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Sandhill cranes (Antigone canadensis) inhabiting the midcontinent of North America have been hunted since the 1960s under management goals of maintaining abundance, retaining geographic distribution, and maximizing sustainable harvest. Some biologists have raised concerns regarding harvest sustainability because sandhill cranes have lower reproductive rates than other game birds. We summarized demographic information in an age‐structured matrix model to better understand population dynamics and harvest. Population indices and recovered harvest since the early 1980s suggest midcontinent sandhill cranes have experienced an average long‐term annual growth of 0.9%; meanwhile, harvest has increased 1.8% annually. Adult survival and recruitment rates estimated from field data required modest adjustments (1–3%) so that model‐derived growth rates matched growth estimated from a long‐term survey (0.887 adult survival and 0.199 females/breeding female). Considering 0.9% long‐term annual growth, sandhill cranes could be harvested at a rate of 6.6% if harvest was additive to natural mortality (assumed to be 0.05) or 11.3% if harvest mortality compensated for natural mortality. Life‐history characteristics for long‐lived organisms and demographic evidence suggested that hunter harvest was primarily additive. Differential harvest rates of segments of sandhill cranes in the midcontinent population derived from differential exposure to hunting suggested potentially unsustainable harvest for greater sandhill cranes (A. c. tabida) from 2 breeding segments. Overall, demographic evidence suggests that the harvest of sandhill cranes in the midcontinent population has been managed sustainably. Monitoring activities that reduce nuisance variation and estimate vital and harvest rates by subspecies would support continued management of sandhill cranes that are of interest to hunters and bird watchers. Published 2020. This article is a U.S. Government work and is in the public domain in the USA. Long‐term survey estimates and population model results suggest that harvest of sandhill cranes from the midcontinent population has been implemented sustainably. Managing this population as a single entity involves potential risks to specific groups of sandhill cranes; therefore, improved monitoring activities that reduce nuisance variation and estimate vital and harvest rates would support continued management.

Sites used for roosting represent a key habitat requirement for many species of birds because availability and quality of roost sites can influence individual fitness. Birds select roost sites based on numerous factors, requirements, and motivations, and selection of roosts can be dynamic in time and space because of various ecological and environmental influences. For sandhill cranes (Antigone canadensis) at their main spring‐staging area along the Platte River in south‐central Nebraska, USA, past investigations of roosting cranes focused on physical channel characteristics related to perceived security as motivating roost distribution. We used 6,310 roost sites selected by 313 sandhill cranes over 5 spring migration seasons (2003–2007) to quantify resource selection functions of roost sites on the central Platte River using a discrete choice analysis. Sandhill cranes generally showed stronger selection for wider channels with shorter bank vegetation situated farther from potential human disturbance features such as roads, bridges, and dwellings. Furthermore, selection for roost sites with preferable physical characteristics (wide channels with short bank vegetation) was more resilient to nearby disturbance features than more narrow channels with taller bank vegetation. The amount of cornfields surrounding sandhill crane roost sites positively influenced relative probability of use but only for more narrow channels <100 m and those with shorter bank vegetation. We confirmed key resource features that sandhill cranes selected at river channels along the Platte River, and after incorporating spatial variation due to human disturbance, our understanding of roost site selection was more robust, providing insights on how disturbance may interact with physical habitat features. Managers can use information on roost‐site selection when developing plans to increase probability of crane use at existing roost sites and to identify new areas for potential use if existing sites become limited. © 2016 The Wildlife Society. Sandhill cranes selected roost sites along the Platte River that had wider channel widths, lower bank vegetation height, were farther from human disturbance, and had more cornfields in close proximity. Managers can use this information to increase probability of crane use at existing roost sites and to develop new areas for potential use if existing sites become limited.

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. Llevamos a cabo un estudio de 10 años (1998–2007) de la Población Centro‐Continental (MCP) de grulla canadiense (Grus canadensis) para identificar los corredores utilizados durante la migración de primavera, la localización de los principales sitios de parada migratoria y la cronología de migración por afiliación reproductiva (oeste de Alaska–Siberia [WA–S], norte de Canadá–Nunavut [NC–N], centro oeste de Canadá–Alaska [WC–A] y centro este de Canadá–Minnesota [EC–M]). En el Valle del Central Platte River (CPRV) de Nebraska, evaluamos los factores que influencian la cronología de los sitios de escala, los hábitos alimenticios, las reservas de grasa corporal y el uso del hábitat de las grullas canadienses. Comparamos nuestros hallazgos con los resultados del estudio de ecología del Platte River llevado a cabo durante 1978–1980. Determinamos los corredores utilizados durante la migración de primavera por las afiliaciones reproductivas (designadas subpoblaciones para el propósito de manejo) monitoreando 169 grullas marcadas con transmisores PTT (platform transmitter terminal). También marcamos y monitoreamos 456 grullas en el CPRV con