All major kills occurred on cloudy and foggy nights associated with frontal weather. Throughout the period a few birds struck the tower even on fairly clear nights, and minor but appreciable "falls" occurred on the nights of October 4-5, 7-8, and 22-23. A few birds killed probably were overlooked for a time and found their way into later samples. This is especially probable in the case of some birds entered under date of October 23, as many of these were somewhat desiccated. Weights clearly altered by desiccation or mutilation were not recorded. Reports of these accidents have been published by Carson (1954 a, b, and c).
According to Carson (1954c:27), the majority of birds killed on nights of heavy flight fell "between three and four o'clock in the morning when skies were overcast and a cool front moved in from the north. Due to the cooperation of the watchmen it is thought that most of the birds that were killed were recovered. Of course some injured birds in hiding were not found and some were lost to predators."
Description of WIBW-TV TOWER.—The tower is 950 feet tall and stands on a hill approximately 1000 feet above sea level. The fact that the tower is on a hill places the top of the tower at 1010 feet above the elevation of the average local terrain. The tower is triangular in cross-section, each face seven feet wide, and is constructed of six-inch steel L-beams with three-inch cross-members every seven feet and smaller diagonal cross-members. It has no taper and bears a transmitting antenna on the top. The tower is supported by 12 guy wires, 3 wires attaching at each of 4 levels. The cables extend south, WNW, and NNE from the tower and are 1-1/2 inches in diameter. The tower is lighted by a series of red lights, some flashing and others steady. The transmitter was not in operation when the accidents took place.
Weather conditions.—All major kills at Topeka occurred when migrating birds encountered either a cold front or a stationary front lying over eastern Kansas. Typically, this frontal weather included rain, fog, and cloud ceilings down to as low as 800 to 1000 feet. Weather of this type presumably forces the migrating birds to fly below the cloud ceiling and thus brings them within the altitudinal range of the television towers.
Acknowledgments
We gratefully acknowledge our debt to the Topeka Audubon Society for making this study possible by carefully collecting birds killed at the television tower. L. B. Carson deserves special mention for his general supervision of the bird collecting by the members of the Topeka Audubon Society. Members of the Society and others who picked up birds under the television tower were: Mrs. Lloyd Biggs, Elaine Carson, L. B. Carson, Jesse A. Eddy, Elizabeth Fisher, Mrs. Walter Huxman, Florence McKinney, Mrs. Charles Martin, Mrs. Fred P. Martin, T. W. Nelson, Fred Prebble, Grace Prebble, Orville Rice, Mrs. G. Warren Scholl, E. W. Senne, and Beatrice Swenson.
We received equally important assistance from students and staff of the University of Kansas in recording of data and preparation of specimens. The following helped in these ways: Rollin H. Baker, R. W. Dickerman, David L. Hardy, J. W. Hardy, Jane S. Mengel, Larry D. Mosby, Richard Van Gelder, South G. Van Hoose, and Glen E. Woolfenden. We are indebted to the Interlibrary Loan Service of the University of Kansas Library for help in securing certain reference works. Robert Sokal of the University of Kansas gave helpful advice concerning statistical procedures.