g NORTH AMERICAN BIRDS. 



maritime portions of the United States, the European representatives of both 

 species being generally distributed throughout that continent. On the other 

 hand, the northwest-coast race of our Scops asio {S. kcnnicotti) seems to be 

 nearly identical witli the Japanese .S'. scniitorques (Schlegel), which is un- 

 doubtedly referrible to the same species. 



As regards their i)luinage, the Owls differ most remarkably from the 

 Hawks in the fact tliat the sexes are invariably colored alike, while from 

 the nest to perfect maturity there are no \\cll-marked progressive stages 

 distinguisliing the different ages of a species. Tlie nestling, or downy, 

 plumage, h(nvcver, of many species, has the intricate pencilling of the adult 

 dress rejilaced by a simple transverse barring updu tlie imperfect downy 

 co\ering. The downy young of Xi/dca scandiaca is plain sooty-lirown, and 

 that oi Strix Jlammca immaculate white. 



In many species tlie adult chess is characterized by a mottling of various 

 shades of grayish mi.xed witli ochraceous or fulvous, this ornamented by a 

 ^•ariabl(', often very intricate, pencilling of dusky, and more or less mixed 

 with wliite. As a consequence of the mixed or mottled character of the 

 markings, the plumage of the Owls is, as a rule, difficult to descriVje. 



In the variations of plumage, size, etc., w-ith differences of habitat, 

 there is a wide range, the usually recognized laws ^ applying to most of 

 those species which are generally distributed and resident where breeding. 

 Of the eight species common to the Palajarctic and Xearctic Realms, all but 

 one {Otus hmclnjotus) are modified so as to form representative geograpliieal 

 races on the two continents. In each of these cases the American bird is 

 much darker than the European, the brown areas and markings being not oidy 

 more extended, but deeper in tint. The dilference in this respect is so tan- 

 gible that an experienced ornithologist can instantly decide to which con- 

 tinent any specimen belongs. Of the two cosmopolitan species one, Otus 

 hrach/ohis, is identical throughout ; the other is modified into geographical 

 races in nearly every well-marked province of its habitat. Tims in the 

 Pakearctic Eealm it is typical Striv flammca ; in the Nearctic Eealm it is var. 

 jiratincola ; while Tropical America has at least three well-marked geo- 

 graphical races, the species being represented in Middle America by the var. 



piitiioly rpstricted to the western portion, or el.se are mueli more iilnindant there than in the 

 east. Tlie European genera Cinclu.i, Coccolhrauslcs, Nucifraga, and Cohimba have representa- 

 tives only in the western portion of North America. 



Instances of a similar relation between the plants of the Western Province of North America 

 anil those of Europe, and more striking likeness between the flora of the Eastern Region and 

 that of Eastern Asia, are beautifiilly explained in Professor Gray's interesting and instructive 

 pa|)er entitled "Sf(|uoia, and its History," an address delivered at the meeting of the American 

 Association for the Advancement of Science, at Dubuque, Iowa, August, 1S72. The poverty in the 

 species of tortoises, and richness in lizards, and the peculiarities of the ichthyological fauna, as well 

 as absence of fonnsof Western North America and Europe, coni|iared with Eastern North America 

 nud Eastern Asia, afford other examples of parallelism in other classes of the Animal Kingdom. 



' See Baird, Am. .Tourn. Arts and Sciences, Vol. XLI, .Ian. .and March, 1866 ; Allen, Bull. 

 Mus. Comp. Zool. Cambridge, Vol. II, No. 3 ; and Ridgway, Am. Joum. Arts and Sciences. 

 Vols, IV and V, Dec., ISTi', and Jan., 1S73. 