transmisores very high frequency (VHF) para evaluar la duración y el patrón de estancia, el uso del hábitat y los movimientos. Se estima que el 42% y el 58% de las grullas que hicieron escala en el CPRV eran grullas canadienses mayores (G. c. tabida) y grullas canadienses menores (G. c. canadensis), y que se mantuvieron en el área un promedio de 20 y 25 días (2000–2007), respectivamente. Las grullas de las afiliaciones WA–S, NC–N, WC–A, y EC–M estuvieron un promedio de 72, 77, 52, y 53 días migrando durante la primavera, respectivamente, de los cuales 28, 23, 24, y 18 días ocurrieron en el CPRV, respectivamente. La mayoría de la subpoblación WA–S se instaló en el CPRV, debido aparentemente al insuficiente hábitat para mantener más aves río arriba, si bien las grullas de la WA–S representaron >90% de las aves que hicieron escala en el valle del North Platte River. La duración de la escala de las grullas en el CPRV se correlacionó negativamente con la fecha de llegada; el 92% de las grullas se quedaron >7 días. Un programa anual de remoción mecánica de árboles maduros y plántulas que empezó a principios de los años 80 ante todo en el canal principal del Platte River, ha permitido que la distribución de dormideros de grullas se mantenga relativamente estable durante las 2 últimas décadas. La mayoría de las grullas regresaron a los dormideros nocturnos utilizados en años anteriores. El maíz residual dominó la dieta de las grullas canadienses en el CPRV, al igual que en los años 70, a pesar de una disminución marcada del desecho residual de maíz posterior a la cosecha. Solamente el 14% (10 de 74) de las grullas marcadas con transmisores PTT se quedaron en los sitios de parada migratoria durante ≥5 días antes de llegar al CPRV, lo cual limitó la contribución de los sitios al sur del CPRV a la acumulación de la grasa corporal necesaria para la migración y la reproducción. Las masas corporales de las grullas (después de compensar por el tamaño del cuerpo [un índice de grasa corporal]) a la llegada al CPRV variaron ampliamente entre años (1998–2006), indicando la importancia de mantener hábitats productivos en las áreas de invernada para preparar a las grullas para la migración y la reproducción. El promedio de grasa corporal ganada por hembras adultas durante su estancia en el CPRV permaneció similar desde 1978–1979 hasta 1998–1999, pero disminuyó en los machos. Las distancias que las grullas volaron hasta las áreas de alimentación en el CPRV aumentaron a medida que el porcentaje de soya plantada y la densidad de grullas en los dormideros nocturnos aumentaron. Estos resultados sugieren que a medida que los hábitats con un valor reducido o nulo para las grullas aumentan en el paisaje, el aumento de la duración del vuelo y costo de mantenimiento pueden reducir las reservas de grasa corporal. Se estima que el 40% del uso diurno ocurrió al norte de la autopista interestatal 80 (I‐80) donde se localizan ≤5% de los terrenos dedicados a la conservación de grullas. Setenta y cuatro y 40% de las grullas marcadas con transmisores PTT de las afiliaciones EC–M y WC–A respectivamente, realizaron migraciones de primavera que incluyeron sitios de escala al este de Dakota del Sur por un promedio de 11 y 10 días respectivamente. Grullas de las subpoblaciones NC–N, WA–S, y WC–A pararon un promedio de 25, 17, y 12 días en el centro y el oeste de Saskatchewan/este de Alberta. Se estima que a partir de Nebraska, las hembras de estas afiliaciones aumentaron sus reservas de grasa corporal en 450, 451, y 452 g respectivamente, enfatizando la importancia de estas áreas de escala en la preparación de las 3 subpoblaciones para la reproducción. Al dejar Nebraska, las grullas de la MCP durmieron principalmente en lagunas de cuenca. Muchas de estas lagunas se encuentran en propiedades privadas y carecen de protección adecuada, enfatizando la necesidad de implementar leyes y políticas efectivas que aseguren su protección a largo plazo. La continuidad del éxito de la actual gestión de la MCP, con el objetivo de mantener aproximadamente su tamaño actual y proveer diversas oportunidades recreativas a través de una amplia área del centro y oeste de Norte América, está ligada a la habilidad de las grullas de la MCP de almacenar grandes reservas de grasa corporal en anticipación a la reproducción. Para que el CPRV se mantenga como un sitio importante para la acumulación de grasa corporal en las grullas canadienses, se proponen el mantenimiento activo del canal (e.g., remoción de árboles) y el establecimiento de un flujo mínimo en el río. Estas acciones ayudarían a asegurar que suficientes dormideros nocturnos permanezcan disponibles para que las grullas se puedan dispersar adecuadamente y puedan acceder a su dieta, limitando de esta manera el riesgo de alta mortalidad asociado con tormentas y enfermedades. Nous avons conduit une étude sur une période de 10 ans (1998–2007) sur la population mi‐continentale (MCP) des grues du Canada (Grus canadensis) pour identifier les couloirs de migration printaniers, les escales principales et la chronologie de migration selon l'affiliation reproductive des grues observées (Ouest de l'Alaska‐Sibérie [WA–S], Nord Canadien‐Nunavut [NC–N], Centre Ouest Canadien [WC–A], et le Centre Est Canadien‐Minnesota [EC–M]). Nous avons évalué les facteurs qui influencent la chronologie des périodes de repos, les habitudes alimentaires, le surplus de gras et l'utilisation de l'habitat des grues du Canada dans la vallée de la rivière Platte au Nebraska (CPRV). Nous avons comparé nos résultats avec l'étude sur l'écologie de la rivière Platte conduite entre 1978–1980. Les couloirs migratoires printaniers utilisés dans l'affiliation reproductive (sous‐populations désignées ci‐haut pour aider à la gestion) ont été déterminés après avoir surveillé et suivi 169 grues identifiées par une borne de transmission plate‐forme (PTT). Nous avons également identifié et surveillé 456 grues dans la région de la rivière Platte (CPRV) avec des transmetteurs ayant une très haute fréquence de transmission (VHF) dans le but d'évaluer la durée