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Tuesday, February 7 • 9:40am - 10:00am
Technical Session. Modeling Transition Rates of Sandhill Cranes Using a Multi-state Model and Estimating Population Trends with N-mixture Models

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AUTHORS: Mike Wheeler, Tim Van Deelen - University of Wisconsin, Madison; Jeb Barzen, International Crane Foundation

ABSTRACT: Long-term trends in Midwestern sandhill crane populations indicate positive growth despite much yearly variability, and continued monitoring will be required for effective management. This study is being conducted to explore relationships between life-history stage and recruitment in sandhill crane populations, as well as to estimate the size of the study population. Since 1990, the International Crane Foundation (Baraboo, Wisconsin) has collected long-term re-sightings data on territorial and non-territorial sandhill cranes in southcentral Wisconsin. We used these data in a multi-state model to estimate survival and state-transition probabilities of different demographic groups. Primary sessions were on an annual basis, with observations being recorded during the breeding and chick rearing seasons. State variables were Territorial and Non-territorial, and classifying birds in either category was based on behaviors observed during re-sightings. Results suggest high annual survival rates (~90%) and low annual rates of territory acquisition or loss (~5%). N-mixture models were used to estimate population size with visual observation data independent of the mark-resight models. With estimates of population trends through time, we calibrated our matrix model to produce more realistic estimates of recruitment. Preliminary results suggest that survival of territorial adults and their continued tenure on territory have appreciable effects on growth rate – hence availability of suitable territories may regulate growth rates. Consequently, management of crane populations in the Midwest may depend on creating habitats that support territory establishment.

Tuesday February 7, 2017 9:40am - 10:00am CST
Grand Ballroom D