Changes in the number and distribution of Greater Sandhill Cranes in the Eastern Population

Once nearly extirpated, the Eastern Population (EP) of Greater Sandhill Cranes (Grus canadensis tabida) has increased in number and expanded its range in breeding and wintering areas. Data from Christmas Bird Counts (CBCs) and Breeding Bird Surveys (BBSs) were used to delineate changes in the wintering and breeding area distributions during the period from 1966 to 2013. Crane densities were plotted to the centroid of CBC circles or BBS routes, and the Geographic Mean Centers (GMCs) for wintering and breeding populations were calculated. The number of Greater Sandhill Cranes detected during the breeding season has steadily increased since 1966, with just six birds observed in 1966 and 1046 observed in 2013. The GMC of the Sandhill Crane breeding population has remained in Wisconsin during the 47-yr time frame. The total number of Sandhill Cranes counted in the eastern United States during CBCs grew from 423 in 1965–1966 to 46,194 in 2012–2013, with a peak number of 55,826 in 2011–2012. The GMC of wintering Greater Sandhill Cranes was located in Florida during the periods from 1966 to 1977 and 1978 to 1989, but shifted north-northwest by nearly 4° of latitude (into Georgia) by 1990–2001. By 2002–2013, the GMC had shifted an additional degree north as well as almost a degree west in longitude. Greater Sandhill Cranes in the EP may continue to winter further north and remain in more northerly areas later in the fall before migrating further south. Factors such as annual weather, long-term climate change, and changes in land use may influence future population trends and changes in both the breeding and wintering ranges of the EP of Sandhill Cranes. Una vez casi extirpada, la población de Grus canadensis tabida del oriente, ha incrementado en numero y expandido su rango en área de reproducción e invernales. Datos de Conteos Navideños (CN) y Censos de Aves Reproductivas (CAR) fueron utilizados para delinear cambios en la distribución en el área de invernal y reproductiva durante el periodo desde 1996 hasta 2013. Las densidades de las Grulla fueron graficada al centroide de los círculos de CN y las rutas CAR y fueron calculados los Centros Geográficos Promedio (CGP) para las poblaciones invernales y reproductivas. El numero de G. c. tabida detectados durante la temporada reproductiva ha incrementado sostenidamente desde 1996, con solo seis aves observadas en 1996 y 1046 observadas en el 2013. Los CGP de las poblaciones de G. c. tabida han permanecido en Wisconsin