New Summer Areas and Mixing of Two Greater Sandhill Crane Populations in the Intermountain West

Population delineation, seasonal movement patterns, and habitat selection during annual life cycles of migratory birds are critical information needs to formulate regional and national management and conservation strategies. Historically, band recoveries, surveys, and resightings of marked individuals were used to delineate populations and migration routes and to estimate and assess habitat needs (Hestbeck et al. 1991; Anderson et al. 1992; Nichols et al. 1995; Williams 1997; Williams et al. 2008; Madsen et al. 2014). Recent technological advances in telemetry equipment (i.e., global positioning system (GPS) satellite platform transmitter terminals [PTTs]) have facilitated collection of geospatial data at multiple spatiotemporal scales. Such technology and associated data reduce constraints associated with very-high-frequency transmitters or mark–resight techniques (e.g., property access, personnel costs, and vehicle maintenance). In addition, PTTs are particularly useful for species that migrate long distances, such as greater sandhill cranes Grus canadensis tabida (hereafter crane), the largest (i.e., morphologically) migratory crane subspecies in North America (Drewein et al. 1976).

Cranes breed from the Great Lakes west to the Pacific Northwest and British Columbia (Drewien et al. 1976; Drewein and Lewis 1987; Pacific Flyway Council 1995). Breeding and winter distributions of cranes are used to define North American crane populations for management purposes. These populations are as follows: Eastern Population (EP), Rocky Mountain Population (RMP), Lower Colorado River Valley Population (LCRVP), Central Valley Population (CVP), Pacific Coast Population (PCP), and Mid-Continent Population (Figure 1). Life-history terms such as breeding, or summer areas, and nonbreeding, or winter areas, are often used interchangeably. However, we define summer areas as the final northern terminus following spring migration (usually during mid-March through mid-September) with inconclusive evidence cranes are paired, colts present, or nesting attempted. Breeding areas as concentrated areas within the summer area where the presence of breeding crane pairs, colts, or nesting have been confirmed. Typically, breeding occurs between May and August. Nonbreeding, or winter areas, are defined as the final southern terminus following fall migration (usually between early October and early March), and migration areas are defined as corridors between summer and winter areas.

Currently, three western crane populations are managed as unique, discrete units and therefore are managed differently (e.g., hunted vs. nonhunted). These westernmost crane populations (RMP, LCRVP, and CVP) summer and breed in the Intermountain West (Colorado, Idaho, Montana, Nevada, Oregon, Utah, Washington, and Wyoming); historic banding and survey data indicate these crane population have a wide geographic distribution (Drewien and Lewis 1987a; Littlefield et al. 1994; Pacific Flyway Council 1995). The RMP cranes summer and breed in central and eastern Idaho, western Montana, western Wyoming, northern and western Utah, and throughout mountain parks in western Colorado (Drewien and Bizeau 1974), and they spend winter (December–February) in the Middle Rio Grande Valley, New Mexico, southwestern New Mexico, southeastern Arizona, and northern Mexico (Pacific and Central Flyway Councils 2007).

Cranes in the LCRVP summer and breed in southwestern Idaho, northeastern Nevada, and northwestern Utah and are suspected to summer and potentially breed in south-central Idaho in the Cascade and Bear Valley–Stanley area(s) (Ivey et al. 2005; August 2011). They winter at Cibola National Wildlife Refuge (NWR), Colorado River Indian Reservation, Sonny Bono Salton Sea NWR, and near the town of Brawley, California (Pacific Flyway Council 1995). The CVP cranes summer and breed in southeastern and south-central Oregon, the Oregon Cascades, and southern Washington (Littlefield et al. 1994), and they winter entirely in the Central Valley of California (Littlefield and Thompson 1979; Pacific Flyway Council 1997). Range boundaries of these populations, delineated with existing banding and survey data, remain poorly defined and are complicated by the presence of unmarked cranes within the three populations that converge in northeastern Nevada, southeastern Oregon, southwestern Idaho, and northwestern Utah (Drewien et al. 2000).

In addition, RMP cranes are legally hunted annually in areas where LCRVP cranes may congregate on fall migration areas in eastern Idaho, northern Utah, southwestern Montana, and western Wyoming (Pacific and Central Flyway Councils 2007). There was an approved hunt (U.S.D.I. 2007) for LCRVP cranes in Arizona, but the approved hunt was only implemented once (as a youth hunt) in the three possible years it was approved (2010), and it is unknown whether LCRVP cranes are harvested during approved RMP hunting seasons. In addition, lack of banded birds to allow for population identification and logistical constraints (e.g., isolated wetlands, private lands access, and remote backcountry) have previously limited the ability to identify connectivity and origins of cranes that summer and intermingle in the areas described above. Therefore, our objectives were to 1) use GPS PTTs to identify yet-to-be-determined summer areas for the LCRVP of cranes and 2) determine whether intermingling occurs among any of the western crane populations (RMP, LCRVP, and CVP) during summer and on fall migration areas in the Intermountain West.

