ORNITHOLOGIST 



— AND — 



OOLOGIST. 



SI.OO per , 

 Annum. 



FRANK B. WEBSTER, Publisher. 

 Established, March, 1875. 



Single Copy 

 10 Cents. 



VOL. IX. 



PAWTUCKET, R. I., DECEMBER, li 



No. 12. 



Migration in the Mississippi Valley. 



SPEED OF MIGRA TIOX. 



"When we come to study the speed at 

 which the birds proceed northward in their 

 migrations, Ave are beset by many difficul- 

 ties. To determine the comparative speed 

 of the several species is easy enough, now 

 that we have the requisite data in hand, 

 but to determine the absolute rate, the 

 definite number of miles which a given 

 species makes during one day's journey, 

 this is beyond our power, and from the 

 nature of the case, so it will ever remain. 

 If migration were a stead}' movement 

 northward, with the same individuals al- 

 ways in the van, we might by careful ob- 

 servation, arrive at an approximation. In- 

 stead of this, the movement in migration 

 somewhat resembles that of a game of leap- 

 frog. In the fall migration the younger 

 birds lead, but in the spring they loiter far 

 behind, and it is the old birds, those in 

 whom we may suppose the love of home 

 and the desire for procreation are strongest, 

 that press forward so largely. Moreover, 

 of these old birds those which arrive first 

 at a given place are as a rule, birds which 

 lived there the previous summer and which 

 will remain there to breed. Thus the van 

 guard is constantly arresting itself and the 

 forward movement must wait the arrival 

 of the next corps, which may be near at 

 hand or far behind. The movement of 

 migration then, is a constant series of over- 

 lappings and the real speed is evidently 

 much more than the apparent. Of this 

 real speed of transit, we can take no ac- 

 count, and our ' calculated rates therefore 



are of value only in showing the relative 

 speed of migration of the different species. 

 For our purposes the speed of migration 

 is calculated as follows : the most southern 

 reliable record is selected to be compared 

 with the most northern record which can 

 be relied upon ; the distance in miles be- 

 tween these two stations is divided by the 

 number of days elapsing from the time the 

 bird made its appearance at the southern 

 station, to the date at which it was seen 

 by the northern observer ; the result being 

 the average rate of migration in miles per 

 day. To take a concrete example: The 

 Baltimore Oriole (I. galbula,) was seen at 

 Eodney, Miss., lat. 31 52 , on April 7th. It 

 was not seen at Oak Point, Manitoba, lat. 

 50 30 , until May 25th. It was therefore 

 forty-eight days in passing over the twelve 

 hundred and ninety-eight miles between 

 the two stations, or an average rate of 

 twenty seven miles a day. We will treat 

 the subject as thoroughly as possible, since 

 it has received little or no attention ; in- 

 deed there were no data in existence for 

 its study until the notes were collected 

 last year. 



The first records ever published on the 

 subject in this country, are notes on six 

 species which appeared in the O. and O., 

 for January, 1884, pp. 1 and 2. These 

 records were based on the observations 

 sent in for the spring of 1883, and though 

 the notes for 1884, are many fold more nu 

 merous, they do not give us grounds for a 

 change in the general laws of speed as set 

 forth in that article. It must however be 

 kept steadily in mind, that no complete 



Copyright, 1884, by Frank B. Webster and Eaton Cliff-. 



