40 
or injury. In the spring the order is altered, the adult maleg 
leading, the females following, then the young birds, and lastly the 
injured or weakly ones. The time of day of migratory flight 
varies a good deal. Some birds migrate by day, but the great. 
majority do so at night or above the range of human vision. The 
punctuality of the arrival of birds is very remarkable. Some may 
be looked for almost to the day after a flight of some thousands 
of miles. Thearrival of some sea birds at their breeding places is: 
so regular that it forms a date in the calendar of men most con- 
cerned in the event. The date varies much with different species, 
some arriving earlier, some later, but as a rule the first to arrive 
«are the last to depart, and the last to arrive stay the shortest time, 
and are the first to leave. 
During the height of migration, unfavourable weather will 
sometimes delay a considerable number of migrants, and then a 
favourable change will cause an immense rush of innumerable. 
birds, these rushes being more frequent in autumn than spring. 
Perhaps on no point of migration is there greater difference of 
opinion than on the question of speed. Whilst some observers 
consider 2,000 or 8,000 miles in one night is nothing unusual, 
others consider about 800 miles in 24 hours to be a good average. 
Some observers think that birds travel by stages, staying here and 
there on the way to rest; others that they usually perform the 
greater part of the flight of 2,000 miles or more in one or two 
stages. The dotterel breeds on the tundras of Arctic Europe and 
Asia, and winters in Africa, north of the equator. Its spring 
migration is late and rapid, and as the bird is scarcely ever seen in 
intermediate localities during this season (Heligoland records but. 
few in May), we are forced to the conclusion that this enormous 
flight of quite 2,000 miles is performed without a rest, and between 
sunset and sunrise. Ifthe dotterel were to start in the evening 
gloom from its African haunts, say at 7 p.m., it would reach the 
moors of the Arctic regions, by flying 200 miles per hour, about. 
five the following morning—a record of speed that makes the 
highest pace of our ‘* Fying Scotchman,” ‘‘ Wild Irishman,” or 
“‘ Dutchman,” appear but the creep of a snail by comparison, and 
of astounding endurance, which may well fill us with genuine 
admiration and wonder. This account is given by Mr. Charles 
Dixon in his book, ‘‘ The Migration of Birds,’ from which I have 
derived much of what I am narrating to-night. But, on the 
opposite page, he has already written that probably migratory 
birds do not average more than 800 miles per day. I shall refer 
later on to this question of speed and other disputed points when 
I tell you of Herr Giatke’s work in Heligoland. Let us now 
consider the height at which birds fly during migration. This is 
