We conducted a 10‐year study (1998–2007) of the Mid‐Continent Population (MCP) of sandhill cranes (Grus canadensis) to identify spring‐migration corridors, locations of major stopovers, and migration chronology by crane breeding affiliation (western Alaska–Siberia [WA–S], northern Canada–Nunavut [NC–N], west‐central Canada–Alaska [WC–A], and east‐central Canada–Minnesota [EC–M]). In the Central Platte River Valley (CPRV) of Nebraska, we evaluated factors influencing staging chronology, food habits, fat storage, and habitat use of sandhill cranes. We compared our findings to results from the Platte River Ecology Study conducted during 1978–1980. We determined spring migration corridors used by the breeding affiliations (designated subpopulations for management purposes) by monitoring 169 cranes marked with platform transmitter terminals (PTTs). We also marked and monitored 456 cranes in the CPRV with very high frequency (VHF) transmitters to evaluate length and pattern of stay, habitat use, and movements. An estimated 42% and 58% of cranes staging in the CPRV were greater sandhill cranes (G. c. tabida) and lesser sandhill cranes (G. c. canadensis), and they stayed for an average of 20 and 25 days (2000–2007), respectively. Cranes from the WA–S, NC–N, WC–A, and EC–M affiliations spent an average of 72, 77, 52, and 53 days, respectively, in spring migration of which 28, 23, 24, and 18 days occurred in the CPRV. The majority of the WA–S subpopulation settled in the CPRV apparently because of inadequate habitat to support more birds upstream, although WA–S cranes accounted for >90% of birds staging in the North Platte River Valley. Crane staging duration in the CPRV was negatively correlated with arrival dates; 92% of cranes stayed >7 days. A program of annual mechanical removal of mature stands of woody growth and seedlings that began in the early 1980s primarily in the main channel of the Platte River has allowed distribution of crane roosts to remain relatively stable over the past 2 decades. Most cranes returned to nocturnal roost sites used in previous years. Corn residues dominated the diet of sandhill cranes in the CPRV, as in the 1970s, despite a marked decline in standing crop of corn residues. Only 14% (10 of 74) of PTT‐marked migrant cranes stayed at stopovers for ≥5 days before arriving in the CPRV, which limited the contribution of sites south of the CPRV for fat accumulation needed for migration and reproduction. Body masses of cranes (after adjusting for body size [an index of fat]) at arrival in the CPRV varied widely among years (1998–2006), indicating the importance of maintaining productive habitats on the wintering grounds to condition cranes for migration and reproduction. Average rates of fat gain by adult females while in the CPRV remained similar from 1978–1979 to 1998–1999 but declined among males. Distances cranes flew to feeding grounds in the CPRV increased as the percentage of cropland planted to soybeans increased and as density of cranes on nocturnal roosts increased. These results suggest that as habitats of limited or no value to cranes increase on the landscape, more flight time and higher maintenance costs may reduce fat storage. An estimated 40% of diurnal use occurred north of Interstate 80 (I‐80) where ≤5% of lands dedicated to crane conservation are located. Seventy‐four and 40% of PTT‐marked EC–M and WC–A cranes had spring migrations that included staging in eastern South Dakota for an average of 11 and 10 days, respectively. Cranes of the NC–N, WA–S, and WC–A subpopulations staged an average of 25, 17, and 12 days in central and western Saskatchewan/eastern Alberta. Females in these affiliations increased their fat reserves after leaving Nebraska by an estimated 450, 451, and 452 g, respectively, underscoring the key role of these staging areas in preparing the 3 subpopulations for reproduction. After departing Nebraska, MCP cranes roosted primarily in basin wetlands. Most of these wetlands are in private ownership and lack adequate protection, emphasizing the need for effective laws and policies to ensure their long‐term protection. The continued success of the current management goal of maintaining the MCP at approximately its current size and providing diverse recreational opportunities over a wide area of midcontinent and western North America is predicated on the ability of MCP cranes to continue to store large fat reserves in the CPRV in advance of breeding. For the CPRV to remain a key fat storage site, active channel maintenance (e.g., clearing of woody vegetation) likely will need to continue, along with establishing minimum stream flows. These actions would help ensure nocturnal roosting habitat remains sufficiently dispersed to provide cranes with daily intake of high‐energy food adequate for major fat storage and limit risk of high mortality from storms and disease. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

中文翻译：

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中洲沙丘鹤种群的春季迁徙生态，重点是内布拉斯加州中央普拉特河谷的使用

