20 HOMING AND RELATED ACTIVITIES OF BIRDS. 



REFLEX THEORIES. 

 REFLEX THEORIES BASED ON THE FUNCTIONING OF SEMICIRCULAR CANALS. 



Reynaud,* although having at his command the best facilities for making 

 scientific observations, has contributed little on the factual side to the study 

 of homing. For some years he had charge of the movable cotes of the French 

 army, and later of the carrier-pigeon post of "La Compagnie Transatlan- 

 tique." His theoretical views have been cry.stallized into a "loi du contre- 

 pied." This law merely states that the pigeon returns by the route over which 

 it was carried, retracing, on return, all of the windings of the forward trip. He 

 tries to get some factual support for this law by keeping a record of the finding 

 of lost birds. The birds at times disappear and are usually found, according 

 to him, at some point on the route over which they have been carried. His 

 records, however, are extremely sporadic and are of no scientific value. He 

 assumes, furthermore, that there is proof for his theory in the great migration 

 routes of birds and in those of fishes. He maintains that both the forward 

 and the return migration routes are the same in every case, and that certain 

 species of both birds and fishes have practically been exterminated Ijy sports- 

 men because of their adherence to these routes. That such is not often the case 

 has been quite clearly shown by Cooke, who proves very plainly that in many 

 cases Northern and Southern migrations do not take place along the same route. 

 The most notable examijle of this is to be found in the plover (see p. 29). 



Like a good many others, Reynaud places the mechanism of return in the 

 semicircular canals. The stimuli to it, although not clearly defined by him, 

 are practically the same as those of Bonnier. The twists and turns which the 

 bird receives as it passes over the forward route are stored up in some way so 

 that they become effective as stimulators when the liird returns (see Bonnier's 

 attitude theory). 



A crucial test of Reynaud's theory could easily have been devised by him 

 by taking the bii'd along an extremely circuitous route anil tlien releasing him, 

 e. g., not more than 300 miles from his home. If the bird returned at the end 

 of 5 to 6 hours, we may be sure that it returned by the direct route. If, on the 

 other hand, several days were consumed, we might have some grounds for 

 supposing that the longer route was chosen. He maintains that he has made 

 such tests, but no satisfactory publication of them has ever been made. (See 

 reference to other articles by Reynaud, in C'laparede's bibliograjihy.) 



Bonnierf advances a theoiy (no experiments given) which may be classed, 

 despite its appeal to memory, as a reflex theoiy. It was put forth after the 

 contrejjied theory of Reynaud and does not differ from it except in attempting 

 to account for direct returns (that is, for known cases where the bird does not 

 retrace the various stages of the forward joiu-ney, but on the retiu'n takes a 

 direct route). According to Bonnier there are two general methods of orien- 

 tation. One is able to orient oneself on the moment of arrival or at the instant 

 of departure. In order to orient in advance, or at the moment of release, 

 landmarks (reperes) of one kind or another are necessary. But in many cases 

 the conditions are made such that landmarks are not at hand. Hence, 

 Bonnier believes that orientation is always obtained by refei-ence to the point 



*Bird Lore, 2, pp. 101-108; ibid., pp. 141-147. 

 tBoimier, P.: L'Orieut.ition, Scientia, No. 9, 1900. 



