Pigeon homing: the effect of a clock-shift is often smaller than predicted

Abstract

Pigeon homing: the effect of a clock-shift is often smaller than predictedAbstraet This analysis is based on 103 releases with 6-h clock-shifted pigeons of various ages and experiences. Resetting the internal clock normally leads to a significant change in initial orientation; however, in half of the cases, the induced deflections are significantly smaller than predicted by the sun compass hypothesis. The relative size of the deflections decreases with increasing age and experience (Fig. 3). Only young pigeons with limited experience respond as expected, while old birds show deflections which are, on the average, only slightly more than half of the predicted size, except at extremely familiar sites (Table 2). There is no difference between fast and slow shifts (Fig. 4). It is not possible to clearly specify under what circumstances smaller deflections occur; previous clock-shifts (Fig. 5), familiarity with the release site ( Table 4) and duration of the shifting procedure (Table 5) do not seem to be the reasons. Clock-shifting also tends to decrease the vector lengths and has a marked effect on homing performance (Table 7). Nevertheless, considerable numbers of clock-shifted birds return on the day of release before their internal clock has begun to be reset back to normal. The general role of the sun compass in bird orientation is considered and theoretical implications of our findings are discussed in view of the 'map and compass'-model and the possibility that an alternative, non-time-compensating compass is used in parallel with the sun compass.

The effect of clock-shift on the initial orientation of wild rock doves (Columba l. livia)

“…Although the results revealed an evident effect of the fast-shift, comparable to that observed in homing pigeons (see Wiltschko et al 1994;Chappell 1997;Wallraff et al 1999;Wiltschko and Wiltschko 2001), shifted doves, but not controls, tended to orient homeward. These results suggested a possible influence of the release time per se on the orientation of the tested doves; namely, shifted birds, released in their subjective afternoon, might have been motivated to reach home, while controls, released in the morning, might have been induced to fly away from the release site in search of food, as suggested by Baldaccini et al (2001).…”

“…For logistic reasons, AC and MC were not subjected to an artificial photoperiod, but were confined to a similar sized loft exposed to natural daylight. This control treatment has been used on homing pigeons (see, e.g., Wiltschko et al 1994) and apparently does not interfere significantly with the outcome of the experiments. The mean deflection expected from the treatment, calculated as in Wiltschko et al (1994), was 92.…”

“…This control treatment has been used on homing pigeons (see, e.g., Wiltschko et al 1994) and apparently does not interfere significantly with the outcome of the experiments. The mean deflection expected from the treatment, calculated as in Wiltschko et al (1994), was 92. Birds were transported in well-ventilated baskets to the release site [site C in Baldaccini et al (2001); home direction = 275; home distance = 18 km], which was within the foraging flight range of the population in question (Baldaccini et al 2000).…”

Pigeons combine compass and landmark guidance in familiar route navigation

“…3A, the birds showing the highest track inconsistencies (e.g., tracks 1-4) appeared to respond to clock-shift in the conventional way, albeit with reduced deflection. However, many birds, particularly those with small intertrack inconsistencies, flew routes or segments thereof having the form of their established routes, but in parallel (e.g., tracks [11][12][13][14][15][16][17][18]. This parallel route recapitulation is accompanied by a distinct anticlockwise offset.…”

“…Birds displaced off route usually return directly to their memorized path, implicating direct attraction to visual landmarks (10). Nevertheless, clock-shift experiments, which attempt to alter the pigeon's dominant time-compensated suncompass, indicate that compass orientation may be used even from familiar release sites (8,(11)(12)(13)(14)(15)(16)(17)(18)(19). Thus the role of the sun-compass remains substantially unresolved, with inferences largely dependent on classical vanishing data which can only provide partial information on a bird's navigational decisions.…”