et leur tendance de séjour, l'utilisation de l'habitat et leurs mouvements. Entre 42% et 58% de l'aire de repos des grues du Canada (Grus canadensis tabida) dans la région de la rivière Platte était plus grande que celle des grues du Canada (Grus canadensis) qui elles sont restées respectivement en moyenne entre 20 et 25 jours (2000–2007). Les grues appartenant aux régions WA–S, NC–N, WC–A, et EC–M ont voyagé lors de leur migration printanière en moyenne 72, 77, 52, et 53 jours et ils ont passé respectivement en moyenne 28, 23, 24, et 18 jours dans la région de la rivière Platte (CPRV). La majorité de la sous‐population WA–S s'est installée dans la région de la rivière Platte (CPRV) à case d'un habitat inadéquat en amont pour supporter plus d'oiseaux, même si les grues WA–S représentaient >90% des oiseaux qui ont choisi la rivière Platte comme aire de repos. Le temps passé dans la région de la rivière Platte (CPRV) est négativement corrélée avec leurs dates d'arrivées, 92% des grues sont restées >7 jours. Un programme annuel de désherbage mécanique des plantules et des plantes ligneuses matures qui a commencé au début des années 1980 a aider la distribution des gîtes de grue à rester relativement stable au cours des 2 dernières décennies. La plupart des grues sont retournées dans leurs perchoirs nocturnes utilisées les années précédentes. Les résidus de maïs ont dominé le régime des grues dans la vallée de la Rivière Platte (CPRV), tout comme dans les années 1970, malgré une baisse considérable de la récolte des résidus des plants de maïs. Seulement 14% (10 sur 74) des grues identifiées par le système PTT sont restées dans un aire de repos ≥5 jours avant d'arriver dans la vallée de la rivière Platte (CPRV), ce qui limite la contribution des sites au sud de la CPRV pour aider à l'accumulation des gras nécessaires pour la migration et la reproduction. Les masses corporelles des grues (après avoir été ajusté pour la taille corporelle [un indice de masse grasses]) à leur arrivée dans la CPRV variaient considérablement selon les années étudiées (1998–2006), ce qui indique l'importance de maintenir des habitats productifs dans les aires de repos pour inciter la migration et la reproduction des grues du Canada. Les taux moyens d'accumulation de graisses par les femelles adultes lors de leur séjour dans la CPRV est demeuré stable de 1978–1979 à 1998–1999, mais a diminué chez les males. Les distances voyagées par les grues pour se rendre dans des aires d'alimentation dans la région de la CPRV ont augmenté ainsi que le pourcentage des terres arables plantées de soja et la densité des grues sur les racines nocturnes. Ces résultats suggèrent que les habitats de peu ou sans valeurs pour les grues se sont multipliées dans la région, plus de temps de vol est nécessaire, ce qui augmente les coûts de maintenance tout en réduisant les réserves de gras. On estime que 40% de l'utilisation diurne est survenue au nord de l'Interstate 80 (I‐80) où ≤5% des terres vouées à la conservation des grues sont situées. Lors de la migration printanière des grues EC–M et WC–A, 74% et 40% de celles‐ci se sont reposées dans le sud‐est du Dakota du Sud pour une moyenne respective de 11 et 10 jours. Les grues des sous‐populations NC–N, WA–S, et WC–A se sont reposées en moyenne 25, 17, et 12 jours dans le centre et l'ouest de la Saskatchewan et l'est de l'Alberta. Les femelles de ces affiliations ont augmenté leurs réserves de gras respectives d'environ 450, 451, et 452g lors de leur repos au Nebraska, ce qui souligne l'importance clé de ces aires de repos dans le cycle préparatoire pour la reproduction de ces trois sous‐populations. Après s'avoir envolé du Nebraska, les grues de la mi‐continentale se sont principalement perchés dans des bassins et des zones humides. La plupart de ces terres humides et ces bassins se retrouvent sur des propriétés privées et elles manquent de protection adéquate pour protéger les grues. Ceci met l'emphase sur la nécessité de lois et politiques efficaces pour assurer la protection à long terme des grues du Canada. Le succès continue de l'objectif actuel de gestion pour maintenir la population mi‐continentale des grues du Canada à sa taille actuelle ainsi que d'offrir diverses possibilités de loisirs sur une large zone mi‐continentale et de l'Ouest de l'Amérique du Nord repose sur la capacité des grues de faire de grandes réserves de gras avant la saison d'élevage. Pour que la région de la vallée de la rivière Platte (CPRV) demeure un site important pour faire des réserves de gras, le maintien des terres doit être actif, ce qui inclut la continuation du défrichement des zones de végétation ligneuses ainsi que l'établissement minimal des débits d'eau. Ces mesures contribueraient à assurer que suffisamment d'aire de repos nocturnes demeurent à la disponibilité des grues du Canada lors de leur migration et assureraient de satisfaire leurs besoins alimentaires ce qui aidera les grues à se disperser et en conséquence limitera le risque de mortalité élevé dû aux tempêtes et aux maladies. Нами проведены 10‐летние исследования (1998–2007 гг.) по изучению весенних миграционных коридоров, основных мест транзитных остановок, хронологии миграций средне‐континентальной популяции (СКП) канадского журавля (Grus canadensis) из различных мест размножения вида (Западная Аляска ‐ Сибирь [ЗА–С], Северная Канада–Нунавут [СК–Н], Западно‐центральная Канада–Аляска [ЗК–A], и Восточно‐центральная Канада–Миннесота [ВК–M]; Крапу и др. 2011). В Центральной долине реки Плат (ЦДРП) в штате Небраска нами оценены факторы, влияющие на хронологию перемещений канадских журавлей, их пищевые предпочтения, накопление жира и использование местообитаний. Результаты наших исследований были сравнены с результатами работ по Исследованию Экологии Реки Плат, проводившимися в 1978–1980 гг. (Служба рыбы и дичи США, 1981). Коридоры весенних миграций, используемые журавлями с различных мест размножения (выявленные для целей управления субпопуляциями) были определены путем спутникового мониторинга 169 журавлей с датчиками РТТ (Platform Transmitter