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yet been satisfactorily investigated. No doubt its presence is partly owing to a temporary 

 migration to spots wbere its favourite food is suddenly produced in such abundance. Later in 

 the season the number of individuals is doubled, which, indeed, is not surprising, as procreation 

 in a species as a rule increases simultaneously with the supply of food. 



" Now it is a well-known fact that many birds breed more abundantly when food is plentiful 

 than under ordinary circumstances. This, for instance, has been shown to be the case with 

 several species of the owls that prey principally on small rodents, which in certain years are 

 exceptionally numerous; but whether such increase in the procreative powers is owing to the 

 abundant supply of food, or is to be traced rather to the cause (whatever it be) which renders 

 the small rodents in that very year so much more prolific than common, is still an open question. 

 Neither in Valders nor on the Hallingdal fells was there a migration of lemmings that year ; but 

 there, too, the Snowy Owl appeared in large numbers. 



" Meanwhile it is a fact that the Snowy Owl does not always lay so many as ten eggs at a 

 time : it did so, however, last year in many cases ; and the various circumstances attending the 

 phenomena are not without interest. 



" As with all birds of prey, the eggs would appear to be laid not in uninterrupted succession, 

 but with that species at intervals of indefinite duration, during a lengthened period, fructuation 

 taking place previous to the laying of each egg. A natural consequence is, that the young of 

 each brood are widely different in appearance, according to the stage of growth which each has 

 attained. Thus the first of the brood will be almost fledged before the last has broken the 

 shell. And, again, the nestlings, thickly clad with down, necessarily assist in the process of 

 incubation ; the old birds have enough to do to provide for the young already hatched, several 

 of which, being more than half-grown, require a good deal of food. 



" A nest, located in a hollow on the bare ground, was found by Professor Friis, July 6th, 

 1872, on the fells in Ringebo, Gudbrandsdalen. The brood were in four stages of growth. 

 Four (of the size of a Hazel-hen) were half-grown, the wings being partially developed ; two were 

 considerably smaller; and the remaining three were nestlings just hatched; finally, under the 

 young there was an egg in an advanced stage of incubation. There was evidently an interval of 

 several days between these stages. On the following day a pair of Snowy Owls were observed 

 in copuld", and hence eggs were still being deposited in their nest. The male belonging to the 

 first nest was shot, and proved to be a very old bird, perfectly white, with the exception of a 

 few darkish spots on the tips of the wings. 



"Many of the nests were found that year on the fells in Gudbrandsdalen; and throughout 

 the summer the 'Kvitorn' (lit. White Eagle) was seen in almost every spot. On the shore these 

 birds were seen for hours perching on the telegraph-poles, and were hardly to be driven off with 

 stones. 



" In Valders and Hallingdal no less than twenty-nine eggs, taken from nests near Nystuen, 

 on the Fillefjeld, were collected by one collector, Mr. Lysne ; but as these were not left in the 

 nest, the observations could not, as with those made by Professor Friis, be repeated. Here, too, 

 the eggs were laid at irregular intervals the whole summer through ; eggs in an advanced stage 

 of incubation were found on the 1st June (probably their usual breeding- time), and fresh eggs 

 on the 17th June, and even the 19th July. 



