Inferences regarding survival and recovery rates of winter-banded canvasbacks

Banding and recovery data from 3 populations of winter-banded canvasbacks (Aythya valisineria) were analyzed and survival and recovery rates were estimated. Sex-specific differences in these rates were detected in some populations, and lower survival rates were exhibited by females. Some geographic variation in survival rates was evident, suggesting that canvasbacks should not be managed strictly on a continent-wide basis. Evidence of temporal variation in both survival and recovery rates was found. Lower recovery rates were noted during periods of restrictive hunting regulations, but the relationship between survival rates and hunting regulations was not clear-cut. J. WILDL. MANAGE. 44(1):164-173 Recent concern for the apparent decline in the North American canvasback population (Trauger 1974) emphasizes the need for current estimates of production, survival, and recovery rates. The investigation of sources of variation in such parameter estimates is also especially important for populations thought to be declining. In this paper we present survival and recovery rate estimates obtained for 3 populations of winter-banded canvasbacks. Similar information on this species has been presented by Longwell and Stotts (1958), Geis (1959), DeGraff et al. (1961), and Geis and Crissey (1969). Motivation for the present analysis arose from the need to obtain current estimates of these parameters using recently-developed estimation models (e.g., Seber 1970, Robson and Youngs 1971, Brownie et al. 1978) that appear to be more appropriate than those used in the past (for rationale see Anderson and Burham 1976, Brownie et al. 1978, Burnham and Anderson 1979). We also tested several hypotheses concerning potential sources of variation in canvasback survival and recovery rates. Specifically, we examined sex-specificity of these rates as well as their geographic and temporal variation. Finally, we contrasted survival and recovery rates occurring during years of restrictive versus liberal hunting regulations. This analysis would have been impossible without the cooperation and efforts of individual banders. We acknowledge the efforts of all individuals who banded canvasbacks during winter from 1950 to the present. We acknowledge the assistance of the USFWS Bird Banding Laboratory in maintaining the banding and recovery records used in this analysis. Programming assistance was provided by R. Navitski, W. M. Cygan, J. E. Hines, and S. Rhoades. Technical assistance was provided by J. E. Hines, L. Moyer, M. Lare, and P. Bowley. Comments and criticisms of earlier drafts of the manuscript were provided by D. R. Anderson, F. W. Martin, H. F. Percival, M. C. Perry, and R. S. Pospahala. Editorial assistance was provided by D. Q. Thompson.