Terminals). Также в ЦДРП нами были помечены 456 птиц высокочастотными спутниковыми датчиками VHF (Very High Frequency) для оценки продолжительности и характера их пребывания, использования местообитаний, и передвижений. Отмечено, что 42 и 58% журавлей на транзитной остановке в ЦДРП были представлены двумя подвидами, соответственно, большим (G. c. tabida), и малым канадским журавлями (G. c. canadensis), которые держались на территории в среднем 20– 25 дней (2000–2007 гг.). Журавли из ЗА–С, СК–Н, ЗК–А и ВК–M потратили в среднем 72, 77, 52 и 53 дней, соответственно, на весеннюю миграцию, из которых 28, 23, 24 и 18 дней провели в ЦДРП. Вероятно, что большая часть особей субпопуляции ЗА–С держались в ЦДРП из‐за нехватки подходящих местообитаний, необходимых для поддержания большого количества птиц, выше по течению, хотя журавли субпопуляции ЗА–С составляли >90% птиц, отмеченных в Северной Долине Реки Плат. Продолжительность остановки журавлей в ЦДРП имеет отрицательную корреляцию с датами прибытия; 92% журавлей пребывали на местах остановки >7 дней. Программа ежегодного механического удаления зрелых насаждений деревьев и саженцев, которая началась в 1980‐х, позволила распределению мест кормления журавлей в течение последних двух десятилетий оставаться относительно стабильным. Большинство журавлей возвращались в места кормления, используемые ими в предыдущие годы. Остатки кукурузы преобладали в рационе канадских журавлей в ЦДРП, как и в 1970‐х гг., несмотря на заметное снижение урожая кукурузы. Только 14% (10 из 74) РТТ‐меченых мигрирующих журавлей держались на остановках в течение ≥5 дней до прибытия в ЦДРП, что ограничивало вклад южных от ЦДРП территорий для накопления жира, необходимого для миграции и размножения птиц. Масса тела журавлей (с поправкой на размер тела [индекс жира]) по прибытии в CPRV различалась по годам (1998–2006), что указывает на важность сохранения продуктивных местообитаний на зимовках, необходимых для миграционного и репродуктивного состояния журавлей. Средние темпы роста жира у взрослых самок в ЦДРП оставались одинаковыми с 1978–1979 по 1998–1999, но снизились среди самцов. Дистанции полетов журавлей на места кормежек в ЦДРП увеличились в связи с увеличением доли соевых угодий на данной территории, также наблюдалось повышение плотности журавлей на ночных местах кормления. Эти результаты позволяют предположить, что некачественные и не имеющие ценности обширные угодья требуют больше времени на перелет, и эти энергетические затраты могут уменьшить накопление жира. По нашим оценкам, 40% суточного использования территорий происходило к северу от внутреннего штата 80 (I‐80), где ≤5% земель определены под охрану журавлей. 74 и 40% PTT‐меченых ВК–М и ЗК–А журавлей во время весенних миграций останавливались в восточной части Южной Дакоты в среднем на 11 и 10 дней соответственно. Журавли субпопуляций СК–Н, ЗА–С и ЗК–А останавливались в среднем на 25, 17 и 12 дней в центральном и западном Саскачеване/восточной Альберте. Самки из данных группировок увеличили свои жировые запасы на 450, 451, и 452 г соответственно, что подчеркивает ключевую роль кормовых угодий Небраски в подготовке трëх субпопуляций для размножения. После отлета из Небраски, СКП журавлей кормились, прежде всего, в водно‐болотных угодьях. Многие из этих водно‐болотных угодий находятся в частной собственности и не имеют адекватной охраны, что подчеркивает необходимость эффективных законов и политики для обеспечения их долговременной защиты. Продолжающееся успешное управление по поддержанию СКП канадского журавля примерно соответствует целям управления в полном размере, и предоставляет разнообразные рекреационные возможности на большой территории средне‐континентальной и западной части Северной Америки, которое основано на возможности СКП канадского журавля накапливать большие запасы жиры перед периодом размножения. Для того, чтобы ЦДРП продолжала оставаться важным местом накопления жира журавлями, нужна дальнейшая активная работа по поддержке доступности водного канала, которая включает очистку древесной растительности, а также установление минимального количества водных потоков. Эти меры помогут обеспечить достаточное количество ночных мест кормления, доступных журавлям, чтобы птицы могли быть адекватно распределены по территории для удовлетворения своих кормовых потребностей, с целью сокращения риска высокой смертности от неблагоприятных погодных условий и болезней. © 2014 The Wildlife Society.

A spring hunt was instituted in North America to reduce abundance of snow geese (Chen caerulescens) by increasing mortality of adults directly, yet disturbance from hunting activities can indirectly influence body condition and ultimately, reproductive success. We estimated effects of hunting disturbance by comparing body composition of snow geese and non-target species, greater white-fronted geese (Anser albifrons) and northern pintails (Anas acuta) collected in portions of south-central Nebraska that were open (eastern Rainwater Basin, ERB) and closed (western Rainwater Basin, WRB; and central Platte River Valley, CPRV) to snow goose hunting during springs 1998 and 1999. Lipid content of 170 snow geese was 25% (57?g) less in areas open to hunting compared to areas closed during hunting season but similar in all areas after hunting was concluded in the ERB. Protein content of snow geese was 3% (14?g) less in the region open to hunting. Greater white-fronted geese had 24% (76?g; n?=?129) less lipids in the hunted portion of the study area during hunting season, and this difference persisted after conclusion of hunting season. We found little difference in lipid or protein content of northern pintails in relation to spring hunting. Indirect effects of spring hunting may be considered a collateral benefit regarding efforts to reduce overabundant snow goose populations. Disrupted nutrient storage observed in greater white-fronted geese represents an unintended consequence of spring hunting that has potential to adversely affect reproduction for this and other species of waterbirds staging in the region. © 2012 The Wildlife Society.

