ALASKAN BIRD -LIFE 



General Characteristics 



The bird-population of Alaska is large, varied, and interesting, 

 despite the remote and northern situation of the country. This is^ 

 possible because it has a warm and moist summer, although a short 

 one, favoring the rapid and copious growth of vegetation, including 

 extensive forests; and because the adjoining seas abound in food 

 naturally attractive to many kinds of birds. 



Any map of Alaska showing average weather conditions makes 

 plain the fact that the lines (isotherms) which connect places in North 

 America having the same average summer warmth swing up in the 

 west far toward the north, proving — what is plain to all who live there 

 — that a climate as mild in midsummer as that of the Great Lakes 

 region prevails much farther toward the north on the Pacific than 

 on the Atlantic slope of the continent. 



The amount and character of the bird-population in any region 

 depend greatly on its having a climate favorable to birds at the season 

 when they are hatching and rearing their nestlings, not only because 

 most birds are creatures of mild rather than rough conditions, but 

 because a warm and moist climate furnishes far more food, both ani- 

 mal and vegetable, than does a cold or an arid one. The fact that 

 a temperate summer climate extends as far northwest as central Alaska 

 therefore allows the land-birds to spread their area of summer resi- 

 dence much farther in that direction than they are able to do on the 

 bleak northeastern side of the continent. For this reason Alaska has 

 many kinds of birds well known in the United States. 



Another reason why Alaska has a large bird-population is found 

 in the fact that the Pacific Coast and the long trough between the 

 Rocky Mountains and the Sierras .and northern coast ranges form 

 natural and unobstructed pathways for the migratory birds of the west 

 as they annually travel northward in spring and back again in autumn. 

 Another convenient and natural approach for migratory birds is from 

 western Canada down the upper Yukon Valley ; and probably most of 

 the small birds of the interior go and come by this river-valley 

 route. When to this mingled company is added the group of birds — 

 principally sea-fowl — that reside in the Territory all the year round 

 it is manifest that the bird-population of Alaska is not only extensive, 

 but is more representative of the whole of North America than that 

 of any other part of the continent. 



