Magnetic Navigation by an Avian Migrant?

217

214

SUMMARY Diverse animals detect the Earth's magnetic field and use it as a cue in orientation and navigation. Most research on magnetoreception has focused on the directional or `compass' information that can be extracted from the Earth's field. Because the field varies predictably across the surface of the globe, however, it also provides a potential source of positional or `map'information, which some animals use to steer themselves along migratory pathways or to navigate toward specific target areas. The use of magnetic positional information has been demonstrated in several diverse animals including sea turtles, spiny lobsters, newts and birds, suggesting that such systems are phylogenetically widespread and can function over a wide range of spatial scales. These `magnetic maps' have not yet been fully characterized. They may be organized in several fundamentally different ways, some of which bear little resemblance to human maps, and they may also be used in conjunction with unconventional navigational strategies.

Section: Magnetic Maps and Target Areasmentioning

confidence: 85%

Magnetic maps in animals: nature's GPS

Lohmann

Putman

2007

217

214

“…Åkesson and Alerstam, 1998) but apart from that there are few studies dealing with potential coordinates of a map. According to the review by Freake et al (Freake et al, 2006), there is only one direct test of the use of magnetic cues to determine latitude in migratory birds: a study of Australian silvereyes (Fisher et al, 2003) showed northward orientation (towards wintering grounds) when the birds were exposed to a field with magnetic inclination and intensity corresponding to a location south of the winter range but when the birds where exposed to magnetic conditions corresponding to those on the wintering grounds the birds were not significantly oriented. However, as with the experiments on newts, turtles and lobsters, the interpretation of the results is still not clear.…”

Section: Navigation and Bi-coordinate Maps In Migrating Animalsmentioning

confidence: 99%

The bird GPS – long-range navigation in migrants

Thorup

Holland

2009

SummaryNowadays few people consider finding their way in unfamiliar areas a problem as a GPS (Global Positioning System) combined with some simple map software can easily tell you how to get from A to B. Although this opportunity has only become available during the last decade, recent experiments show that long-distance migrating animals had already solved this problem. Even after displacement over thousands of kilometres to previously unknown areas, experienced but not first time migrant birds quickly adjust their course toward their destination, proving the existence of an experience-based GPS in these birds. Determining latitude is a relatively simple task, even for humans, whereas longitude poses much larger problems. Birds and other animals however have found a way to achieve this, although we do not yet know how. Possible ways of determining longitude includes using celestial cues in combination with an internal clock, geomagnetic cues such as magnetic intensity or perhaps even olfactory cues. Presently, there is not enough evidence to rule out any of these, and years of studying birds in a laboratory setting have yielded partly contradictory results. We suggest that a concerted effort, where the study of animals in a natural setting goes hand-in-hand with lab-based study, may be necessary to fully understand the mechanism underlying the long-distance navigation system of birds. As such, researchers must remain receptive to alternative interpretations and bear in mind that animal navigation may not necessarily be similar to the human system, and that we know from many years of investigation of long-distance navigation in birds that at least some birds do have a GPS -but we are uncertain how it works.

“…The intensity and/or inclination of the Earth's magnetic field could be used to determine latitude (Phillips, 1996), and it has also been argued that the difference between magnetic (Phillips et al, 2006). In migratory birds, the results of a simulated magnetic displacement experiment suggest that magnetic cues may play a role in the determination of latitude (Fischer et al, 2003). A second line of evidence that magnetic cues play a role in migratory navigation comes from treatments involving strong, brief magnetic pulses.…”

Section: Introductionmentioning

confidence: 99%

Testing the role of sensory systems in the migratory heading of a songbird

Holland

Thorup

Gagliardo

et al. 2009

104

SUMMARYThe identification of the sensory cues and mechanisms by which migratory birds are able to reach the same breeding and wintering grounds year after year has eluded biologists despite more than 50 years of intensive study. While a number of environmental cues have been proposed to play a role in the navigation of birds, arguments still persist about which cues are essential for the experience based navigation shown by adult migrants. To date, few studies have tested the sensory basis of navigational cues used during actual migration in the wild: mainly laboratory based studies or homing during the non-migratory season have been used to investigate this behaviour. Here we tested the role of olfactory and magnetic cues in the migration of the catbird (Dumetella carolinensis) by radio tracking the migration of birds with sensory manipulations during their actual migratory flights. Our data suggest that adult birds treated with zinc sulphate to produce anosmia were unable to show the same orientation as control adults, and instead reverted to a direction similar to that shown by juveniles making their first migration. The magnetic manipulation had no effect on the orientation of either adults or juveniles. These results allow us to propose that the olfactory sense may play a role in experience based migration in adult catbirds. While the olfactory sense has been shown to play a role in the homing of pigeons and other birds, this is the first time it has been implicated in migratory orientation. Supplementary material available online at