18 
EIGHTH REPORT. 
ever, among those species in which the whole body of individuals swings 
northward and southward periodically and for long distances, at least 
20° to 25° of latitude or 1,200 to 1,500 miles. Among these are repre¬ 
sentatives of the most diverse orders and families with many peculiar 
and exceptional cases, yet much general agreement as to the main facts. 
Some go openly, in immense flocks, by day and in fair weather, as the 
swallows, sandpipers and crows; others, like the cuckoos, flycatchers 
and rails, are commonly believed to go singly and at night, and they 
drop aAvay so stealthily, even mysteriously, that this supposition seems 
justified. Many water-birds, geese, ducks and others, seem to wait for 
storms of wind or rain and to delight in making their long flights in or 
just before tempestuous weather. 
One of the older and seemingly well-grounded beliefs was that many 
of the smaller and presumably weaker migrants travelled entirely at 
night, partly to avoid the attacks of hawks and partly that they might 
rest and feed by day. The fact that multitudes of such birds do travel 
at night is undeniable, and perhaps the most marvelous demonstration 
of this is the discovery (first announced in October, 1880, by W. E. D. 
Scott) that this migration could be watched easily with a telescope 
trained on the face of the moon while within a few hours of the horizon. 
Yet the fact seems to have been very generally overlooked that night 
flying does not preclude day-flying, and that millions of small birds 
might pass over our heads at midday and in fair weather, and yet be 
just as invisible as at midnight, provided they flew at the heights 
claimed for the nocturnal migrants. Similarly, the fact that birds ap¬ 
pear by thousands about lighthouses and electric lights during cloudy 
and foggy nights carries not the slightest proof that the same species 
do not travel just as freely by day. As a matter, of fact we know that 
almost all the species killed at lighthouses do make long flights by day 
under favorable conditions, and an examination of all the accessible 
evidence leads me to assert that most birds do not fly at night to avoid 
enemies or escape observation, but merely to take advantage of favor¬ 
able conditions as yet but partially understood. Telescopic observa¬ 
tions at night have shown many small birds flying at heights 
of from one to three miles, and even at a height of a mile most of these 
same birds would be entirely invisible to the unaided eye in a clear sky 
at noon. Moreover, telescopic observations by day—the telescope 
trained on the sun—have shown in at least two cases birds flying at great 
heights, far above the reach of our unaided eyesight, and in one of 
these cases the birds were migrating southward in enormous numbers, 
the observer stating that “after watching for ten minutes there was 
no diminution.” This was at Shere, Guilford, England, at 3 p. m., on 
September 30, 1894.® 
From the above telescopic observation by daylight and from several 
similar ones at night the impression would be gained , that birds when 
migrating move at great heights, at least from one to three miles above 
the surface. One excellent authority, Mr. F. M. Chapman, speaking of 
results from his own telescopic observations, says: “We determined 
the greatest altitude at which birds migrate to be three miles 
many, however, fly at lower levels; indeed, it is not improbable that 
*R. A. Bray, Nature, Vol. 52, p. 415. 
