Population Of Sandhill Cranes Research Articles

Short-term effects of camera trap installation on incubation constancy in cranes

Research regarding how birds respond to the installation of cameras at nest sites is limited. We installed cameras at nests of Sandhill Cranes Antigone canadensis ( Linnaeus, 1758 ) and federally endangered Whooping Cranes Grus americana Linnaeus, 1758 in Juneau County, WI, as part of an ongoing study monitoring the reproductive success of Whooping Cranes in WI. The eastern population of Sandhill Cranes has grown, while Whooping Crane population growth has been slow, prompting the need to monitor the reproductive success of cranes on the refuge. We recorded the flight initiation distance during camera installation, the return time after camera installation, as well as measured the distance at which cameras were placed from each nest. We included temperature at camera deployment, age of nest, mode of access, ordinal date, and year in statistical regression models. We found an apparent difference in the observed flight initiation distances between the two species. Sandhill Cranes allowed researchers to approach their nests closer than Whooping Cranes prior to flushing. The post-disturbance return time was influenced by how far away the cameras were placed from the nest and the ambient temperature during camera deploy. Our study may help inform decisions regarding species response to methods and distance when deploying cameras, especially for endangered or disturbance-sensitive species.

An Updated Minimum Estimate of the Global Sandhill Crane Population

An Updated Minimum Estimate of the Global Sandhill Crane Population

Breeding expansion of sandhill cranes in Quebec

AbstractSandhill cranes (Antigone canadensis) were broadly extirpated from much of their historical range in North America at the beginning of the twentieth century. Various conservation‐related legislation, such as the United States Migratory Bird Treaty Act, have assisted with population recovery. The eastern population of sandhill cranes has been growing rapidly since the 1980s and is thought to have expanded its geographic range to Quebec, Canada. Understanding the colonization and habitat use by the species in previously unoccupied breeding areas is necessary to develop and apply management measures. Using a dynamic occupancy modeling approach, we investigated the recent colonization and extirpation patterns of sandhill cranes in Quebec from 2004–2019. We combined data from 3 data sets (helicopter surveys, breeding bird atlas surveys, and eBird) to increase the spatial coverage and the number of species occurrence records while accounting for imperfect detection probability. Detection probability was highest for the helicopter survey (0.70), whereas the 2 other data sets had relatively low detection levels (0.10–0.26). Based on a simulation study, we found that excluding the eBird data from the analysis produced more biased estimates than excluding the atlas and helicopter survey data sets. Throughout the study, sandhill cranes seemed to have completed their colonization of western Quebec and only recently started to nest in eastern areas. Initial occupancy increased with wetland cover and colonization probability increased weakly with the cover of agricultural areas, suggesting that in our study area sandhill cranes rely essentially on natural wetlands during the breeding season.

Population responses to harvest depend on harvest intensity, demographics, and mate replacement in sandhill cranes

Recent examinations of hunting’s impact on populations of long-lived species illustrate the rarity of strong compensatory responses. The extent to which sandhill crane populations exhibit compensatory, partially compensatory, or additive responses to harvest mortality is poorly known. To examine how sandhill crane harvests might impact resident, breeding crane populations, we simulated harvests of a well-studied population of individually marked birds at varying harvest intensities and degrees of selectivity within the social structure of territorial and non-territorial cranes. Simulations occurred in a demographically-explicit stochastic population model developed from a previous long-term (2000–2014) study of a sandhill crane population at carrying capacity in southcentral Wisconsin, USA. Non-selective harvest models that did not account for reproductive lags after territorial birds replaced lost mates produced additive responses and resulted in declining populations when ≥ 7% of the population was harvested annually. When models of non-selective harvest incorporated reproductive lags, this threshold was reduced to ≥ 5%. Harvesting at or above 5% harvest intensities continuously decreased population size over a 100-year period. In all models of selective harvests, when only non-territorial birds were harvested, all populations returned to equilibrium. Population responses to harvest are sensitive to the number of territorial birds harvested, and this sensitivity increases when accounting for lags in reproduction stemming from mortality-induced mate replacement. If possible, limiting harvest of territorial birds from any one specific population would help maintain stability of populations when implementing a hunt. This study provides evidence for harvest impacts at a localized scale, and it represents an important first step toward better understanding the potential impacts of hunting on population responses at a regional scale, especially where resident, territorial birds might be harvested.

