Vol j^ XII "l Kopman, Warbler Migration in La. and Miss. 2QI 



The second point, and it is a matter upon which much differ- 

 ence of opinion might readily exist, concerns Professor Cooke's 

 method of finding the average date of first arrival in spring. To 

 add the number of days intervening each year between the first 

 of the month in which the earliest record falls and the day of 

 arrival for the year in question, and then to divide by the number 

 of records, may be the best method to find the average date of 

 arrival where the seasons are very consistent and regular ; but in 

 a region where there is occasionally a peculiarly abnormal year, 

 the use of the record for such years vitiates the determination of 

 the normal or typical time of arrival. Again, this is a matter that 

 can be settled for any one region only by those who are on the 

 ground all the time, and can use judgment in selection. The 

 very late dates occasioned by late blizzards have been used by 

 Professor Cooke in finding the average dates of arrival for this 

 latitude. The records themselves do not in every case reflect the 

 true state of affairs for certain seasons, because opportunities for 

 observation in some of such years were limited, and the best date 

 obtained was sent, though it might be known to be a late date. 

 The necessary notes to that effect, it is true, were not appended 

 in all cases. These circumstances aside, however, in this latitude 

 at least, the average date of arrival in spring is the average of all 

 records for normal seasons, though this statement applies better 

 of course to the early part of the season, since a season rapidly 

 catches up time once it has a good headway. It should be added 

 that it would be as much of a mistake to include the date of 

 arrival for one of our extremely forward springs as the date in 

 a spring delayed by a blizzard. Including both extremes, one 

 might expect to come reasonably near the practical rather than 

 the ideal average, but in one case at least, that of the Hooded 

 Warbler, Professor Cooke's method carries us considerably astray. 

 The date upon which the Hooded Warbler appears most likely to 

 arrive in a normal season is March 12. Professor Cooke, how- 

 ever, using the records available to him, determines the average 

 date of arrival at New Orleans to be March 25. If one had a 

 very full and trustworthy record, would not the best method, after 

 all, be to settle upon that date which occurs most frequently ? In 

 the case of many species there would certainly be such a date. 



