1913 ' J Phillips, Migration and Periodic Accuracy. 20. > 



We have, it musl be said, various other periodic reflexes, depend- 

 ent on feeding habits, the diurnal movement of lower organisms 

 following the light, and the tidal movements of various littoral 

 creatures, with very likely a host of other-. But none of the <■ o 

 far as I am aware exactly fits our case in bird . In fish, it is true, 

 e pecially in the salmon family, we see an accurate periodic move- 

 ment, often begun month- b< fore the -j>au ning time, and therefore 

 hardly carried out alone by a direct stimulus from developing eggs 

 or milt. Ocean fish, like the herring of Europe, how character- 

 istic spawning times and spawning places for each closely related 

 race. Hats and fur-seal- among mammals are other examples 

 hut as to the accuracy of arrival of these animal 1 am not informed. 



I think it is plain, then, that the migratory impulse in birds is 

 not to he explained on the basis of a purely physico-chemical 

 response to an internal secretion, at least not that phase of it. which 

 pertains to potential accuracy. This may he a part hut not the 

 whole story. Nor does one wi-.li to drag in ^>y the heel-, any ques- 

 tion of intelligent effort, for this would not help us in the least, 

 and would tend to diminish rather than increase tin- time sense. 

 I say diminish because instinct appears so much more mechanical, 

 regular and Mind than intelligence ever doe . 



If one accepl 3 Darwinism in so far as it applies to the selective 

 value of useful variations, it seems hard to see how this chro- 

 nometer-like accuracy can have been evolved; or even assuming it 

 to have arisen through an adaptive necessity, it is still harder to 

 See why it should remain in it- present perfection, for tin; most 

 enthusiastic Darwinian could scarcely picture it a-, a matter of 

 great moment to the species if it arrived one week early or one 

 week late, with the whole -ca-on hefore it. We must grant of 

 course one great source of error in our conception of potential 

 accuracy, for as stated above, we are forced to deal with groups 

 in tead of individuals; still with a long series of years it seems as if 

 one miidit gain a pretty correcl impression of the accuracy of the 

 individual bird i' -elf. 



The writer is familial- only in a general way with the subject at 

 hand, and has merely attempted to call attention to an aspect of 

 migration which does not seem to have been much discussed. 

 Whether it i- even worth discussing in the li-ht of our -cant knowl- 