Waterfowl and other migratory birds commonly store nutrients at traditional staging areas during spring for later use during migration and reproduction. We investigated nutrient-storage dynamics in the midcontinent population of greater white-fronted geese (Anser albifrons; hereafter white-fronted geese) at spring staging sites in the Rainwater Basin of Nebraska during February–April and in southern Saskatchewan during April–May, 1998 and 1999. In Nebraska, lipid content of white-fronted geese did not increase, and protein content changed little over time for most age and sex categories. In Saskatchewan, lipids increased 11.4?g/day (SE?=?1.7) and protein content increased 1.6?g/day (SE?=?0.6) in the sample of adult geese collected over a 3-week period. A study conducted during 1979–1980 in the Rainwater Basin reported that white-fronted geese gained 8.8–17.7?g of lipids per day during spring, differing greatly from our results 2 decades later. In addition, lipid levels were less in the 1990s compared to spring 1980 for adult geese nearing departure from staging sites in Saskatchewan. This shift in where geese acquired nutrient stores from Nebraska to more northern staging sites coincided with a decrease in availability of waste corn in Nebraska, their primary food source while staging at that stopover site, and an increase in cultivation of high-energy pulse crops in Saskatchewan. White-fronted geese exhibited flexibility in nutrient dynamics during spring migration, likely in response to landscape-level variation in food availability caused by changes in agricultural trends and practices. Maintaining a wide distribution of wetlands in the Great Plains may allow spring-staging waterfowl to disperse across the region and facilitate access to high-energy foods over a larger cropland base. © 2011 The Wildlife Society.

The Mid‐continent Population (MCP) of sandhill cranes (Grus canadensis) is widely hunted in North America and is separated into the Gulf Coast Subpopulation and Western Subpopulation for management purposes. Effective harvest management of the MCP requires detailed knowledge of breeding distribution of subspecies and subpopulations, chronology of their use of fall staging areas and wintering grounds, and exposure to and harvest from hunting. To address these information needs, we tagged 153 sandhill cranes with Platform Transmitting Terminals (PTTs) during 22 February–12 April 1998–2003 in the Central and North Platte River valleys of south‐central Nebraska. We monitored PTT‐tagged sandhill cranes, hereafter tagged cranes, from their arrival to departure from breeding grounds, during their fall migration, and throughout winter using the Argos satellite tracking system. The tracking effort yielded 74,041 useable locations over 49,350 tag days; median duration of tracking of individual cranes was 352 days and 73 cranes were tracked >12 months. Genetic sequencing of mitochondrial DNA (mtDNA) from blood samples taken from each of our random sample of tagged cranes indicated 64% were G. c. canadensisand 34% were Grus canadensis tabida. Tagged cranes during the breeding season settled in northern temperate, subarctic, and arctic North America (U.S. [23%, n= 35], Canada [57%, n= 87]) and arctic regions of northeast Asia (Russia [20%, n= 31]). Distribution of tagged cranes by breeding affiliation was as follows: Western Alaska–Siberia (WA–S, 42 ± 4% [SE]), northern Canada–Nunavut (NC–N, 21 ± 4%), west‐central Canada–Alaska (WC–A, 23 ± 4%) and East‐central Canada–Minnesota (EC–M, 14 ± 3%). All tagged cranes returned to the same breeding affiliation used during the previous year with a median distance of 1.60 km (range: 0.08–7.7 km, n= 53) separating sites used in year 1 and year 2. Fall staging occurred primarily in central and western Saskatchewan (69%), North Dakota (16%), southwestern Manitoba (10%), and northwestern Minnesota (3%). Space‐use sharing indices showed that except for NC–N and WC–A birds, probability of finding a crane from one breeding affiliation within the home range of another breeding affiliation was low during fall staging. Tagged cranes from WC–A and EC–M breeding affiliations, on average, spent 25 and 20 days, respectively, longer on fall staging areas in the northern plains than did WA–S and NC–N birds. Cranes in the NC–N, WA–S, and WC–A affiliations spent 99%, 74%, and 64%, respectively, of winter in western Texas in Hunting Zone A; EC–M cranes spent 83% of winter along the Texas Gulf Coast in Hunting Zone C. Tagged cranes that settled within the breeding range of the Gulf Coast Subpopulation spent 28% and 42% of fall staging and winter within the range of the Western Subpopulation, indicating sufficient exchange of birds to potentially limit effectiveness of MCP harvest management. Harvests of EC–M and WC–A cranes during 1998–2003 were disproportionately high to their estimated numbers in the MCP, suggesting more conservative harvest strategies may be required for these subpopulations in the future, and for sandhill cranes to occupy major parts of their historical breeding range in the Prairie Pothole Region. Exceptionally high philopatry of MCP cranes of all 4 subpopulations to breeding sites coupled with strong linkages between crane breeding distribution, and fall staging areas and wintering grounds, provide managers guidance for targeting MCP crane harvest to meet management goals. Sufficient temporal or spatial separation exists among the 4 subpopulations on fall staging areas and wintering grounds to allow harvest to be targeted at the subpopulation level in all states and provinces (and most hunting zones within states and provinces) when conditions warrant. Knowledge gained from our study provides decision‐makers in the United States, Canada, Mexico, and Russia with improved guidance for developing sound harvest regulations, focusing conservation efforts, and generating collaborative efforts among these nations on sandhill crane research and management to meet mutually important goals. © 2011 The Wildlife Society. La Población Centro‐continental (MCP) de grulla canadiense (Grus canadensis) es cazada ampliamente en Norte América y, para