206 
BULLETIN OF WISCONSIN NATURAL HISTORY SOCIETY. 
VOL. 2. NO. 4. 
made the voyage take the lead and retrace the path by which 
they came (49). The younger birds, born since the last journey, 
confine themselves to following their elders, and when, some 
months, later, it becomes time to return, they are able in their 
turn to follow in a reverse direction the journey previously made."' 
However, since migration is the result of dispersion, and dis- 
persion takes place very gradually, comparatively only a very 
short distance each year in the extension of a migratory route, the 
probabilities are that the features along this route are very fa- 
miliar to the older birds. With regard to those that were born 
since the last journey, there are again conditions that make a 
sixth sense entirely unnecessary. Brewster claims that young 
birds migrate by example, and his claims are upheld by the ma- 
jority of leading ornithologists (50). This being the case they can 
readily join the migrating stream overhead and without any great 
effort follow the general movement. When we consider that at 
Beloit from sixty to eighty birds crossed the field of vision in fif- 
teen minutes, showing that there is a regular stream of migrants 
along the highway, it leaves little room for doubting the ability of 
young birds to find their way without the aid of a sixth sense. 
CHAPTER IV. 
THE MANNER OF MIGRATION. 
The movements and habits of birds differ in different species, 
during the migratory season, with regard to one another and 
to their environment. These relations have been designated by 
the term Manner of Migration. 
The problems arising in this connection may be classified un- 
der three main heads : (i) with regard to their associations, which 
concerns itself with the questions of the numbers and species as- 
sociated during the migratory season, the relation of adults to 
young, and the relation of males to females ; (2) with regard to 
the environment, which concerns itself with the questions of 
special food habits, and meteorological influences; (1) with re- 
gard to the manner of progressing from place to place, which 
concerns itself with the time of migration — day or night, — the 
relative successive positions, the speed and altitude attained, and 
kindred phenomena exhibited during the time birds are in actual 
49. This he endeavors to show is accomplished by a sixth sense, a 
sense of orientation. 
50. Brewster. Mem. Nutt. Ornith. Club, No. 1, 1886, p. 12. 
