Orientation in birds. The sun compass.

The sun compass was discovered by G. Kramer in caged birds showing migratory restlessness. Subsequent experiments with caged birds employing directional training and clock shifts, carried out by Hoffman and Schmidt-Koenig, showed that the sun azimuth is used, and the sun altitude ignored. In the laboratory, McDonald found the accuracy to be +/- 3 degrees(-)+/- 5 degrees. According to Hoffmann and Schmidt-Koenig, caged birds trained at medium northern latitudes were able to allow for the sun's apparent movement north of the arctic circle, but not in equatorial and trans-equatorial latitudes. In homing experiments, and employing clock shifts, Schmidt-Koenig demonstrated that the sun compass is used by homing pigeons during initial orientation. This finding is the principal evidence for the existence of a map-and-compass navigational system. Pigeons living in equatorial latitudes utilize the sun compass even under the extreme solar conditions of equinox, achieving angular resolution of about 3 degrees in homing experiments. According to preliminary analyses, the homing pigeons' ephemerides are retarded by several weeks (Ranvaud, Schmidt-Koenig, Ganzhorn et al.).

Seasonal variation in the orientation of homing pigeons: new evidence for a latency in the sun compass.

Homing pigeons must keep track of the seasonal variations in the sun's daily motion to use the sun as a reference. A delay of seven weeks in such updating of their ephemerides was previously interpreted as being the cause of the behavior of control pigeons studied near the equator in September, when birds released in the morning flew anomalously to the right of birds released in the afternoon. Demonstration of the chronic existence of a delay was obtained by observing that the anomaly was still present but inverted in sign in March, when the pigeons released in the morning flew to the left of those released in the afternoon.

Seasonal variation in the orientation of homing pigeons: new evidence for a latency in the sun compass

Homing pigeons must keep track of the seasonal variations in the sun's daily motion to use the sun as a reference. A delay of seven weeks in such updating of their ephemerides was previously interpreted as being the cause of the behavior of control pigeons studied near the equator in September, when birds released in the morning flew anomalously to the right of birds released in the afternoon. Demonstration of the chronic existence of a delay was obtained by observing that the anomaly was still present but inverted in sign in March, when the pigeons released in the morning flew to the left of those released in the afternoon

Directions of migrating monarch butterflies (Danaus Plexippus; Danaidae; Lepidoptera) in some parts of the eastern United States.

In September 1977, the directions of 477 migrating monarch butterflies were recorded at five locations in the Eastern United States. The monarchs moved highly directed generally to the southwest, roughly in accordance with the orthodrome direction, to their assumed winter quarter in Mexico. Deviations from the precise direction seemed to be due at least partly to wind drift; major drift required navigational compensation.

Homing in pigeons with impaired vision.

In order to test the importance of vision in homing pigeons, their vision was impaired by frosted contact lenses. Pigeons wearing such lenses seemed unable to recognize artificial landmarks at 6-m distance. Nevertheless, most birds homed from distances of 15 km, and some even from 130-km distance. This result indicates that, contrary to common expectation, vision need not play an essential role in homing.