12 MEMOIRS OF THE NUTTALL ORNITHOLOGICAL CLUB. 



As is well known there are certain definite routes or paths of migration 

 along which birds pass in especially great numbers. These are usually 

 coast lines, river valleys, or continuous mountain ranges. Towards them 

 converge innumerable less frequented paths, each of which in turn has still 

 smaller tributaries of its own. Thus bird streams, like brooks, flow into 

 common channels, and each particular region may be said to have its bird, as 

 well as water, shed. An important consideration is that the tributary bird 

 streams follow courses in no wise strictl_y dependent on points of compass. 



Bearing these facts in mind, the manner in which birds find their way 

 seems very simple. From the height at which they fly the country presents 

 the appearance of a map on which, in the light of the moon or stars, the 

 mountain ranges, plains, lakes, rivers, and sea coasts are more or less dis- 

 tinctly outlined for a hundred miles or more in every direction.* Guided by 

 such landmarks the older birds can have no difficulty in following paths 

 which they have repeatedly traversed before, and they unquestionably 

 direct and perhaps lead all the larger flights, although it is by no means 

 certain or even likely that they do this in a systematic manner, or that their 

 leadership is distinctly recognized or realized by the younger birds who 

 accompany or follow them. On the contrary the latter are probably directed, 

 as well as perhaps urged onward, simply by the contagion of general ex- 

 ample and a desire to keep within sight or hearing of their companions ; 

 both strong influences with birds, especially very young ones which have 

 only lately passed from a state of complete dependence and are still not 

 wholly independent. That a very few experienced old birds could thus 

 direct and guide the movements of thousands of inexperienced young is 

 to my mind obvious, but the point perhaps calls for further discussion and 

 explanation. 



There are various instances on record of migratory birds, such as Geese 

 and Ducks, which, in confinement, have shown unmistakably, at the proper 

 season, an absorbing desire to set out on their accustomed travels. That 

 such an impulse is very general, and in most cases probably irresistible, 

 with old birds, is certain. It is not, however, equall}' clear that it is inborn, 

 at least with all birds. I grant that it may be so with many and probably 

 is so with some. But example is a strong influence with all creatures of 

 limited reasoning powers, and it seems to me sufficient to explain the 

 migratory movements of most small birds. The young, at first led about by 

 their parents, soon join other broods, and very quickly large flocks are 

 formed. In these flocks there are always a few old birds which, when the 

 proper time came, would set the example by mounting into the air and 



♦Anyone who has spent a clear night on the summit of a mountain will not question this 

 statement. 