propósitos de manejo, está dividida en las Subpoblaciones de la Costa del Golfo y Oeste. Una gestión efectiva de la especie requiere un conocimiento detallado sobre la distribución de las áreas reproductivas de subespecies y subpoblaciones, la cronología del uso de las áreas de escala durante el otoño y de las áreas de invernada, así como la exposición y presión a la cacería. Para poder obtener estos conocimientos necesarios, marcamos 153 grullas canadienses con transmisores PTT (Platform Transmitter Terminal) entre el 22 de febrero y el 12 de abril de 1998 a 2003 en los valles del Central Platte River y North Platte River, localizados en la zona centro sur de Nebraska. Monitoreamos las grullas marcadas con transmisores PTT (en lo sucesivo grullas marcadas), desde su llegada hasta su partida a las zonas de reproducción, durante su migración de otoño y durante todo el período de invierno, utilizando el sistema de seguimiento por satélite ARGOS. Dicho seguimiento dio como resultado 74,041 localizaciones útiles de un total de 49,350 días; la duración mediana de seguimiento de individuos fue de 352 días y 73 grullas fueron rastreadas >12 meses. Las secuencias genéticas de ADN Mitocondrial en sangre, tomadas a partir de muestras aleatorias de grullas marcadas, indicaron que el 64% eran G. c. canadensisy el 34% eran Grus canadensis tabida. Durante la estación reproductiva, las grullas marcadas se establecieron en las regiones templadas, subárticas, y árticas de Norte América (Estados Unidos [23%, n= 35], Canadá [57%, n= 87]) así como en las regiones árticas del nordeste de Asia (Rusia [20%, n= 31]). Las grullas marcadas, pertenecientes a diferentes afiliaciones reproductivas, se distribuyeron de la siguiente forma: Oeste de Alaska–Siberia (WA–S, 42 ± 4% [SE]), norte de Canadá–Nunavut (NC–N, 21 ± 4%), centro oeste de Canadá–Alaska (WC–A, 23 ± 4%) y centro este de Canadá–Minesota (EC–M, 14 ± 3%). Todas las grullas marcadas regresaron a la misma afiliación reproductiva del año anterior con una distancia mediana de 1.60 km (rango: 0.08–0.77 km, n= 53) de separación entre los sitios utilizados en el año 1 y en el año 2. Las áreas de escala otoñal se concentraron principalmente en el centro y oeste de Saskatchewan (69%), Dakota del Norte (16%), sudoeste de Manitota (10%) y noroeste de Minesota (3%). Los índices de compartimiento de espacio indicaron que a excepción de las aves NC–N y WC–A, la probabilidad de encontrar una grulla perteneciente a una afiliación reproductiva dentro del territorio de otra afiliación, era baja durante la escala otoñal. Las aves WC–A y EC–M pasaron respectivamente como promedio 25 y 20 días más en las áreas de escala otoñal de las grandes planicies, que las aves WA–S y NC–N. Las grullas pertenecientes a las afiliaciones NC–N, WA–S y WC–A pasaron el 99, 74 y 64% del invierno respectivamente, en el oeste de Texas en la Zona de Caza A; las grullas EC–M pasaron el 83% del invierno a lo largo de la Costa del Golfo de Texas en la Zona de Caza C. Las grullas marcadas que se asentaron en las áreas de reproducción de la Subpoblación de la Costa del Golfo, pasaron el 28% de la escala otoñal y el 42% del invierno dentro del territorio de la Subpoblación Oeste, indicando un intercambio de individuos lo suficiente grande como para potencialmente limitar el manejo efectivo de la MCP. La caza de aves EC–M y WC–A entre los años 1998 a 2003 fue desproporcionalmente alta en relación a los números estimados en la MCP, sugiriendo que se podrían requerir estrategias de manejo más conservadoras para estas subpoblaciones en un futuro, y para que la grulla canadiense pueda reocupar gran parte de su área reproductiva histórica en la región del Prairie Pothole. El hecho de que las 4 subpoblaciones de grullas pertenecientes a la MCP exhibieron una excepcional filopatría a los sitios de reproducción y de que existieron fuertes vínculos entre las distribuciones reproductivas de las grullas, las áreas de escala otoñal y las áreas de invernada, ofrece una orientación a los manejadores de la caza de grullas de la MCP para que puedan cumplir con las metas de gestión establecidas. Existe suficiente separación temporal y/o espacial entre las 4 subpoblaciones en las áreas de escala otoñal y en las áreas de invernada como para permitir la caza dirigida al nivel subpoblacional en todos los estados y provincias (y en la mayoría de las zonas de caza dentro de los estados y provincias) siempre y cuando las condiciones lo ameriten. El conocimiento obtenido a partir de este estudio proporciona a los responsables de decisiones en los Estados Unidos, Canadá, México y Rusia, una mejor dirección para desarrollar cuotas de caza razonables, enfocar los esfuerzos en materia de conservación y generar colaboraciones entre estas naciones en materia de investigación y gestión de la grulla canadiense, para poder cumplir metas importantes y a la vez comunes. La grue du Canada (Grus canadensis) est largement chassée en Amérique du Nord et elle se sépare entre la sous‐population côtière du Golfe et la sous‐population de l'Ouest afin de tel que défini. Pour administrer la population des grues efficacement, il est nécessaire d'avoir une connaissance détaillée de la répartition des colonies, des sous‐espèces et des sous‐populations. Il faut aussi une table chronologique des divers points de ravitaillements visités par ces grues et leur exposition aux dangers de la chasse au cours de leur migration. Pour répondre à ce besoin, nous avons étiqueté cent cinquante‐trois (153) grues du Canada avec des bornes de transmission plate‐forme (VTP), entre le 22 février et le 12 avril des années 1998 et 2003, au centre et au nord de la vallée de la Rivière Platte dans le sud‐central du Nebraska. Grâce au système de repérage satellite ARGOS, nous avons contrôlé les bornes de transmission (VTP) des grues du Canada étiquetées, de leur arrivé jusqu'à leur départ des zones de reproduction, pendant la migration printanière et tout au long de la période hivernale. L'effort de repérage a localisé 74,041 lieux utilisés sur une période de 49,350 jours. Le suivi des grues individuelles était d'une durée médiane de 352 jours, dont 73 grues ont étés