A Quantitative Study of the Nocturnal Migration of Birds
BY
GEORGE H. LOWERY, JR.
University of Kansas Publications Museum of Natural History
Volume 3, No. 2, pp. 361-472, 47 figures in text June 29, 1951
University of Kansas LAWRENCE 1951
UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY
Editors: E. Raymond Hall, Chairman; A. Byron Leonard, Edward H. Taylor, Robert W. Wilson
UNIVERSITY OF KANSAS Lawrence, Kansas
PRINTED BY FERD VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1951
[Union Label]
23-1020
A Quantitative Study of the Nocturnal Migration of Birds
By
GEORGE H. LOWERY, JR.
CONTENTS
Page
INTRODUCTION 365
ACKNOWLEDGMENTS 367
PART I. FLIGHT DENSITIES AND THEIR DETERMINATION 370
Lunar Observations of Birds and the Flight Density Concept 370
Observational Procedure and the Processing of Data 390
PART II. THE NATURE OF NOCTURNAL MIGRATION 408
Horizontal Distribution of Birds on Narrow Fronts 409
Density as a Function of the Hour of the Night 413
Migration in Relation to Topography 424
Geographical Factors and the Continental Density Pattern 432
Migration and Meteorological Conditions 453
CONCLUSIONS 469
LITERATURE CITED 470
LIST OF FIGURES
Figure Page
1. The field of observation as it appears to the observer 374
Table of contents (by pages)
- 1: A Quantitative Study of the Nocturnal Migration of
- 2: Iowa 377 5
- 3: Hourly station density curve at Progreso
- 4: Since that time the volume of field data
- 5: Lowell Wood for their assistance
- 6: Many of these persons stayed at the telescope
- 7: Chief of the Climatological and Hydrologic Services
- 8: Small as these silhouettes are
- 9: 2 their altitude above the earth
- 10: Expressed in radians see Figure 2
- 11: Based on observations at Ottumwa
- 12: The ellipse becomes greatly elongated
- 13: The sampling effect of a square
- 14: Is the angle of the true cooerdinate
- 15: In fields of observation of different sizes
- 16: And using vector analysis to obtain a vector resultant
- 17: Altitude as a Factor in Flight Density A flight density
- 18: If it were applied to present altitudinal data
- 19: Yucatan OBSERVERS Harold Harry
- 20: The identification of cooerdinates
- 21: Continuation of Data in Figure 12
- 22: With the aid of a reverse equation
- 23: Standard sectors for designating flight trends
- 24: When the GHA is less than the local longitude
- 25: Representing the sector density
- 26: The evolutionary origin of migration
- 27: And a large segment of the migratory movement can be studied
- 28: In sixty percent of these instances
- 29: Stebbins saw seventeen and Carpenter
- 30: Have imposed their own characteristics on the final graph
- 31: Various types of density time curves
- 32: Six dissimilar types are shown
- 33: They begin to exhibit migratory restlessness
- 34: A somewhat more normal density pattern is manifested
- 35: If the flight is concentrated along a river
- 36: Especially convincing to him were results obtained at Beloit
- 37: Thus the prevailing direction of flight
- 38: Where the vector resultants were 21 deg
- 39: The general results are summarized in Tables 2 5
- 40: Progreso 11
- 41: I know that migrants reach Texas from the first source
- 42: Computed Hourly Densities at Tampico
- 43: Forty five hours of observation at Tampico
- 44: I returned in 1948 by freighter to Progreso
- 45: Computed Hourly Densities at Progreso
- 46: In view of the volume of migration departing from Progreso
- 47: The corresponding ground density of 2
- 48: Where densities decline abruptly well before midnight
- 49: We have the results from Rosedale
- 50: A surprisingly low flight density
- 51: The location of high and low pressure areas
- 52: The direction of the net trend at Progreso
- 53: As shown by the vector resultant
- 54: Pensacola migration negligible 20
- 55: Migration at Ottumwa was comparatively low 6
- 56: Followed by a pronounced decline
- 57: Meteorological and climatological data for April 1948
- 58: Evidence of trans Gulf migration
- 59: Lowery on trans Gulf migration