The Effect of Magnetic Anomalies on the Homing Behaviour of Pigeons: An Attempt to Analyse the Possible Factors Involved

Kiepenheuer, J.

doi:10.1007/978-3-642-68616-0_12

Cited by 35 publications

(17 citation statements)

References 15 publications

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“…Thus the anomaly sites nos. 31, 34, 38, 41, 42, 44, 48, and 63 are of the same order as those within the Kaiserstuhl anomaly tested by Kiepenheuer (1982) (since I read AT's ranging from approximately -150 to 450 nT from the aeromagnetic map the author presented). Potentially, the anomalies in New England (USA) tested by Walcott (1978) are stronger still (up to 3000 nT near the ground).…”

Section: Relations To Magnetismmentioning

confidence: 62%

“…The latter varied widely with respect to departure from the normal field, gradient, extent, direction, and distance from home . At the strongest anomalies tested the magnetic field departed from normal a maximum of -250 and 300 nT at 600 m above the ground with gradients up to 376 nT per km; hence, the anomalousness was of the same order as in the Kaiserstuhl anomaly tested by Kiepenheuer (1982).…”

Section: Methodsmentioning

confidence: 71%

“…While the normal field strength grows very slightly with falling altitude, AT does so dramatically according to an exponential function; it increases the greater AT and the depth of the magnetic mass are beneath the earth's surface (see Kiepenheuer 1982). Using this function together with the depth estimates, I calculated the amplitudes at the stronger anomalies (AT_> 68 nT) at the pigeon's flight level and replaced AT at 600 m above ground (first value) by AT at 50 m above ground (second value) as follows (nT): no.…”

Section: Independent Variablesmentioning

confidence: 99%

“…Another possibility is that pigeons released within various anomalies switch to an alternate cue system. Although their orientation improved when they were released for a second time at the same anomaly (Kiepenheuer 1982), experience at magnetic anomalies in general did not improve the homeward orientation at a specific unfamiliar anomaly (Lednor and Walcott 1988). Thus, greater experience with anomalies may be not a likely cause for the good orientation of my pigeins over magnetic anomalies.…”

Section: Relations To Magnetismmentioning

confidence: 99%

“…This question was studied by testing the homing behavior of pigeons released at magnetically abnormal sites: The pigeons vanished with deviations from the homeward direction at moderate magnetic anomalies in Switzerland (Frei and Wagner 1976;Wagner 1976;Frei 1982) and failed to orient towards home at very intense magnetic anomalies tested in the USA (Walcott 1978;Lednor and Walcott 1988) and in the FRG (Kiepenheuer 1982(Kiepenheuer , 1986. Thus, orientational deficits seem to be slight at less intense magnetic anomalies but serious at very intense ones.…”

Section: Introductionmentioning

confidence: 99%

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Pigeon homing in relation to geomagnetic, gravitational, topographical, and meteorological conditions

Dornfeldt

1991

Behav Ecol Sociobiol

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Experienced homing pigeons were released at sites unfamiliar to them and with magnetic and gravity anomalies as well as in areas with rather normal fields throughout the FRG (41 releases when sunny, 14 when overcast; Figs. 1-3). The second-order release data were subjected to both univariate and multivariate statistical analysis (stepwise regression, factor analysis). The magnetic field strength and its gradients within the l-km circle around the release site were determined from aeromagnetic maps of the anomalies of magnetic total intensity. Analogous variables were derived from gravity anomaly maps. It was tested whether the pigeons fly along that gradient to minimize the difference between the magnetic or gravity field at the release site and the loft at maximum rate. Further independent variables described magnetic K index, day-to-day variations of the magnetic components, topography, meteorological conditions, the number of the releases the pigeons had done, and the distance.Over magnetic anomalies widely varying in strength (departing -250 nT to 300 nT from normal 600 m above ground), extent, and distance from loft, the pigeons vanished with less deviation from the homeward direction and faster than they did in areas with less irregular fields under sunny conditions; this is in contrast to other studies on magnetic anomalies, except one. At sites of gravity anomalies (15M9 regal), the pigeons were significantly less homeward oriented and homed slower than at less anomalous sites (-9 to 14 mgal).Variables related to gravity were best predictors in 8 and and second predictors in 3 out of 15 regression analyses of the navigational parameters for the releases under sun. Six times the (absolute) amount of the gravity difference between the release site and the loft was selected first (Figs. 7 B, C, 8 B, C). The results suggest gravity to be involved in navigation as the pigeons' distance measure. Homeward directedness declined with increasing amount of the gravity gradient in the first 12 releases under sunny skies as well as when overcast (Fig. 8A). A preferred compass direction towards north-northeast was determined, being closest to the grand mean vector of the ascending gravity gradient (Fig. 6). The analyses failed to show directional preferences as assumed by the hypotheses tested. Temperature and degree of cloud cover provided some information for predicting mean vector lengths and mean vanishing times, respectively. The surface wind component in the homeward direction was correlated with median homing performances.

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Section: Relations To Magnetismmentioning

confidence: 62%

Section: Methodsmentioning

confidence: 71%

Section: Independent Variablesmentioning

confidence: 99%

Section: Relations To Magnetismmentioning

confidence: 99%