Avian orientation and navigation.
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Biomedical subjects
Publications and source records attributed to W T Keeton.
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Three series of experiments were conducted to determine whether the orientational and homing behavior of feral pigeons ("Commons") in the U.S.A. is comparable to that of homing pigeons. Wild-caught adult and juvenile Commons showed meaningful nonrandom orientation when released at unfamiliar sites. When such birds were phaseshifted 6 h fast, their vanishing bearings were deflected approximately 90 degrees counterclockwise, thus indicating use of the time-compensated sun compass. Young Commons reared and trained with Homers of the same age differed behaviorally from the Homers in a variety of ways and many fewer returned home from training and test releases, but the season for the fewer returns appeared to be more concerned with social behavior than with orientation capability.
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Magnets glued to the backs of experienced pigeons often resulted in disorientation when the birds were released from distances of 17-31 miles (27-50 km) under total overcast, whereas no such disorientation occurred during similar releases under clear skies. The magnets did, however, often cause disorientation when first-flight birds were released under sun, and there was some indication of disturbance to experienced pigeons released under sun at longer distances.
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Untrained homing pigeons released on sunny days oriented homeward regardless of the direction of the release site from the loft. Similar pigeons released under total overcast vanished randomly, whereas experienced birds released on the same days at the same sites oriented homeward. Apparently untrained pigeons require the sun for orientation but experienced pigeons do not.
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Starvation of larvae of the milliped Narceus annularis results in the formation of a smaller than normal number of body segments in the early stadia. However, this reduced number is compensated for by subsequent formation of a larger than normal number of body segments in the later stadia, or by the addition of extra segment-building stadia. Apparently there is a mechanism whereby the milliped "keeps count" of the number of body segments produced and can regulate the production of these segments from a proliferative region so that the total number of body segments at sexual maturity is within the normal range for the species.
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