to get such information and a new method may have to be devised. 
Another aspect of the research will be to test the hypothesis that the 
Alaska summer gives the birds a major advantage by permitting a 
shorter nesting period. This can be done by making comparisons of . 
growth rates of the same species nesting at’ high and low altitudes, and 
of the mortality during this period of their lives. 
Studies like these must be regarded as fundamental biology. But 
even though concrete results cannot be foreseen at present, scientific 
history should make us cautious in predicting that practical applications 
will not eventually be forthcoming. Until they are, however, we must 
just regard our research as a quest for understanding of a major bio- 
logical problem. Certainly it is a fascinating one and a mystery that 
has intrigued men throughout the ages. I suggest that the phenomenon 
of bird migration be born in mind by readers during air travel when 
visual contact with the ground is obstructed by darkness or by clouds. 
It is at such times that the accurate navigation of these “citizens of the 
sky” most strongly arouses. our intellectual curiosity, admiration 
and respect. 
Bibliography 
Frisch, Karl von, Bees, their vision, chemical senses, and lan- 
guage. Cornell University Press, 1950. A short, readable book de- 
scribing the surprisingly complex behavior of honeybees, especially 
their use of the sun and the polarization of the light from the sky ina 
sort of celestial navigation. 
Gordon, D. A., Sensitivity of the homing pigeon to the magnetic 
field of the earth. ’ Science 108: 710-7 ii. 1948. A technical report of 
negative results in an effort to repeat one of the key experiments upon ~ 
which was based Yeagley’s theory of bird navigation. 
Griffin, D. R., The sensory basis of bird na navigation. Quarterly 
Review of Biology 19: 215-31, 1944. A review of the many diverse scien- 
tific papers on experiments with homing and migration. 
Griffin, D. R., and R. J: Hock, Airplane observations of homing 
birds. Ecology 30: 176- 198, .1949. Detailed r report on experiments in 
which gannets were carried inland, released in unfamiliar territory and 
followed from a light airplane during the first few hours of their 
homing flights. 
Griffin; D. R., The Navigation of Birds. Scientific American - 
179:18-25, December, 1948. A semi-popular account of various ex- 
periments that have revealed something about the ability of birds 
to navigate. 
Henshaw, H. W., Migration of the Pacific golden plover to and 
from the Hawaiian Islands. The Auk, 27:245-262, 1910. An ornitho- 
logist’s account of the evidence he could obtain over 40 years ago con- 
cerning the over-water flights of this spectacular migrant. 
Lowery, G. H., A quantitative study of the nocturnal migration of 
birds. In preparation by the University of Kansas Museum of Natural 
4H19.= 
