Life History of the Cactus Wren. Part I: Winter and Pre-Nesting Behavior

Abstract

This life history study of the Cactus Wren (Campylorhynchus brunneicapillus) began as an endeavor to determine the actual behavior of a small population of wrens in the vicinity of our home near Rillito Creek, at the northeast edge of Tucson, Arizona. A few supplementary observations were to be made in other places for the purpose of checking our local findings, but travel restrictions of World War II interfered somewhat. After the war, however, permission was obtained from the United States Forest Service to work on the Santa Rita Experimental Range, 30 miles south of Tucson. This made possible the study of population problems in a larger area. In addition to the field work, all the important published references in the ornithological literature were examined to obtain the views and data of other workers on this species. Our field notes, based entirely on observations of living birds, cover a period of about twenty years. No specimens were collected; we tried to disturb the birds as little as possible. Progress was slow at first because of the difficulty of working with a species in which the sexes are identical in appearance. Later, from 1939 to 1949, when color banding of adults and nestlings was consistently practiced, information of more reliability was obtained. Since the investigation was conducted entirely in our spare time, on mornings, evenings, and week-ends, there were many delaying interruptions and digressions. There are as a consequence many incomplete records. Nevertheless, we feel we have gathered enough data to reveal a fairly clear picture of the behavior patterns of the Cactus Wren. It should be emphasized that our local population, living in a suburban environment and constantly harassed and disturbed by human activities, may not have been truly representative. Life in more open, natural, desert surroundings may be somewhat different. In some respects it is perhaps harder; predators are more numerous, and food supply may fluctuate to a greater extent than in the vicinity of human establishments. In the main essentials, however, we found that the pattern of activity was the same on the desert range as that in our back lot. To Walter P. Taylor should go the credit for suggesting this fascinating problem. We wish to express our thanks to W. H. Behle, Herbert Friedmann, L. M. Huey, Seth Low, M. M. Nice, and A. L. Rand for aid in searching out bibliographic references, distribution records, and nesting areas; to Alden H. Miller and Frank A. Pitelka for advice on preparation of manuscript; to J. T. Marshall, Jr., and A. R. Phillips for nesting data; to J. J. Thornber, L. Benson, and C. T. Mason, Jr., of the University of Arizona Department of Botany for many courtesies in identifying plant specimens; and to J. E. MacDonald of the Institute of Atmospheric Physics at the University of Arizona for help in securing climatological reports. We are deeply grateful to Raymond Price, who, as director of the Southwestern Forest and Range Experiment Station in 1953, granted us permission to work on the Santa Rita Experimental Range; we are also indebted to H. G. Reynolds and S. C. Martin, who extended this courtesy in succeeding years and made accessible to us their valuable data on the range.