VIII 
indeed met with a far greater success than any of his predecessors 
is of course above all due to the faet that postal facilities are 
greater and education more universal now than they were even 50 
years ago, but we must also admit that he was happy in his way 
of starting the work. As he writes himself of his experiments it was 
not the fixing of an aluminium ring to the foot of a bird which was 
the new idea, but that a great number of birds were being ringed 
in this way, and that every single bird had a special number on 
its ring allowing exact identification by a catalogue which was being 
kept simultaneously, and finally that the ringing was mentioned in 
the newspapers, and in scientific periodicals abroad. A more extended 
experiment was made in 1899 when rings were fixed on 165 
starlings. Though this experiment proved a failure Mortensen un- 
dauntedly persevered, assisted by a number of mostly young and 
interested helpers, indefatigably ringing year by year, and at the 
same time extending the work to include a series of different 
birds, such as teal, pintail, guils, stork, heron, birds-of-prey, etc. 
In 1912 he had succeeded in ringing 3540 birds in all, and at 
his death the number had inereased to about 6000, the rather 
considerable expense of this work being covered by grants from 
the Carlsbergfond. It is not astonishing that information has been 
obtained only about a fraction of this great number of birds; in 
1912 Mortensen himself only calculated to have heard about 6% 
or, the great number of starlings not being counted, about 14%. 
Of certain species such as teal, 1 ) pintail, 2 ) stork, 3 ) gulis, 4 and heron 5 ) 
he nevertheless succeeded in collecting sufficient data to illustrate 
their migration. An especially interesting result has been obtained 
in the case of the stork which we have been able to follow during 
its autumn passage down through Prussia and Hungary across 
Asia Minor and Syria to Tanganyika and the Transwaal. 
Mortensen s accounts of the ringed birds are, like everything 
that he has written, given with the utmost exaetness. The what 
may seem to outsiders too great emphasis on points of minor im- 
9 Teal (Anas crecca L.) in winter. Vid. Medd. naturh. Foren., LX, 1909. 
-) Mærkede Spidsænder. Dansk ornith. Foren. Tidsskr., VIII, 1913 — 14. 
s ) Mærkede Storke. Ibid., XIV, 1919—20. 
4 ) Mærkede Maager. Ibid., XVI, 1922. (Edited by his wife). 
5 ) Mærkede Hejrer. Ibid., XVI, 1922. (Collected and edited by S. M. Saxtorph). 