Sandhill Crane abundance in Nebraska during spring migration: making sense of multiple data points

The USFWS conducts an annual one-day aerial survey of the North and Central Platte River Valleys, generally on the fourth Tuesday in March, to estimate the abundance of the midcontinent Sandhill Crane population. However, these abundance indices demonstrate unrealistic inter-annual variation as a result of deviations in migration chronology and other factors. Additional research efforts have been undertaken within the region to estimate Sandhill Crane abundance over time and space but these projects generally seek to answer unique questions, employ differing survey methods, and cover overlapping yet distinct survey areas. Despite the wealth of information there remains significant uncertainty regarding the actual abundance of Sandhill Cranes in Nebraska during the peak of migration. We conducted a model-based metadata analysis relying on the distinctive strengths of three databases to assess USFWS data, identify annual abundance estimates that may not be robust, and developed parameter-based and factorbased corrections to USFWS indices from 2000 to 2019. Our analyses suggest that at the peak of spring migration there is likely between 1.1 and 1.4 million Sandhill Cranes in the North and Central Platte River Valleys of Nebraska. Our best performing models indicated the most likely peak estimate was 1.27 million Sandhill Cranes with approximately 220,000 in the North Platte River Valley and 1,050,000 in the Central Platte River Valley in both 2018 and 2019. Our assessment suggests that 25% of USFWS aerial estimates are robust, with the rest representing underestimates as both exogenous and endogenous factors such as migration chronology and survey methodology serve to bias indices downward. Given this downward bias, the three-year running average used by the USFWS actually provides a robust estimate for only 5–15% of the years analyzed. By contrast, we found that a five-year rolling maximum provides a robust estimate for 70–75% of the years analyzed.

Using morphological measurements to predict subspecies of Midcontinent sandhill cranes

ABSTRACTThe Midcontinent population of sandhill cranes (Antigone canadensis) has historically been classified into 3 putative subspecies, but genetic analyses have identified only 2 genetically distinct subspecies. Previous studies have successfully used morphometrics in combination with an individual's sex to differentiate subspecies of sandhill cranes that had been inferred based on breeding area, but no study has used a sample of genetically determined subspecies to discriminate and develop predictive models. Using measurements from 843 adult sandhill cranes captured throughout their range and annual cycle (in 4 States and 1 Canadian province during 1998–2007), we used linear discriminant analysis to classify genetically identified A. c. canadensis (lesser) and A. c. tabida (greater) sandhill crane subspecies, and developed a field‐ready tool to predict subspecies using common morphometric measurements without determination of an individual's sex. Our top‐ranked model was 89.5% accurate overall, and used flattened wing chord, total culmen, and tarsometatarsus lengths to correctly identify 93.1% of A. c. canadensis and 82.8% of A. c. tabida subspecies. Additionally, we identified measurement thresholds based on posterior probabilities of correct classification to aid in subspecies determination when the linear discriminant procedure provided equivocal results. We also investigated whether sex determination could increase accuracy of our top‐ranked model, and found that accuracy increased <1% when including this information. We suggest collection of the morphometric measurements used in our top‐ranked model to determine subspecies of adult Midcontinent sandhill cranes. Our method does not require determining sex of the individual to correctly classify subspecies, allows for accurate and rapid subspecies determination, and can largely avoid additional costs and time associated with genetic analyses to determine subspecies. © 2019 The Wildlife Society.

Adaptive management of animal populations with significant unknowns and uncertainties: a case study.

Conservation and management decision making in natural resources is challenging due to numerous uncertainties and unknowns, especially relating to understanding system dynamics. Adaptive resource management (ARM) is a formal process to making logical and transparent recurrent decisions when there are uncertainties about system dynamics. Despite wide recognition and calls for implementing adaptive natural resource management, applications remain limited. More common is a reactive approach to decision making, which ignores future system dynamics. This contrasts with ARM, which anticipates future dynamics of ecological process and management actions using a model-based framework. Practitioners may be reluctant to adopt ARM because of the dearth of comparative evaluations between ARM and more common approaches to making decisions. We compared the probability of meeting management objectives when managing a population under both types of decision frameworks, specifically in relation to typical uncertainties and unknowns. We use a population of Sandhill Cranes as our case study. We evaluate each decision process under varying levels of monitoring and ecological uncertainty, where the true underlying population dynamics followed a stochastic age-structured population model with environmentally driven vital rate density dependence. We found that the ARM framework outperformed the currently employed reactive decision framework to manage Sandhill Cranes in meeting the population objective across an array of scenarios. This was even the case when the candidate set of population models contained only naïve representations of the true population process. Under the reactive decision framework, we found little improvement in meeting the population objective even if monitoring uncertainty was eliminated. In contrast, if the population was monitored without error within the ARM framework, the population objective was always maintained, regardless of the population models considered. Contrary to expectation, we found that age-specific optimal harvest decisions are not always necessary to meet a population objective when population dynamics are age structured. Population managers can decrease risks and gain transparency and flexibility in management by adopting an ARM framework. If population monitoring data has high sampling variation and/or limited empirical knowledge is available for constructing mechanistic population models, ARM model sets should consider a range of mechanistic, descriptive, and predictive model types.

