'200 Vuu - acy. [ April 



will one day be Forthcoming, will show us thai we have greatly 

 ttted the individual potential accuracy, but on the other 

 hand may it not be possible that in some cases we have under- 

 estimated the case, tor as I above the tirst arrivals of a 

 ies Bight may prove to be always the same birds, bound for a 

 definite latitude and locality. 



Prom Cooke we get the impression that birds cannot in any way 

 predict weather conditions, as has so often been claimed for them, 

 and that such birds as the ducks and geese are much more liable 

 to take advantage of weather conditions, open water, etc., than are 

 the passerine birds. And were this at of the passerines 



correlated in any way with an increased intelligence, wo would 

 tainly expect to see it manifested in birds like the Canada Goose 

 and the ducks, whoso superior mental endowment none can doubt. 

 But here wo seem to see it least, for in the migration oi these inde- 

 pendent fowl there is often an error of weeks as contrasted with 

 - among their more trustful and less intelligent brethren. His 

 not this very intelligence tended in some subtle way to deliver 

 the geese from the bondage, so to speak, of a hide-honnd time sense, 

 ami allowed them a greater scope to grapple with seasonal condi- 

 tions" This has nothing to do with the evolution of the species 

 considered: it simply means specialisation in a given direction. 

 So also it seems to the writer that the 'potential accuracy 

 birds like our Bluebird is probably much greater than we think, 

 but the species is subjected to such a grave variation in season on 

 ant of its early arrival in the north, that it. - S] ak. di>t^ 



merely the best it can. 



her question occurs at this point, which is really not within 

 our enquiry, but may be mentioned, and that is the reason for 

 the liferent migration times of different species. 



I con. is saw in this phenomenon an indication of an orderly 

 depopulation of the North in order to prevent over-population, 

 and he attributed all' that we see now to an equalisation of 

 tribmion through diversity in the time of southern migration. 

 evolved by the pr gress — si I by the require- 



i w w Cook* v. 1910. 



» Auk. IS I vvmi> 