We studied cranes on Cibola NWR (33.31°N, 114.69°W) that encompasses 6,988 ha of land in La Paz County, Arizona, and Imperial County, California. Cibola NWR is located on the main branch of the lower Colorado River. Vegetation is comprised of narrow fragmented strips of riparian vegetation dominated by native and nonnative species (Tamarix spp.) adjacent to the river corridor, surrounded by Sonoran Desert upland and a variety of rotating agricultural fields (Paxton et al. 2008).

We studied cranes on Sonny Bono Salton Sea NWR (33.15°N, 115.73°W) that encompasses 13,259 ha in Imperial County, California, and near Brawley, California (32.58°N, 115.31°W) within the Imperial Valley of California. The entire Imperial Valley, including Sonny Bono Salton Sea NWR, is surrounded by Sonoran Desert uplands. The NWR consisting of the Salton Sea, some managed wetland units, and a variety of rotating agricultural fields within a system of concrete water-delivery ditches and canals and earthen drains (Rosenberg and Haley 2004; LaFever et al. 2008).

We studied cranes in Long Valley, Idaho (44.52°N, 116.05°W), located in west-central Idaho approximately 100 km north of Boise. The area is a broad, flat, glaciated valley dominated by agricultural grasslands, and dense riparian stands of lodgepole pine Pinus contorta. Surrounding the valley are mountain ranges consisting of Ponderosa pine Pinus ponderosa, grand fir Abies grandis, and Douglas fir Pseudotsuga menziesii (Van Daele and Van Daele 1982).

We used rocket nets and noose snares to capture cranes at Cibola NWR and Sonny Bono Salton Sea NWR during January and February 2014 and January 2015 (Wheeler and Lewis 1972; Urbanek et al. 1991; Hereford et al. 2001). We used dip nets to capture colts before flight capability in south-central Idaho in July 2014. We used plumage characteristics to identify adult cranes (i.e., a crane known to have hatched before the calendar year of banding with well-developed pale cheek and red skin on their crown) and colts (i.e., a crane capable of sustained flight and known to have hatched during the calendar year in which banded with an undeveloped pale cheek and red crown; Lewis 1979; Krapu et al. 2011). A 22-g solar-powered PTT was mounted to a two-piece leg band with one-half engraved with a unique alphanumeric code. We attached the leg bands mounted with the PTTs to individual cranes (Microwave Telemetry, Inc. Columbia, MD; Ivey et al. 2005; Krapu et al. 2011). Each PTT was programmed by the manufacturer to record four GPS locations per day (Microwave Telemetry, Inc.; for a complete description of the ARGOS system, see Fancy et al. 1988; Harris et al. 1990). In addition, we attached a standard size 9 U.S. Geological Survey Bird Banding Laboratory band on the right tibia above the tibio-tarsus on all captured cranes (Krapu et al. 2011). All capture and handling methods were approved by the Texas Tech University Institutional Animal Care and Use protocol 13108-12.

We captured 43 cranes (n = 25 Cibola NWR, n = 12 Imperial Valley, n = 2 Sonny Bono Salton Sea NWR, n = 4 south-central Idaho) and deployed 16 PTTs (n = 10 Cibola NWR, n = 1 Sonny Bono Salton Sea NWR, n = 5 Imperial Valley) in January 2014. In addition, we captured cranes and deployed PTTs (n = 4 south-central Idaho) in July 2014 and one PTT (n = 1 Sonny Bono Salton Sea NWR) in January 2015. We captured 38 adult cranes and five colts; of which four colts were captured during summer 2014 (Figure 2). One of the PTTs from the original 17 malfunctioned and it was excluded from analyses.

Nine of 17 cranes (52.9%) marked with PTTs and captured on Sonny Bono and Cibola NWRs settled in previously defined LCRVP breeding areas, whereas four cranes marked on Cibola NWR settled on the Idaho–Nevada border on the Duck Valley Indian Reservation on the fringe of traditional LCRVP breeding areas (Figure 3). The other three cranes settled in areas north of Boise considered outside of the LCRV crane breeding area (Figure 4). One crane marked on Cibola NWR settled around Indian Valley near Cambridge, Idaho, however, the PTT failed after 30 April 2014. We speculate this is a summer area because we observed unmarked cranes while we were searching for the marked bird after its last successful transmission (April 2014). The other crane marked at Cibola NWR settled near Donnelly and spent the summer (2014) in this area before returning back to the lower Colorado River Valley in Arizona. In addition, one crane marked on Sonny Bono Salton Sea NWR January 2015 was in the southern portion of Long Valley near Cascade as of June 2015. Four flightless colts were captured in July 2014 near New Meadows, Donnelly, Bear Valley, and Hill City, Idaho, respectively. We chose Donnelly for capture because 1) a marked LCRVP bird was consistently present there after 30 March 2014 to 1 September 2014, 2) the New Meadows and Bear Valley areas were suspected of being in the LCRVP summer, and 3) the Hill City area was an exploratory attempt to determine where birds in the area winter (LCRVP vs. RMP winter areas).

