HISTORICAL AND EXPERIMENTAL STUDY OF HOMING. 15 



In accordance with this theory Hodge finds as follows : 



Of a large number of birds sent away by rail for longer flights, not one made the return 

 trip in less time than would have enabled him to fly on the involute of a circle from the place 

 of Uberation. This refers to "first flights." The best time made was 26 miles in 5 hours 

 and 9 minutes. Three other birds hberated at the same time failed to return. Letting 

 the distance to which a prominent landmark is visible be 3 miles, a fair estimate for pigeons 

 with some training and over broken country, the least length of an involute of a circle 

 which would bring a bird from a distance of 26 miles to within sight of the loft is 219 miles. 

 In 5 hours it is not likely that the pigeon flew less than 2.50 miles. 



Duchatel* advances the highly speculative view that the retina of the bird 

 is sensitive to infra-luminous rays, especially infra-red, the waves of which 

 are supposed by him to follow the surface of the earth, and consequently are 

 not interrupted by its sphericity. In answer to this speculation we are now 

 in the position to state that the retina of the homing pigeon is no more sensi- 

 tive to these rays than is the retina of the human being. It was to meet 

 Duchatel's supposition that we undertook the work on spectrum sensibility 

 in birds, the result of which is shown on pages 87 to 104 inclusive. 



EXPERIMENTS SHOWING IMPORTANCE OF VISUAL IMPULSES IN HOMING. 

 It is generally agreed that pigeons home with difficulty in cloudy weather. 

 Rodenbachf released 6 good pigeons at 10 a. m., 30 km. from their cote. The 

 sun was obscured by clouds. None of the birds returned the same day. Two 

 returned the second day after the clouds had partly disappeared ; two on the 

 thu'd; and two failed to return. Furthermore, Hachet-SoupletJ shows that 

 they do not home at all at night. He released pigeons at different hours of 

 the day as follows: 



No. 1 at 8 a. m., returned at S"" 2.5'". 



No. 2 at 10 a. m., returned at 10'' 20". 



No. 3 at 12 m., returned at 12'' 20°°. 



No. 4 at 4 p. m., returned at 4'" .30"°. 



No. 5 at 8 p. m., returned at 4'' 15" the following morning. 



No. 6 at midnight, returned at 5'* 5° the following morning. 



From this Hachet-Souplet draws the conclusion that the birds are guided 

 back to their nests by an "attraction visuelle." He neglects to take into ac- 

 count the records we have upon birds which migrate at night. 



Rodenbach also made a test on a blind pigeon. After recovery the pigeon 

 was placed before the entrance to its cote. Guided by the voices of its compan- 

 ions it was able to enter the cote and to beat its way to the right or left. On 

 the following day it executed this feat more easily. On the third day it was 

 taken some distance from its cote. Again, guided by hearing, it joined its com- 

 panions on the roof. With great difficulty and by making desperate efforts it 

 was able at the end of 2 days to reenter the cote. Some days later the bird was 

 released in an open field at a distance from its cote which a sound bird could 

 cover in 10 minutes. The blind bird flew vertically upward without circling, 

 then to the south in a direction opposite to its cote. The bird never returned. 

 These results agree with those obtained by Hachet-Souplet upon good fliers 

 which had become blind. These birds, when released within 4 leagues of their 

 cote, flew away and did not return. 



*Ann. de psych, zool., i. 1901, p. 22; ii, 1902, p. 48. 

 tRodenbach. Zeitsch. f. Brieftaubenkunde, 1895, p. 1.34. 

 tHachet-Souplet. AnnaU de psych.-zool., ii, pp. 3.3-60. 



