Birds observed in Kamchatka. 
275 
to that of the environment generally. The phenomena are 
not, in fact, the product of a single influencing factor, but 
of a combination of, probably highly complicated, influences, 
and the working of any particular one of which can only be 
positively identified when it acts with a force which greatly 
exceeds that of all, or of the majority, of the remainder. 
We have much evidence that dryness or moisture, absence 
of sunshine, and dull skies, together with purely local con¬ 
ditions, each have their influence on animal coloration, no 
less than direct differences in degrees of heat and cold, so 
that I would not like to refuse to climatic influences their 
due in the guidance of the evolution of the peculiar Kam¬ 
chatkan birds until all other explanations have been found 
wanting. 
The peculiar Kamchatkan birds are— Urogallus parvirostris 
kamtschaticus, Astur candidissimus, Haliaetus hypoleucus } 
Dryobates purus, D. immaculatus , Picoides albidior , 
Pica camtschatica, Nucifraga kamchatkensis , Parus kamts- 
chatkensis, and Sitta albifrons. 
Unfortunately we know very little about these peculiar 
species. Of several of them even Dr. Stejneger had seen 
no specimen. It is significant that one of those with which 
we are most acquainted, viz. the Magpie, is not only charac¬ 
terized by its whiteness, but is the largest form of Magpie 
known to Dr. Stejneger (being larger even than the Central 
Asiatic Pica leuconotos Brehm), so that, apart from its 
coloration, its size reminds us of the representative northern 
forms of some of our own common birds, such as the Redpolls, 
Bullfinches, Wheatears, and Lapland Buntings, and seems 
certainly indicative of severity of climate. One feature 
seems to be common to all : they are birds in which 
there is no conspicuous seasonal change of colour, so that 
the plumage suitable for the colder seasons of the year must 
be worn throughout the summer, or not at all. 
Lastly, these ten birds are nearly all sylvan forms, and 
may be included among the more sedentary species resident 
in Kamchatka throughout the year and unlikely to face the 
passage of the surrounding oceans, it may be, then, that 
