Population delineation throughout the annual life cycle for migratory birds is needed to formulate regional and national management and conservation strategies. Despite being well studied continentally, connectivity of sandhill crane Grus canadensis populations throughout the western portion of their North American range remains poorly described. Our objectives were to 1) use global positioning system satellite transmitter terminals to identify summer distributions for the Lower Colorado River Valley Population of greater sandhill cranes Grus canadensis tabida and 2) determine whether intermingling occurs among any of the western greater sandhill crane populations: Rocky Mountain Population, Lower Colorado River Valley Population, and Central Valley Population. Capture and marking occurred during winter and summer on private lands in California and Idaho as well as on two National Wildlife Refuges: Cibola and Sonny Bono Salton Sea National Wildlife Refuges. A majority of marked greater sandhill cranes summered in what is established Lower Colorado River Valley Population breeding areas in northeastern Nevada and southwestern Idaho. A handful of greater sandhill cranes summered outside of traditional breeding areas in west-central Idaho around Cascade Reservoir near Donnelly and Cascade, Idaho. For example, a greater sandhill crane colt captured near Donnelly in July 2014 survived to winter migration and moved south to areas associated with the Rocky Mountain Population. The integration of the greater sandhill crane colt captured near Donnelly provides the first evidence of potential intermingling between the Lower Colorado River Population and Rocky Mountain Population. We suggest continued marking and banding efforts of all three western populations of greater sandhill cranes will accurately delineate population boundaries and connectivity and inform management decisions for the three populations.
Cranes (Antigone canadensis) use an array of migratory strategies, ranging from "jumping," or taking 1 or 2 flights from wintering grounds to a staging area, then on to the breeding grounds, to "hopping," or taking shorter flights among multiple (>3) staging areas between termini. We captured 16 adult and 2 juvenile Greater Sandhill Cranes (Antigone canadensis tabida) from the Lower Colorado River Valley population (LCRVP) and fitted them with platform transmitter terminals (PTTs) for GPS satellite telemetry. We used recorded locations and Brownian bridge movement models (BBMMs) to identify migration corridors and areas of migratory use (AMUs) during spring and fall migration (2014)(2015)(2016). Eighty-nine percent of our sample (n = 16) of LCRVP Sandhill Cranes with PTTs flew direct paths between summer and winter termini. Starting in the Great Basin and moving into the Mojave Desert and then into the Sonoran Desert, the LCRVP aligned its migration with drainages, rivers, and reservoirs. Within those direct paths, we identified 18 unique and discrete AMUs along an ∼1000-km corridor and 3 within minor corridors taken by the other 2 cranes. We defined AMU as an area within a crane's 75% BBMM migration confidence contour where the crane had 2 or more subsequent time stamps (could be ≥3 hours) and did not travel >40 km from the first time stamp. The average migration duration was 23 days (spring, n = 3; fall, n = 2; cranes, n = 53). The fact that many individuals stopped several times after relatively short flights during both migration seasons suggests that the LCRVP generally uses a "hop" migration strategy. The use, often frequent and consecutive, of the 21 AMUs in this research reveals the potential importance of these migration areas to the LCRVP for its social, behavioral, and energetic requirements during migration. Détermination de la stratégie de migration adoptée par les Grandes Grues du Canada appartenant à la population de la vallée du Colorado inférieurRÉSUMÉ. En Amérique du Nord, la Grue du Canada (Antigone canadensis) a recourt à diverses stratégies de migration, allant des « grands sauts », c'est-à-dire d'effectuer un ou deux vols de l'aire d'hivernage à une halte printanière pour ensuite se rendre à l'aire de nidification, aux « petits bonds », soit d'entreprendre des vols plus courts entre plusieurs haltes (>3) jusqu'à la destination finale. Nous avons capturé 16 adultes et 2 jeunes Grandes Grues du Canada (Antigone canadensis tabida) appartenant à la population de la vallée du Colorado inférieur (PVCI) et les avons munis d'une balise radio avec télémétrie satellitaire GPS. Nous avons utilisé les positions enregistrées et des modèles de déplacement fondés sur le pont brownien (MDPB) pour déterminer les corridors de migration et les secteurs utilisés en migration (SUM) printanière et automnale (2014)(2015)(2016). Quatre-vingt-neuf pourcent de notre échantillon (n = 16) de grues équipées de balise ont parcouru des trajets directs de leur aire de nidification à leur aire d'hivernage. Au départ du Gran...
Identifying habitat selection and use is important to understand in wildlife management because it informs habitat manipulations, conservation efforts, and species distribution. Habitat selection by sandhill cranes (Antigone canadensis) has been studied primarily on overwintering areas and a few summering locations. Summer habitat selection by the Lower Colorado River Valley Population of greater sandhill cranes (A. c. tabida) in the Intermountain West is not widely known, but has been identified as an information need by many wildlife management agencies. We captured and attached satellite platform transmitter terminals to 21 adult sandhill cranes on Cibola and Sonny Bono Salton Sea National Wildlife Refuges in Arizona and California, and private lands in California and Idaho. Home ranges of all marked cranes (50% core area: x̄ = 525.4 ha, SE = 155.6; 99% isopleth: x̄ = 6,476.5 ha, SE = 1,637.5) were similar to other studies on summering grounds. Resource analysis indicated that marked sandhill cranes used wetland habitats in greater proportion than their availability for both nocturnal and diurnal locations at the population level, by individuals within the entire landscape, and by individuals within their core area. Wetland habitats consist of ∼7% of the available habitat. Within the Wetland category, the Temperate Flooded and Swamp Forest level (a Formation level in the National Vegetation Classification system) was the most important to summering Lower Colorado River Population sandhill cranes. Wetland managers can concentrate their efforts for conservation, enhancement, and restoration on these type of wetlands to ensure the sustainability of this small population of sandhill cranes.
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