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Impact of Red Fox Predation on the Sex Ratio of Prairie Mallards


A study of this scope would be impossible without the generous assistance of numerous individuals, to whom we are most grateful.

Several U.S. Fish and Wildlife Service (USFWS) personnel provided information pertaining to mallard population dynamics. D. R. Anderson contributed data on survival and hunting recovery rates of birds banded in North Dakota and nearby areas, C. F. Kimball supplied information on the rate of retrieval of hunter-shot mallards, C. J. Henny and K. P. Burnham provided preliminary results of a study of band reporting rates, and R. S. Pospahala furnished mallard population estimates for our reference area.

The determination of red fox predation rates on mallards required rather precise information on several aspects of fox biology and population dynamics. Pertinent data of this nature were provided by several individuals. G. L. Rohde furnished results on the disposition of adult mallards taken by red foxes. Rohde and G. L. Storm provided data on the number of dens used by foxes to rear their litters. S. H. Allen, R. V. Hanson, and W. K. Pfeifer supplied fox population indices.

Some of the spring sex ratio counts used in this report were collected by M. C. Hammond, and were organized and cross-referenced by R. H. Town and L. C. Hagen. L. M. Kirsch provided mallard sex ratio data gathered near Woodworth, North Dakota.

Several individuals contributed substantially to the tedious task of excavating fox dens and retrieving waterfowl remains. Much of the field work was a cooperative venture with the North Dakota Game and Fish Department. We are especially grateful to that agency for the assistance of S. H. Allen, D. T. Allen, W. H. Howell, and E. K. Fritzell. Others who worked on that study and were supported by the Northern Prairie Wildlife Research Center are R. T. Eberhardt, J. F. Wolf and G. L. Rohde. In addition, numerous personnel of the North Dakota Game and Fish Department and the USFWS provided waterfowl remains from fox dens they encountered during their field activities.

Writing the historical aspect of this study was greatly facilitated by the North Dakota Game and Fish Department. In particular, W. Boldt granted the use of M. Johnson's records of interviews with North Dakota "old-timers," and C. R. Grondahl supplied Figs. 10 and 11. We also appreciate the discussion with W. K. Pfeifer, USFWS, concerning the history of canids in North Dakota.

The field work involved in the study and much of the analysis was performed while H. K. Nelson was Director of the Northern Prairie Wildlife Research Center. Most of the writing was carried out while W. R. Goforth was Director. We appreciate the support and encouragement offered by both of them and by H. F. Percival, USFWS-- Washington.

Our report benefited greatly from critical readings by several reviewers. While grateful for their criticisms and suggestions, we retain responsibility for remaining errors, misinterpretation, and errant speculation. D. R. Anderson, K. P. Burnham, E. K. Fritzell, K. F. Higgins, L. M. Kirsch, H. W. Miller, H. K. Nelson, E. M. Preston, R. I. Smith, and G. R. Storm read all or portions of a previous draft and offered comments. We are particularly indebted to F. C. Bellrose and A. Dzubin, whose earlier work with waterfowl sex ratios laid the foundation for our own, for generously taking the time to perform a careful review of the report, and to T. S. Baskett for a thorough final review.

We also appreciate the work of C. W. Shaiffer, who prepared many of the figures in the report. Finally, we express our gratitude to D. Phillips, whose engaging pen-and-ink artwork graces this publication.

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