Vou. II, Pr. IT] LOOMIS—A REVIEW OF THE TUBINARES 31 
where food is wanting and birds absent, and we know that 
there are prevailing ocean and air currents. It is in these cur- 
rents, I believe, that we shall find the chief physical phenomena 
guiding birds in their return-migration to islands remote from 
continental areas, on the ocean prevailing water and air con- 
ditions supplementing landmarks. It is a significant fact that 
the southern limit of the Black-footed Albatross’s range coin- 
cides well with the northern limits of the northeast trade- 
winds.* 
In accordance with the facts set forth above, it is asserted 
that the example? of the adults would suffice to teach the way 
to a young Black-vented Shearwater, or Black-footed Alba- 
tross, imbued with a desire for travel and keenly alive to 
physical phenomena; migration being the result of individual 
experience, at most only the tendency to migration being inher- 
ited. 
Habit 
After the way had been learned by the bird-of-the-year and 
a probable innate desire for travel had developed into migra- 
tion, the habit of migration would be formed and become sec- 
ond nature in each bird, holding it true to time and place. 
The force of habit is thus succinctly stated by Dr. C. Lloyd 
Morgan: “In its early days the developing animal is reading 
the paragraph of life. Every sentence mastered is built into 
the tissue of experience, and leaves its impress on the plastic, 
yet retentive brain. By dint of repetition, the results of acqui- 
sition become more and more firmly ingrained. Habits are 
generated; and habit becomes second nature. The organism 
which to begin with was a creature of congenital impulse and 
reaction becomes more and more a creature of acquired habits. 
It is a new being, but one with needs not less imperious than 
those with which it was congenitally endowed.’ 
1See part VI, also Barrett-Hamilton, Ibis, 1903, p. 320, and Salvin, Voy. Chall., 
Zool., v. 2, pt. 8, p. 147. 
Furthermore, winds prevailing for the time being may afford a means of guidance 
to low-flying migrants journeying across narrow seas; cf. Clarke, Studies in Bird 
Migration, v. 1, pp. 172, 173, 176-178, v. 2, pp. 12, 28, 29. 
2In some instances, at least, direct leadership seems to be exercised. In a former 
paper (Proc. Calif. Acad. Sci., 2d ser., v. 5, p. 198) I cited an instance where a 
Sooty Shearwater apparently ordered a flank movement in a whole column of Sooty 
Shearwaters. ‘The intelligence of migrants, I believe, is generally much underrated; 
in supplemental movements, at least, there appears to be an appreciation of the necessity 
for migration. 
3 Nature, 1898, v. 57, p. 329. 