我们对沙丘鹤（Grus canadensis）的中洲种群（MCP）进行了为期十年的研究（1998-2007年）。）来确定春季迁徙的走廊，主要中途停留的地点以及按起重机育种隶属关系划分的迁徙年表（阿拉斯加西部–西伯利亚[WA–S]，加拿大北部–努纳武特[NC–N]，加拿大中西部–阿拉斯加[WC– A]，以及加拿大-明尼苏达州中东部[EC-M]）。在内布拉斯加州的中央普拉特河谷（CPRV）中，我们评估了影响分期年表，饮食习惯，脂肪储存和沙丘鹤栖息地使用的因素。我们将我们的发现与1978–1980年进行的普拉特河生态研究的结果进行了比较。我们通过监视169个标有平台发射器终端（PTT）的起重机，确定了育种单位（为管理目的指定的子种群）使用的春季迁徙走廊。我们还使用超高频（VHF）发射器标记并监控了CPRV中的456台起重机，以评估停留时间和格局，栖息地的使用和活动。在CPRV中，估计有42％和58％的起重机是较大的沙丘起重机（GC。tabida）和小沙丘鹤（G. c。canadensis），他们分别平均停留20天和25天（2000-2007年）。来自WA–S，NC–N，WC–A和EC–M隶属的起重机在春季迁徙中平均分别花费72、77、52和53天，其中28、23、24和18天为春季发生在CPRV中。显然，WA-S鹤的大部分种群居住在CPRV中，这是因为栖息地不足以支持上游的更多鸟类，尽管WA-S鹤占北普拉特河谷禽存栏的90％以上。CPRV中起重机的停留时间与到达日期呈负相关。92％的起重机停留超过7天。从1980年代初开始，主要在普拉特河的主要河道开始的年度机械清除成熟木本植物生长和幼苗计划，在过去的20年中使起重机栖息地的分布保持相对稳定。大多数起重机返回到前几年使用的夜间栖息地。与1970年代一样，在CPRV中，玉米残留物在沙丘鹤的饮食中占主导地位，尽管玉米残留物的现作收成明显下降。在到达CPRV之前，只有14％（74个中的10个）带有PTT标记的迁徙起重机在中途停留时间≥5天，这限制了CPRV南部站点对迁移和繁殖所需的脂肪积累的贡献。在到达CPRV时，起重机的体重（根据身体大小[脂肪指数]调整后）在几年之间（1998-2006年）变化很大，指出在越冬地上维持生产性栖息地以调节起重机迁徙和繁殖的重要性。在1978-1979年至1998-1999年期间，CPRV中成年女性的平均脂肪增加率保持相似，但男性中脂肪的下降率下降。随着种植在大豆中的农田比例的增加以及夜间栖息地上起重机密度的增加，起重机到CPRV的觅食地的距离也增加了。这些结果表明，随着起重机对栖息地价值的限制或没有价值的栖息地的增加，更多的飞行时间和更高的维护成本可能会减少脂肪的储存。估计有40％的日间使用量发生在80号州际公路（I-80）北部，其中≤5％的起重机专用土地位于该州。在PTT标记的EC–M和WC–A起重机中，有74％和40％的起重机进行了春季迁移，其中包括在南达科他州东部的平均迁移时间分别为11天和10天。在萨斯喀彻温省中部和西部/艾伯塔省东部，NC-N，WA-S和WC-A亚种群的起重机平均上演25、17和12天。这些隶属关系中的雌性离开内布拉斯加州后分别增加了450、451和452 g的脂肪储备，突显了这些分阶段区域在准备3个亚种群繁殖中的关键作用。离开内布拉斯加州后，MCP起重机主要栖息在流域湿地。这些湿地大多数是私人所有，缺乏适当的保护，强调需要有效的法律和政策来确保对其进行长期保护。当前管理目标的持续成功是将MCP起重机继续在CPRV中存储大量脂肪的能力为基础，该目标将MCP保持在目前的水平，并在北美中部和西部地区提供广泛的娱乐机会。繁殖前。为了使CPRV保持为主要的脂肪储存地点，可能需要继续进行主动渠道维护（例如清除木本植物），并确定最小的水流。这些行动将有助于确保夜间栖息地保持足够分散，从而为起重机提供每日摄入的高能量食物，足以储存大量脂肪，并限制暴风雨和疾病造成的高死亡率。2014年出版。本文是美国政府的著作，在美国属于公共领域。