OWLS. 323 



Most owls are arboreal in their habits, but with quite a fondness for rocks and 

 bushy cliffs, while very few are really terrestrial. In those which are most so, how- 

 ever, the claws are liable to be less curved. 



The food is quite variable, but owls destroy immense numbers of rats, mice, and 

 other ' vermin,' and are thus of incalculable service to man. Their habit (in common 

 with other Accipitres) of ejecting by the mouth the indigestible parts of their food, 

 renders the absolute determination of the character of their food comparatively easy. 

 This subject has been very thoroughly investigated of late years in Europe, and the 

 results show conclusively that while owls may occasionally do more or less damage in 

 the destruction of useful birds, this is more than compensated for by the wholesale 

 destruction of injurious rodents (especially Muridas and Arvicolidae) of which the 

 bulk of their food consists. 



Some forms feed largely on fish, which they catch for themselves, and it has been 

 frequently noticed that in such species the legs and feet are usually bare ; but, as Pro- 

 fessor Newton remarks, we must not be too hasty in drawing conclusions from these 

 facts, for the tarsi are also bare in some species which are not known to catch fish at 

 all, and, we may add, many species which sometimes fish for themselves have both 

 tarsus and toes well feathered. Indeed, the snowy-owl, with its feet so muffled in 

 feathers as even to hide the claws, was seen by Audubon catching fish very skilfully 

 from the * pot-holes,' at the falls of the Ohio at Louisville. 



Most owls follow the rule which obtains among other Accipitres as to relative size 

 of the sexes, the female being usually the larger, but there are some exceptions. The 

 sexes, however, are invariably alike in coloring, and the young do not seem to pass 

 through any well-marked ' stages ' of plumage after they once put off the down. 



Melanism and albinism are both rare in this family, but in a large number of species 

 belonging to several widely different genera, two phases of plumage occur indepen- 

 dently of age or sex ; one the ' gray ' plumage and the other the ' red,' the prevailing 

 color in the former being brownish gray, and in the latter rusty red. These phases 

 were for a long time a puzzle to naturalists, it being at first supposed that the two 

 colors marked different species ; later, that they indicated either different sexes or ages ; 

 while it is now pretty generally conceded that both colors may be found in young 

 from the same nest, offspring of the same parents, whether these be both red or both 

 gray, or one of each. Moreover, it would seem probable that either phase once 

 assumed is worn through life. Species in which both phases occur are often called 

 dimorphic or dichromatic. Further reference to this subject may be found in the 

 introduction to this volume (page 8). 



The nesting habits vary much, but the eggs are normally always white, either pure, 

 or yellow- or blue-tinted, and almost spherical. They are commonly more numerous 

 than in other Accipitres, being usually four to six ; but in several cases as many as 

 eight or ten are laid ; while in at least one species, and probably in more, the normal 

 number appears to be two. 



From the nocturnal preferences of most owls their habits are very slightly known, 

 and many interesting facts are doubtless to be discovered in this direction. More 

 often heard than seen, even their notes are only imperfectly known as yet, but are 

 ordinarily monotonous and mournful, occasionally pleasing and almost musical, while 

 the voices of some species appear never to have been heard. As to the manner of 

 flight and method of hunting in nocturnal forms we know very little, and our infer- 

 ences from structure must be of the most general kind. 



