Assignment and quantification of breeding production areas of migratory birds is a crucial step in understanding their population dynamics and informing conservation and management decisions, especially for game birds. Sandhill Cranes (Grus canadensis) breed throughout the North American boreal, taiga, and non-forested regions of the Arctic and Siberia. Birds harvested in North America originate from these remote northern regions but conventional mark-recapture techniques cannot readily be used to answer key questions of proportionate take due to the logistical impossibility of marking young birds in an unbiased way. We used stable-hydrogen isotope analyses (δD) of feathers from 242 hatch-year (HY) and 628 after-hatch year (AHY) cranes harvested during the 2002 and 2003 hunting seasons in Saskatchewan, North Dakota, Kansas, Oklahoma, and Texas in order to provide new quantitative information regarding their geographical origins. While adult cranes originated from throughout the breeding range, south of the tree line, most birds were produced in the southeast boreal of western Ontario and/or central Manitoba and/or western Alaska. Adult birds taken in Saskatchewan, at the northern portion of the collection area, showed more northwesterly origins than birds taken at the southernmost extreme in Texas. Isotopic analysis of claws and feathers from individuals showed good correlation suggesting that claws could also be used to delineate latitude of origin, especially for AHY birds that may retain some flight feathers for more than one year. Future studies need to consider more carefully the potential contributions of southern boreal populations and if possible to develop means to distinguish isotopically those birds originating in western Alaska.
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Vol. 29 • No. 2