Ecology and Management of Avian Botulism on the Canadian Prairies

61INTRODUCTION<strong>Avian</strong> botulism (Clostridium botulinum, Type C) is an issue <strong>of</strong> major concern to waterfowlmanagers in North America, in part because the frequency <strong>and</strong> magnitude <strong>of</strong> botulism outbreakshas increased in recent years. Although catastrophic losses <strong>of</strong> waterfowl to botulism are welldocumented, little is known about the impact <strong>of</strong> the disease at the population level. In particular,estimates <strong>of</strong> botulism-related mortality rates are lacking, as the number <strong>of</strong> individuals present atoutbreak sites (i.e., number at risk) is rarely quantified.Our first aim was to use b<strong>and</strong>-recovery data from mallards (Anas platyrhynchos) trapped at ninemajor outbreak sites in Prairie Canada, to test the hypothesis that individuals exposed to outbreaklevels <strong>of</strong> botulism during the post-breeding season suffer reduced late-summer survival as aconsequence. Specifically, we tested the prediction that direct recovery rates (indicative <strong>of</strong>survival between b<strong>and</strong>ing <strong>and</strong> the hunting season) would be lower among individuals b<strong>and</strong>ed atoutbreak sites than among conspecific individuals b<strong>and</strong>ed at non-outbreak control sites.We also summarize results <strong>of</strong> an analysis aimed at assessing the extent to which carcass removalis effective in reducing mortality among post-breeding mallards. Specifically, using b<strong>and</strong>ingdata assembled from a three-year field investigation, we tested the prediction that the rate <strong>of</strong>direct recovery by hunters (indicative <strong>of</strong> survival during the period between b<strong>and</strong>ing <strong>and</strong> harvest)should be higher among birds b<strong>and</strong>ed at outbreak sites with intensive clean-up operations thanamong birds b<strong>and</strong>ed at outbreak sites with no such clean-up. This second direct recoveryanalysis complements that shown in Part II <strong>of</strong> this report.METHODSData collectionThis study was conducted as part <strong>of</strong> a broader investigation, initiated in 1998 by the PrairieHabitat Joint Venture (PHJV) <strong>Avian</strong> <strong>Botulism</strong> Working Group. Field protocols for that broaderinvestigation included the capture <strong>and</strong> b<strong>and</strong>ing <strong>of</strong> mallards <strong>and</strong> other dabbling ducks at selectedbotulism outbreak sites in each <strong>of</strong> the three Canadian Prairie provinces. B<strong>and</strong>ing data used in theanalyses presented here were derived from fieldwork conducted at the following botulismoutbreak sites: Pakowki Lake, Alberta (AB) <strong>and</strong> Old Wives Lake, Saskatchewan (SK) in 1998;Kimiwan Lake, AB, Eyebrow Lake, SK, Old Wives Lake, SK, <strong>and</strong> Whitewater Lake, AB in1999; <strong>and</strong> Frank Lake, AB, Crane Lake, SK, Paysen Lake, SK, Kettlehut Lake, SK, <strong>and</strong>Whitewater Lake, Manitoba (MB) in 2000 (locations <strong>and</strong> coordinates <strong>of</strong> lakes are shown inFigure 1 <strong>and</strong> Table 1 <strong>of</strong> the General Introduction). In each <strong>of</strong> the three years, a subset <strong>of</strong>outbreak sites was subjected to surveillance <strong>and</strong> carcass collection as part <strong>of</strong> an experimentalprotocol aimed at assessing the effectiveness <strong>of</strong> traditional management practices. Additionalb<strong>and</strong>ing information was obtained from “control” wetl<strong>and</strong>s that lacked botulism outbreaks(details below).