repérées sur une période de plus de douze mois. Le séquençage génétique de l'ADNmt à partir de certains échantillons de sang prélevé sur des grues étiquetées au hasard a démontré que 64% étaient des G. c. canadensiset que 34% étaient des Grus canadensis tabida. Les grues étiquetées durant la saison de reproduction se sont installées majoritairement dans les régions tempérées, subarctiques et arctiques de l'Amérique du Nord (États‐Unis [23%, n= 35], Canada [57%, n= 87]) ainsi que dans les régions de l'Arctique de l'Asie du Nord (Russie [20%, n= 31]). La répartition des grues étiquetées lors de la reproduction a démontré les affiliations suivantes: Ouest de l'Alaska–Sibérie (OA–S, 42 ± 4% [SE]), Nord du Canada–Nunavut (NC–N, 21 ± 4%), Centre‐Ouest du Canada–Alaska (COC–A, 23 ± 4%) et Centre‐Est du Canada–Minnesota (CEC–M, 14 ± 3%). Toutes les grues étiquetées sont retournées dans les mêmes groupes de reproduction que les années précédentes, quoiqu'une distance médiane de 1.60 km (gamme: 0.08–7.7 km, n= 53) séparait les sites entre les deux années étudiées. Les relais automnaux des grues étudiées sont principalement situés dans le centre et l'ouest de la Saskatchewan (69%), au Dakota du Nord (16%), dans le sud‐ouest du Manitoba (10%) et dans le nord‐ouest du Minnesota (3%). Les indices de partage d'espace ont démontré qu'à l'exception des grues du NC–N et du COC–A, les probabilités de trouver une grue dans le domaine vital d'une autre affiliation de reproduction que la sienne est très faible lors de la saison d'accouplement. Les grues étiquetées provenant des zones de reproduction du COC–A et du CEC–M passent, respectivement, en moyenne 25 et 20 jours de plus en automne dans les plaines du nord que les oiseaux des régions OA–S et du NC–N. Les grues se situant dans les affiliations du NC–C, de l'OA–A et du COC–A ont respectivement passé 99, 74, et 64% de leur hiver dans l'ouest du Texas, zone de chasse A. Les grues du CEC–M ont passé 83% de leur hiver le long de la région de la Côte du Golfe du Texas, dans la zone de chasse C. Les grues étiquetées qui se sont installées dans la zone d'accouplement de la sous‐population côtière du Golfe, ont passé entre 28 et 42% de la saison d'accouplement et de la saison hivernale dans la région de la sous‐population de l'Ouest. Cela indique qu'un échange suffisant entre les deux populations de grues peut potentiellement limiter l'effet de la gestion de la reproduction. L'étude des grues du CEC–M et du COC–A en 1998 et 2003 a démontré une disproportion vis‐à‐vis du nombre estimé de la PGCC, suggérant que de nouvelles stratégies conservatrices sont nécessaire pour que les sous‐populations de grue du Canada réoccupent la majorité de leur territoire historique de la région des cuvettes des prairies. Les quatre sous‐populations de grues de la PGCC ressentent une philopatrie exceptionnelle entre leurs sites de reproduction respectifs, leurs sites d'élevage, leurs lieux de rassemblement automnaux et leurs relais hivernaux. Cette philopatrie offre aux chasseurs une cible incroyable pour gérer et atteindre leurs objectifs quand vient la saison de la chasse. Parmi les quatre sous‐populations, une séparation temporelle et spatiale suffisante existe entre les aires de repos automnales et hivernales. Quand les conditions le permettent, cette séparation permet aux grues des sous‐populations d'être la cible des chasseurs durant la saison de chasse dans tous les états et toutes les provinces (et dans la plupart des zones de chasses). Les connaissances acquises lors de cette étude permettent aux États‐Unis, au Canada, au Mexique et à la Russie de pouvoir améliorer leurs lois en ce qui à trait à la saison de la reproduction. Elle aide aussi ces pays à diriger leurs efforts sur la conservation des grues et de leur territoire. Finalement, elle génère une nouvelle collaboration entre ces quatre nations en matière de recherche et de gestion sur les grues du Canada, pour répondre à ces objectifs mutuels.

ABSTRACT The central Platte River valley (CPRV) in Nebraska, USA, is a key spring-staging area for approximately 80% of the midcontinent population of sandhill cranes (Grus canadensis; hereafter cranes). Evidence that staging cranes acquired less lipid reserves during the 1990s compared to the late 1970s and increases in use of the CPRV by snow geese (Chen caerulescens) prompted us to investigate availability of waste corn and quantify spatial and temporal patterns of crane and waterfowl use of the region. We developed a predictive model to assess impacts of changes in availability of corn and snow goose abundance under past, present, and potential future conditions. Over a hypothetical 60-day staging period, predicted energy demand of cranes and waterfowl increased 87% between the late 1970s and 1998–2007, primarily because peak abundances of snow geese increased by 650,000 and cranes by 110,000. Compared to spring 1979, corn available when cranes arrived was 20% less in 1998 and 68% less in 1999; consequently, the area of cornfields required to meet crane needs increased from 14,464 ha in 1979 to 32,751 ha in 1998 and 90,559 ha in 1999. Using a pooled estimate of 88 kg/ha from springs 1998–1999 and 2005–2007, the area of cornfields needed to supply food requirements of cranes and waterfowl increased to 65,587 ha and was greatest in the eastern region of the CPRV, where an estimated 54% of cranes, 47% of Canada geese (Branta canadensis), 45% of greater white-fronted geese (Anser albifrons), and 46% of snow geese occurred during ground surveys. We estimated that a future reduction of 25% in available corn or cornfields would increase daily foraging flight distances of cranes by 27–38%. Crane use and ability of cranes to store lipid reserves in the CPRV could be reduced substantially if flight distance required to locate adequate corn exceeded a physiological maximum distance cranes could fly in search of food. Options to increase carrying capacity for cranes include increasing accessibility of cornfields by restoring degraded river channels to disperse roosting cranes and increasing wetland availability in the Rainwater Basin to attract snow geese using the CPRV.

