VII 
Of the different vertebrates the birds were decidedly his favour- 
ites, and even during a very early period of his life, while private 
tutor at Bregningegaard, he founded a collection of birds’ skins 
which he prepared himself. He got such an insight into this matter 
that he was able to publish later on a useful little guidebook. 1 ) 
After his appointment to Viborg he met with two prominent ornith- 
ologists, Mr. A. Hagerup, architect, and Dr. P. W. Heiberg, 
head physician of the diocese, a circumstance which no doubt 
greatly contributed to reviving and strengthening his ornitholog- 
ical interest. Through these two scientists with whom he was in- 
timately connected he further became acquainted with a whole 
group of other ornithologists, as f. inst. Dr. O. Helms, chief surgeon. 
With the greatest interest he kept in contact all his life with phen- 
omena within the Danish ornithological worid, being one of the 
little number of ornithologists who founded Dansk ornithologisk 
Forening, October 15th 1906. 
His special studies were particularly directed towards the bio- 
logical side of ornithology which it was his object to clarify in 
every detail. He spent much time in thorough observations which 
were conscientiously noted down. His special favourite among the 
birds was the starling, the life and doings of which were excel¬ 
lently described by him in a booklet, published in 1905. 2 ) He was 
also intensely interested in securing definite facts concerning the 
migration of this bird, an interest which led him to attempt ring- 
ing. Unfortunately it turned out later on that for different reasons 
the starling was not a very good choice for these experiments. 
Of ringing, its history, technique, and the results attained so 
far, he himself in 1912 gave a detailed account 3 ) to which we 
here refer. It appears from this account that the idea of fixing to 
a bird’s foot a ring carrying an inscription was not new at all, 
inasmuch as the first experiments may be traced as far back as 
to 1806, and, further, that they had sporadically been made in the 
19th century, without however leading to any special results. That 
Mortensen ventured upon a resumption of these experiments, and 
9 Anvisning til at udstoppe og opbevare Fugleskind. Viborg, 1889. 
2 ) Stæren, Myreløven og andre Skitser fra Dyrelivet. Kbhvn. 1905. 
8 ) Fra Fuglemærkningsstationen i Viborg. Dansk ornith. Foren. Tidsskr., 
VI, 1911 — 12. 
i 
