38 ^24 



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 abun- 

 dantly 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 on 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 10 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 belaid not 

 in uninterrupted succession; but with that species at intervals of 

 indefinite duration during a lengthened period, foetation taking place 

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

 the young of each brood are widely different in appearance, accord- 

 ing 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, ne- 

 cessarily assist in 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 

 Prof. 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 



