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Résumé :
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Focusing conservation strategies requires identifying the demographic parameters and environmental conditions affecting the growth of animal populations most. Therefore, we examined relationships between population demographics and winter drought (1950-2011) for endangered whooping cranes (Grus americana) wintering in Texas, USA. We modeled winter loss and its contribution to annual mortality as functions of winter drought, determined recruitment needed to maintain population growth after drought, and identified which demographic parameters underpin this population's growth. Previous research assumed winter loss (i.e., birds missed in subsequent surveys) represented mortality. We show that loss includes temporary emigration to upland habitats, early migration, and incomplete detection. Despite this, we maintained this assumption to evaluate the relevance of winter mortality to population growth. We found that winter loss ((beta) over cap = 0.308, SE = 0.042) and its contribution to annual mortality ((beta) over cap = 0.318, SE = 0.047) increased with drought severity (Palmer hydrological drought index; PHDI). Given average recruitment (0.145, SD = 0.090), this population increases 1.2% (95% Cl = -2.9% to 4.2%) after extreme drought (PHDI = 4). No recruitment must occur for 3 years with moderate to severe drought (PHDI
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