Only the marked colt from Donnelly survived to migration (Figure 5). Surprisingly, this colt, which fledged from an area where there was a marked LCRVP crane, did not migrate to the traditional LCRVP wintering area. Instead, this colt, assumed to be with adult cranes, migrated through southeastern Idaho (Malad Valley, Idaho), northeastern Utah, and south-central Utah, respectively (Bear River Migratory Bird Refuge, Richland, Utah), and then to the Middle Rio Grande Valley of New Mexico. The Middle Rio Grande Valley of New Mexico supports >80% of wintering cranes of the RMP (Pacific and Central Flyway Councils 2007). This marked crane was observed visually with its family group at its winter terminus in the Middle Rio Grande Valley of New Mexico. During spring migration (2015), the colt moved through the San Luis Valley of Colorado, considered a major fall and spring area for RMP cranes (Figure 6), and has made its way back to the Cascade Reservoir, Idaho, as of 29 March 2015 after a brief stop around Bear River Migratory Bird Refuge. As per historical population designations, this bird would be considered an RMP crane (Table 1).

Our study suggests LCRVP summer in areas outside of what has been considered their traditional summer area and suggests intermixing of LCRV and RMP. The summer distribution of LCRVP cranes has been well documented on the traditional breeding areas of Nevada via summer counts (Pacific Flyway Council 1995; August 2011). The LCRVP, however, was hypothesized to be expanding their summer area into Idaho (C. Littlefield and R. Drewien, personal communications; Pacific Flyway Council 1995). It is possible that use of these areas by LCRV birds has simply been undocumented in the past, but we believe it more plausible that this population is expanding into new areas given recent population increases (Kruse et al. 2014).

Although the summer distribution of cranes of the RMP is well documented from eastern to central Idaho, it is poorly defined on the western boundary and complicated by the presence of cranes associated with the CVP and LCRVP (Drewien et al. 2000). A long-term marking program by Drewien et al. (2000) found no recoveries or sightings of marked cranes of the CVP (Littlefield et al. 1994) within the range of RMP or vice versa. This is surprising given that only 200−225 km separates the known western RMP summer areas in the Camas Prairie and Stanley Basin of south-central Idaho from CVP summer areas in the Jordan Valley in southeastern Oregon (Littlefield et al. 1994; Drewien et al. 2000). Likewise, Drewien et al. (2000) did not obtain any recoveries of RMP or CVP within the range of the LCRVP. In contrast, Rawlings (1992) previously confirmed overlap between RMP and LCRVP around Lund, Nevada, a location at the southern terminus of the previously established traditional summer area for LCRVP that serves as a spring migration area. Historic recovery data and long-term marking studies (Drewien and Bizeau 1974; Drewien et al. 1987a, 1987b, 1996, 1999; Manes et al. 1992) indicate the RMP is a discrete biological entity with distinct breeding areas separate from the other Intermountain West populations. Location data from the marked colt near Donnelly, however, provides the first piece of evidence the LCRVP and RMP have overlapping summer areas. Considering <300 km separates summer areas for these populations, our findings warrant additional delineation of summer areas for the CVP, LCRVP, and RMP and demonstrate the efficacy of the use of satellite transmitters to acquire otherwise unattainable data.

Currently, three western crane populations are managed as discrete units and therefore are managed separately as discrete units (e.g., hunted vs. nonhunted). Our data suggest continued management of the three populations without careful delineation of summer and migration areas may have negative impacts (e.g., harvest pressure, critical habitat loss, and redistribution to suboptimal habitat) to the populations. Conservation and management of the three populations would benefit by assessing the extent of the summer and migration area overlap and determine whether any overlap is 1) the result of population expansion; 2) simply due to lack of documentation; or 3) for example, due to the lack or decline in availability in quality of breeding or migration areas across the Intermountain West. A simultaneous effort to intensively mark and band all three western crane populations could answer these questions. If done simultaneously, at relevant spatiotemporal scales, more accurate and geospatially explicit population boundaries may be defined that will inform harvest management and serve to provide better population monitoring and assessment of all three crane populations.

Please note: The Journal of Fish and Wildlife Management is not responsible for the content or functionality of any supplemental material. Queries should be directed to the corresponding author for the article.

Data S1. Data used for creation of maps within ArcGIS 10 of specific sandhill crane Grus canadensis locations during 2014–2015. Data are contained within individual tabs with column abbreviations explained in the TXT source file.

Found at DOI: http://dx.doi.org/10.3996/042015-JFWM-036.S1 (1 KB TXT).

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We thank Gary Ivey with the International Crane Foundation and U.S. Fish and Wildlife Service (USFWS) Refuge staff (Bosque del Apache, Cibola, and Sonny Bono Salton Sea NWRs) Tom Anderson, Stephanie Goehring, Jamison Grzyb, Steven Rimer, Ryan Woody, John Vradenburg, and Brenda Zaun for field and logistical support. We thank Idaho Department of Fish and Game staff Regan Berkley, Bill Bosworth, Diane Evans-Mack, and Craig White for field and logistical assistance. We thank the Associate Editor and three reviewers for the time spent reviewing this manuscript. This is manuscript T-9-1270 of the College of Agricultural Sciences and Natural Resources, Texas Tech University.

Financial and logistical support for this research was provided by the USFWS Webless Migratory Game Bird program and Texas Tech University.

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.