Demographics of the Gulf Coast Subpopulation of Mid-continent Sandhill Cranes

Current recommendations for subpopulation management for mid-continent sandhill cranes (Grus canadensis) are based on tentative evidence that suggests geographic separation of crane concentrations during migration and winter and possible variation in demographic characteristics between these groups. We determined distribution, abundance, subspecific composition, and annual recruitment of the Gulf Coast subpopulation of mid-continent sandhill cranes because little information was available on most demographic characteristics of this subpopulation. Based on aerial line transect surveys conducted along the Texas Coast during winter, subpopulation abundance was 120,072 cranes (SD = 31,845) during 1996-1997 and 121,057 cranes (SD = 31,521) during 1997-1998. Winter age ratios (percent hatch-year cranes) along the Texas Gulf Coast ranged from 9.5% (SE=0.52, N=3,239 cranes) to 10.8% (SE=0.61, N=2,570 cranes), indicating that annual recruitment was lower than previously reported. Subspecific composition of cranes wintering along the Texas Coast included 28%-32% greater sandhill cranes (G. c. tabida), 62%-68% Canadian sandhill cranes (G. c. rowani), and 4%-8% lesser sandhill cranes (G. c. canadensis) during the winters of 1995-1997. Few greater sandhill cranes were present in either the Rolling Plains or South Texas Plains during the hunting season. A subpopulation boundary through these regions would include the majority of greater sandhill cranes in the Gulf Coast subpopulation.

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