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FIG. 1. Tracks of three different homing pigeons, each released repeatedly from three different release sites. For each pigeon, the numbers refer to the chronological sequence of the tracks. Blue WAL from Manchester New Hampshire and Blue YAL from Worcester were returning to a loft in Cambridge, Massachusetts; Blue R19 was returning to a loft in Lincoln, Massachusetts. The total length of the scale bar is 36 km. Notice the variation in successive tracks, especially for Blue R19 from Orange, Massachusetts (From Michener and Walcott, 1967
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FIG. 2. Tracks of pigeons released for the first time off their training line. These tracks from the Worcester, Massachusetts airport show the variability in strategies used by different pigeons when released for the first time at an unfamiliar site. The pigeon that made the track in the top left in the diagram had been trained from Orange, Massachusetts. On its homeward training trip it always passed a prominent mountain, Mt. Wachusett (MTN in the diagram). Notice how, on its first release from Worcester, it seemed to head for the mountain before flying home
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FIG. 3. Pigeons wearing head coils were radio tracked from Carver, Massachusetts 74 km South of the loft under sunny skies. Two coils were generating an earth strength magnetic field around the pigeon's head, differing only in their polarity. NUP coils, placed around a magnetic compass, caused the north-seeking needle of the compass to point toward the bird's head coil (top line), SUP coils (X lower line) had the opposite polarity. The third line (O lower curve) represents birds carrying both coils and batteries but with no current flowing. Each point represents the average direction of each group of birds during the first 15 minutes after release. The left vertical scale is the pigeon's bearing relative to magnetic North; the right scale is the bearing relative to home. Notice how the substantial difference in bearings between the NUPs on the one hand and the SUPs and no current birds on the other at 4 minutes after release gradually decreased to a small difference at 15 minutes when most birds vanished from radio range (From Walcott, 1977)
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FIG. 4. The mean vanishing bearings of Cornell pigeons released at Castor Hill Fire Tower, 160 km NNE of the loft in Ithaca, New York, over a 19 year period are plotted year by year. The upper line is for birds that had never been released at Castor Hill before; the lower line is for pigeons that have been released at the site before. The remarkable variability in the release site bias seems to have several cycles over a period of years. Experienced birds typically show less deflection than those new to site but the peak years of their deflection seems lag that for birds new to site. The deflection at Castor Hill is always clockwise from the home direction (indicated by 0°). Each point is the mean vanishing bearing of 3 to 6 different pigeons
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FIG. 5. The vanishing bearings of 984 pigeons released at Jersey Hill Fire Tower located just West of Hornell, New York, 137 km W of Ithaca. Each dot represents the vanishing bearing of an individual pigeon released under sunny skies over a 14 year period. The dashed line indicates the direction to home; the length of the mean vector of all the vanishing directions is 0.0065 at 160 degrees. Because of the huge number of releases, this direction is significantly different from random (Raleigh Test) at P = 0.04. Less than 10% of these pigeons ever returned to the home loft (From Walcott and Brown, 1989)
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FIG. 6. The Jersey Hill vanishing bearings of young birds raised in the Cornell loft in Ithaca, New York 135 km to the East of Jersey Hill and those of young birds raised in the Reenstra loft 396 km Southeast of Jersey Hill. Both lofts contained young birds from Cornell stock and from New Jersey stock. Both groups received identical training before release. Young birds of whatever stock raised in New Jersey were well oriented and a total of 4 out of 23 birds returned home the day of release. Birds of both stocks raised at Cornell were disoriented and only 1 out of 24 pigeons returned home the same day (From Walcott and Brown, 1989)
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FIG. 7. Pigeons living in the loft at Fox Ridge Farm in Lincoln, Massachusetts were released at a variety of different strength magnetic anomalies. The consistency of the pigeon's vanishing direction at each anomaly, as measured by the length of the mean vector, is plotted against the variability in the magnetic field over a distance of 1 km in the home direction. Plotting the logarithm of vector length against the logarithm of the magnetic variability results in a straight line relationship (r = 0.91) with greater magnetic variability associated with poor orientation (From Walcott, 1980)
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FIG. 8. The relative vanishing bearings of pigeons raised in two lofts in Lincoln, Massachusetts separated by about 2.5 km. The Fox Ridge Farm loft and the Codman Farm loft were stocked with siblings and both groups of birds were trained together. At most release sites the behavior of the two groups of birds was identical. At the magnetic anomaly at Iron Mine Hill, near Woonsocket, Rhode Island, the Codman Farm pigeons were well oriented while the Fox Ridge Farm pigeons were disoriented (From Walcott, 1992)
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FIG. 9. A portion of the aeromagnetic map of Lincoln, Massachusetts showing the position of the pigeon loft at Codman Farm (left hand dot) and that at Fox Ridge Farm (right square). In this map, lines of equal magnetic intensity are shown but the normal, background earth's magnetic field in removed. The map shows that the loft at Fox Ridge Farm is located on a steep magnetic gradient of 450 nT/km whereas the Codman Farm loft is located in a more uniform magnetic field with a gradient of only 80 nT/km. From Walcott (1992)
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