Animal
The nocturnal migration of birds is a phenomenon that long has intrigued zoologists the world over. Yet, despite this universal interest, most of the fundamental aspects of the problem remain shrouded in uncertainty and conjecture.
Present day concepts of the whole broad problem of bird migration are made up of a few facts and many guesses. The evolutionary origin of migration, the modern necessities that...
5. PART I. FLIGHT DENSITIES AND THEIR DETERMINATIONThe subject matter of this paper is wholly ornithological. It is written for the zoologist interested in the activities of birds. But its bases, the principles that make it poss...
6. Part II of this paper is speculative in intent, and most of theconclusions suggested are of a provisional nature. Yet, compared with similar procedures in its field, flight density study is a highly objective method, and a relatively reliab...
3. PART II. THE NATURE OF NOCTURNAL MIGRATION 408The nocturnal migration of birds is a phenomenon that long has intrigued zoologists the world over. Yet, despite this universal interest, most of the fundamental aspects of the...
4. Part I of the present paper, dealing with the means by which the datawere obtained and processed, will explore the general nature of the problem and show by specific example how a set of observations is prepared for analysis. Part II will deal wi...
1. Volume 3, No. 2, pp. 361-472, 47 figures in text2. PART I. FLIGHT DENSITIES AND THEIR DETERMINATION 370