IVORY TOWERS / One fluke over the pigeon's nest

DO SUCCESSFUL homing pigeons have a better sense of direction than unsuccessful homing pigeons? Hans G Wallraff of the Max-Planck-Institut fur Verhaltenphysiologie in Germany has been conducting some experiments and his results are published in Animal Behaviour (vol 47, 1994, 833-846). His conclusion is that the also- flews in the pigeon-homing stakes suffer not so much from lack of talent as bad luck or poor motivation.

Until the late 1980s, pigeons had been thought to navigate by a combination of astronomical, magnetic and visual environmental clues. Then a series of research papers began to appear which shifted attention to the sense of smell. 'Meteorologisch Gesichtspunkte zur olfaktorischen Navigationshypothese' (Becker and Raden, 1986), 'The orientation behaviour of anosmic pigeons in Frankfurt' (Wiltschko, Wiltschko and Jahnel, 1987), and 'Intra-nasal zinc sulphate irrigation in pigeons: effects on olfactory capabilities and homing' (Schlund, 1992) give a whiff of the new direction in homing theories. 'It became increasingly obvious,' writes Dr Wallraff, 'that pigeons, Columba livia, extract positional information from atmospheric trace gases received by olfaction.'

He describes this finding as 'intuitively unbelievable', but finds the evidence too strong to ignore. If correct, it could explain the great variability in homing performances of individual pigeons: sniffing rare gases is an unreliable information source. So he re-examined three years of pigeon-homing data, over distances from 30 to 180km, to see what role luck played in a pigeon's performance.

'Many pigeons fail to return from their first release,' he points out, and asks: 'Were the lost pigeons habitual failures or were they sorted out by chance?' Here we have a methodological problem: 'The question cannot be answered . . . because these pigeons are no longer available for inter-individual comparisons. One can, however, ask whether those birds that failed to home from the second release performed poorly in some way during the first flight.'

The data show 'no indication that pigeons lost after the second release might have been particularly slow in returning from the first release'. He says: 'A predisposition of individual pigeons to get lost during the next few flights cannot be predicted on the basis of particularly slow homing from the first releases.' He concludes that individual differences in navigational ability count for very little in homing performance. 'As in a game of dice, it is a matter of chance whether a given bird is 'lucky' or 'unlucky' in having nade a good directional choice.' Only highly motivated birds, however, will have the persistence to find their way home if they set off in the wrong direction.

Pigeon racing is a different matter, where the direction is usually the same and the contest is primarily one of speed. Where pigeons are released at an unfamiliar site, however, punters might as well ignore the form book.