31 
they were round as a ball, provided with a roof, and loosely 
composed of fine grass bents, but without feathers or hair.* 
The Siberian Willow-Wren with us, generaliy inhabits 
ground which is especially favourable for the development of 
the summer plague of Finmarken—the mosquitoes. From these 
they procure their food, and several times while the author 
has stood still to discover the secrets of the habits of this char- 
acteristic species by watching, it has through the mosquitoes 
been rendered almost an impossibility. 
In the birch woods of M we meet, however, not only with 
species of purely arctic origin. Several genuine birds of passage, 
belonging to the common European fauna, also have here their 
furthest boundary towards the north, and the well-known notes 
of the Garden Warbler and the Blackcap (Sylvia hortensis and S. 
atvicapilla), the Redstart (Auticilla phenicurus), the two Fly- 
catchers (Muscicapa atricapilla and M. grisola), the Tree Pipit 
(Anthus trivialts), the Song Thrush (Turdus musicus), the Hedge 
Sparrow (Accentoy modulavis), and several others, meet us fre- 
quently. They are the same forms here as in the south; the 
song, however, is not quite the same; it has a somewhat muffled 
sound, and even a few of the strains are partly different and 
unknown. And this allows of an easy explanation. Up here, 
where the areas are so large and the total number of spots habit- 
able by these species few and far between, individuals frequently 
have no opportunity of hearing another of his own kind; each 
male sings only for his own mate, and competition can never arise, 
since it but seldom hears one of the same species as itself. Each 
one evolves his song independently of any influence from others, 
and they thus, therefore, acquire their individual impress. 
Of other acquaintances from the lowlands, which meet us in 
the Finmarken valley bottoms, we may mention the House 
Martin (Chelidon urbica). In these desolate regions, this bird also 
knows how to adapt itself to its surroundings. As in Finmarken 
they only rarely find nesting-places on the few and low houses, 
they therefore breed in colonies, several hundred pairs together, on 
* One of these broods is to be seen exhibited at our Zoological Museum (in 
Christiania), all the young ones sitting by the side of each other on a branch, the 
only young of that species that are as yet known to be exhibited. 