ABSTRACT We evaluated food habits of 4 species of spring-migrant calidrid sandpipers in the Prairie Pothole Region (PPR) of North Dakota. Sandpipers foraged in several wetland classes and fed primarily on aquatic dipterans, mostly larvae, and the midge family Chironomidae was the primary food eaten. Larger sandpiper species foraged in deeper water and took larger larvae than did smaller sandpipers. The diverse wetland habitats that migrant shorebirds use in the PPR suggest a landscape-level approach be applied to wetland conservation efforts. We recommend that managers use livestock grazing and other tools, where applicable, to keep shallow, freshwater wetlands from becoming choked with emergent vegetation limiting chironomid production and preventing shorebird use.

AbstractWe used radiotelemetry to study mallard (Anas platyrhynchos) brood movements, wetland use, and duckling survival during a major drought (1988–1992) and during the first 2 years of the subsequent wet period (1993–1994) at 4 51-km2sites in prairie pothole landscapes in eastern North Dakota, USA. About two-thirds of 69 radiomarked mallard broods initiated moves from the nest to water before noon, and all left the nest during daylight. On average, broods used fewer wetlands, but moved greater distances during the dry period than the wet period. Broods of all ages were more likely to make inter-wetland moves during the wet period and probabilities of inter-wetland moves decreased as duckling age increased, especially during the dry period. Brood use of seasonal wetlands nearly doubled from 22% to 43% and use of semi-permanent wetlands declined from 73% to 50% from the dry to the wet period. Eighty-one of 150 radiomarked ducklings died during 1,604 exposure days. We evaluated survival models containing variables related to water conditions, weather, duckling age, and hatch date. Model-averaged risk ratios indicated that, on any given date, radiomarked ducklings were 1.5 (95% CI = 0.8–2.8) times more likely to die when the percentage of seasonal basins containing water (WETSEAS) was =18% than when WETSEAS was >40%. An interaction between duckling age and occurrence of rain on the current or 2 previous days indicated that rain effects were pronounced when ducklings were 0–7 days old but negligible when they were 8–30 days old. The TMIN (mean daily minimum temperature on the current and 2 previous days) effects generally were consistent between duckling age classes, and the risk of duckling death increased 9.3% for each 1°C decrease in TMIN across both age classes. Overall, the 30-day survival rate of ducklings equipped with radiotransmitters was about 0.23 lower than the survival rate of those without radiotransmitters. Unmarked ducklings were 7.6 (95% CI = 2.7–21.3) times more likely to die on any given day when WETSEAS was =18% than when WETSEAS was >40%. Higher duckling survival and increased use of seasonal wetlands during the wet period suggest that mallard production will benefit from programs that conserve and restore seasonal wetland habitat. Given adverse effects of low temperatures on duckling survival, managers may want to include this stochastic variable in models used to predict annual production of mallards in the Prairie Pothole Region.

Abstract: In the Prairie Pothole Region (PPR) of North Dakota, USA, American mink (Mustela vison) are a major predator of ducklings. Mink populations plummet during severe droughts, but some mink survive where permanent fresh water is available. In 1992–1993, we evaluated whether development of a permanent water body, the 125-km McClusky Canal (MC), had affected survival of gadwall (Anas strepera) and mallard (A. platyrhynchos) broods and ducklings in surrounding wetland complexes. Twelve of 25 radiomarked gadwall and mallard hens experienced total brood loss, and 148 of 199 radiomarked ducklings from 58 broods died by day 30. Gadwall broods (n= 18 radiomarked hens) survived to 30 days at a lower rate (0.52) than predicted for similar areas in the region with limited permanent fresh water (0.85; P= 0.009). Observed (n= 162 radiomarked ducklings from 48 broods) survival rates also were lower than predicted for gadwall ducklings 0–7 days old (0.42 vs. 0.60; P< 0.001) and 8–30 days old (0.41 vs. 0.80; P< 0.001). We attempted to include mallards in models constructed to predict brood and duckling survival rates in the Koenig Study Area (KSA), but data were too sparse. Rates of survival to 30 days for gadwall and mallard ducklings declined from an estimated 0.83 and 0.68 in 1976–1981 (Lokemoen et al. 1990), when the MC was first filling with water, to 0.36 and 0.31 (adjusted for radiotransmitter effects) in 1992–1993 after the MC had become a permanent freshwater body. Estimated gadwall recruitment rate (females fledged per hen) during 1992–1993 was 0.5, <50% of the estimated recruitment rate in 1976–1981. Of 130 radiomarked ducklings (both species) for which we determined cause of death, 114 mortalities were attributed to predation; at least 65% of 62 deaths in which the predator type could be discerned were caused by mink. Environmental planners and waterfowl managers should be aware of potential risks to waterfowl production from development of permanent freshwater bodies in prairie pothole landscapes and may wish to refine duck productivity models to consider negative effects of permanent water on duckling survival.