47 



lias just been said does not apply to Mr. Otto Widni arm's notes for 1885, 

 since, as in former years, he kept a full record of all the movements of 

 each species. 



In j)reparing this part of the report the chief endeavor has been to 

 trace the movements of the van of each srjecies, while the more im- 

 portant part, relating to the movements of the bulk, must be left un- 

 noticed. 



The departure of a bird from any point is necessarily followed by its 

 arrival at some other point ; so that when a departure is noted a cor- 

 responding arrival may be looked for. The record of a typical move- 

 ment of a species in its northern migration would contain : 1st, the 

 record of the earliest arrival ; 2d, the arrival of the bulk of the species 

 at a point somewhat farther south ; 3d, the departure of the bulk from 

 a point still farther south ; 4th, the departure of the last individual 

 from the southern limit occupied by the species on the same day. 



Such a contemporaneous record would prove that during the previous 

 night a general movement of the species had taken place. 



Were all the records as full as those of the first arrivals many such 

 typical movements undoubtedly would be found. This, however, would 

 be too much to expect. What we ought to find recorded is an arrival 

 of the bulk of a species for each corresponding departure, and when 

 the stations become sufficiently numerous, and the observers more 

 thoroughly trained, these important items will be forthcoming in many 

 if not in most cases. Then and not till then will something definite be 

 known concerning the distance actually traveled by birds during a 

 single night's migration. The computations based on first arrivals will 

 always be very uncertain, and if accurate information ever is obtained 

 it must come almost entirely from the movements of the bulk. * 



In the systematic portion of this report it has been found impracticable 

 to give in full all the notes contributed by the different observers, be- 



[* Again I am forced to differ with Professor Cooke. There is 110 evidence to show 

 that in any species of bird a sufficiently large proportion of the total number of individ- 

 uals comprising the migratory host move forward together afc one time to justify the 

 description of such a movement as that of " the bulk of the species. " On the con- 

 trary, migration consists of a series of successive movements or waves, each of which 

 brings a variable number of individuals to places a variable distance in advance of 

 the point or points from which they started. It was the recognition of these facts 

 that led me to omit reference to " bulk" movements in preparing the circular for 1885, 

 and to insert the following statement, of which Professor Cooke makes no mention: 



" The committee particularly desires exact records of every increase and decrease 

 in the numbers of a given species over a given area ; for it is only by the knowledge 

 of the daily fluctuations of the same species in the same place that the progress and 

 movements of a ' flight, ' or ' bird wave, ' can be traced. Such data can be contrib- 

 uted by experienced observers only, and in their procurement much time must be 

 spent in the field. During the progress of the migratory movement the observer 

 should go over the same ground day after day, and, if possible, both early in the 

 morning and late in the afternoon. He should visit woodlands, thickets of dense 

 undergrowth, and open fields; and, if possible, both swamp and upland should fall 

 under his daily scrutiny. "— C. H. M.] 



