscillators) are perturbed by magnetic fields.

The following interpretation of the experimental results of Lindauer and Martin (7) with honey bees constitutes a dramatic illustration of the previous statement. Lindauer and Martin measured with incredible patience and accuracy several millions of bee dances and found that the bees were making an error or “missweisung” (actually the bees were never wrong, the error was in the human expectations of what the bees were supposed to do), the human model for the dances predicted the proper result when the beehive was magnetically shielded or the geomagnetic field was compensated by using Helmholtz coils.                                              It will be shown that in the combined influence of the gravitational and geomagnetic field the bees dance as if using an electrically charged spinning top to detect the direction of the vertical and for this reason the “pure” mechanical precession is perturbed by the magnetic Larmor precession. Lindauer and Martin´s summary of results indicate the following:

1-    The magnetic field does not introduce any error when the dance vector direction is along it. The inertial theory claims that this happens because the electromagnetic component of the top is “asleep” along the magnetic field and the Larmor precession is zero and the mechanical precession (gravitational-inertial) shows itself “pure” without error in a full agreement with human expectations (the Karl von Frisch model)

  • The error is largest when the dance vector is perpendicular to the geomagnetic field.

Again the claim of the inertial theory is that the sum of two vectors (the mechanical angular velocities of precession) shows the largest misalignment with the direction of either component just about when the Wiltschko’s (8) model for the magnetic compass of European robins.

Experimental evidence
Over the years a wealth of information pointing to the inertial nature of the navigational system in animal has accumulated but the data that did not fit the “orthodox” school of thinking was easily swept under the rug, and this is in part the reason why Able (9) describes the study of this subject in chaos and turmoil, and indeed it is true because of the lack of comprehensive model to introduce order in a large and ever growing pile of data.

Besides the example already described of the axial form of magnetic detector, the strongest evidence for inertial navigation is the papers that show lunar influences in the orientation and timing of diurnal species (10-12). Within the framework of generally accepted physical science the Moon has only two types of influences over the Earth and its terrestrial inhabitants, one is the inertial-gravitational (mechanical forces; best example: the tides) and the other is electromagnetic, in turn the electromagnetic influence can be divided into optical (direct response to lunar light through the visual system; included here is most of the poetic-romantic influence) and electromagnetic (non-visual). While the electromagnetic lunar influences indeed exist and have been measured they are of an intensity and periodicity such that they add a very small modulation or contribution to solar influences of the same nature and for that reason it is unlikely that lunar rhythms in living organisms are driven or synchronized through electromagnetic cues, on the other hand the situation reverses for mechanical influences where the Moon dominates and the Sun is the lesser contributor. In summary when an organism shows lunar periodicities and visual cues can be ruled out, suspect mechanical effects, if a rhythm has solar frequency components check for electromagnetic effects.

An intriguing hint to the relation between gravity and timing comes from the chemical-hormonal fact that the hormone that mediates the gravitational response of plants, indole acetic acid and the hormone associated with circadian rhythmicity in the pineal gland of vertebrates, melatonin belong to the same chemical family of indoles with serotonin and tryptophan.

There is evidence that animal migration routes are genetically encoded, the just described method of inertial navigation that reduces latitude and longitude to time differences or steps counting lend itself for very simple encoding, the coordinates of a migration path are given by sets of three numbers (date, longitude and latitude) all in time units. Counting in some early cultures was made with the help of beads tied on stings, and today our civilization stores and manipulates information though stings of        data encoded in a variety of physical ways, hence it should not surprise anyone that genetic “stings” can be used as counters. When migrating species expand their range they add new path to their ancestral route as if adding or splicing a new section to their route specification gene.

One of the strongest and earliest opponents to the concept of inertial navigation is Matthews (13) others who follow mainly repeated Matthews’s mistake clearly seen in his book Bird Navigationwhen the Coriolis acceleration is discussed, Matthews’ asserts that the Coriolis acceleration can only provide one coordinate and not a bicoordinate grid necessary for complete map information; curiously enough this inertial model is very similar to Matthews “all solar model” and his concept of astronomical grids. Matthews’ solar model is a daylight version of celestial navigation and it has a profound connection with this form of inertial navigation though a path only recognized early this century by Einstein’s relativity; all the laws of physics have the same form when formulated with respect coordinate axis formed by the axis of telescopes pointing the stars or by the spinning axis of gyroscopes pointing to the same stars, and if this would have been known in the late 1800’s the Michelson and Morley experiment would then have been superfluous, because it would have been recognized that an optical (electromagnetic) experiment could not circumvent the limitations known from Newtonian mechanics that prevent  measuring absolute velocities.

It is to Matthews credit his belief in a simple navigational system and his clear statement that “time is longitude, longitude is time” (13), and this model adds that latitude is also time and both can be defined inertially.

This inertial form of navigation and timing makes use of very basic physical mechanisms available for living organisms at their most early evolutionary stages, and for this reason simple primitive species can amaze us with nearly incredible navigational performances.

Note: A more detailed expanded version of this paper with its additional impact in all areas of biology is under preparation; interested persons are encouraged to contact the author.


  • Darwin, C.R. Origin of certain instincts. Nature, 7, 417-418 (1873). Also Barrett,  H.(ed.). The collected paper of Charles Darwin. The University of Chicago Press. Chicago (1977).
  • Ising, G. Die physikalische  Moeglichkeit  eines tierischen  Orienterungssinnes auf Basis der Endrotation. Ark. Astr. Fys., 32,1-23 (1945).
  • Yeagley, H.L. A preliminary study of physical basis of bird navigation. J.Appl. Phys., 18, 1035-1063 (1947).
  • Barlow, J.S.Inertial navigation as a basis for animal navigation. J. Theor. Biol., 6, 76-117 (1964).
  • Phillips, J.B. Two magnetoreception pathways in a migratory salamander. Science, 233, 765-767 (1986).
  • Blakemore, R. Magnetotactic bacteria. Science, 190, 377-379 (1975).
  • Lindauer, M. and Martin, H. Die Schwereorienterung der Bienen unter dem Einfluss des Erdmagetfeldes. Z. vergel. Physiol., 60, 219-243 (1968).
  • Wiltschko, W. and Wiltschko, R. Magnetic compass of European robins. Science, 176, 62-64 (1972).
  • Able,K.P. Mechanisms of orientation, navigation and homing. In: Gauthreaux, Jr, S.A. (ed.).Animal migration, orientation and navigation, pp. 283-373. Academic Press, New York (1980).
  • Mewaldt, R. and Brown, I. Behavior of sparrows of the genus zonotrichia in orientation cages during the lunar cycle. Z. Tierpsychol.,25,668-700 (1968)
  • Keeton, W.T. and Larkin, T. An apparent lunar rhythm in the day-to-day variations in initial bearings of homing pigeons. In: Schmidt – Koenig, K. and Keeton, W.T. (eds.). Animal Migration, Navigation and Homing. Springer- Verlag, Berlin (1978).
  • Lohmann, K.J. and Willows, A.O.D. Lunar –Modulated geomagnetic orientation by a marine mollusk. Science, 235,331-334 (1987).

13-  Matthews, G.V.T. Bird Navigation, 2ndedn. Cambridge University Press, London ( 1968)

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