Summer Habitat Selection of the Lower Colorado River Valley Population of Greater Sandhill Cranes

Abstract 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.

Haemosporida prevalence and diversity are similar in endangered wild whooping cranes (Grus americana) and sympatric sandhill cranes (Grus canadensis).

The population growth of endangered whooping cranes (Grus americana) is not consistent with species recovery goals, and the impact of parasite infection on whooping crane populations is largely unknown. Disease ecology and epidemiology research of endangered species is often hindered by limited ability to conduct invasive sampling on the target taxa. Accordingly, we hypothesized that sandhill cranes (Grus canadensis) would be a useful surrogate species to investigate the health impacts of Haemosporida infection in whooping cranes. Our goal was to compare the prevalence and diversity of Haemosporida infection between whooping cranes and sandhill cranes. We detected an overall infection prevalence of 83·6% (n = 61) in whooping cranes and 59·6% (n = 47) and 63·6 (n = 22) in two sympatric sandhill crane populations captured in Texas. Prevalence was significantly lower in allopatric sandhill cranes captured in New Mexico (12·1%, n = 33). Haemoproteus antigonis was the most abundant haemoparasite in cranes, present in 57·4% of whooping cranes and 39·2% of sandhill cranes; Plasmodium and Leucocytozoon were present at significantly lower levels. The high prevalence of Haemosporida in whooping cranes and sympatric sandhill cranes, with shared parasite lineages between the two species, supports sandhill cranes as a surrogate species for understanding health threats to endangered whooping cranes.

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

Abstract 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.

Annual Survival Rate Estimate of Satellite Transmitter–Marked Eastern Population Greater Sandhill Cranes

Abstract Several surveys have documented the increasing population size and geographic distribution of Eastern Population greater sandhill cranes Grus canadensis tabida since the 1960s. Sport hunting of this population of sandhill cranes started in 2012 following the provisions of the Eastern Population Sandhill Crane Management Plan. However, there are currently no published estimates of Eastern Population sandhill crane survival rate that can be used to inform harvest management. As part of two studies of Eastern Population sandhill crane migration, we deployed solar-powered global positioning system platform transmitting terminals on Eastern Population sandhill cranes (n = 42) at key concentration areas from 2009 to 2012. We estimated an annual survival rate for Eastern Population sandhill cranes from data resulting from monitoring these cranes by using the known-fates model in the MARK program. Estimated annual survival rate for adult Eastern Population sandhill cranes was 0.950 (95% confidence interval = 0.885–0.979) during December 2009–August 2014. All fatalities (n = 5) occurred after spring migration in late spring and early summer. We were unable to determine cause of death for crane fatalities in our study. Our survival rate estimate will be useful when combined with other population parameters such as the population index derived from the U.S. Fish and Wildlife Service fall survey, harvest, and recruitment rates to assess the effects of harvest on population size and trend and evaluate the effectiveness of management strategies.

Ecosickness in Contemporary US Fiction: Environment and Affect by Heather Houser

<i>Ecosickness in Contemporary US Fiction: Environment and Affect</i> by Heather Houser

Timing of spring surveys for midcontinent sandhill cranes

ABSTRACTThe U.S. Fish and Wildlife Service has used spring aerial surveys to estimate numbers of migrating sandhill cranes (Grus canadensis) staging in the Platte River Valley of Nebraska, USA. Resulting estimates index the abundance of the midcontinent sandhill crane population and inform harvest management decisions. However, annual changes in the index have exceeded biologically plausible changes in population size (&gt;50% of surveys between 1982 and 2013 indicate &gt;±20% change), raising questions about nuisance variation due to factors such as migration chronology. We used locations of cranes marked with very‐high‐frequency transmitters to estimate migration chronology (i.e., proportions of cranes present within the Platte River Valley). We also used roadside surveys to determine the percentage of cranes staging at the Platte River Valley but outside of the survey area when surveys occur. During March 2001–2007, an average of 86% (71–94%; SD = 7%) of marked cranes were present along the Platte River during scheduled survey dates, and 0–11% of cranes that were present along the Platte River were not within the survey boundaries. Timing of the annual survey generally corresponded with presence of the greatest proportion of marked cranes and with least inter‐annual variation; consequently, accuracy of estimates could not have been improved by surveying on different dates. Conducting the survey earlier would miss birds not yet arriving at the staging site; whereas, a later date would occur at a time when a larger portion of birds may have already departed the staging site and when a greater proportion of birds occurred outside of the surveyed area. Index values used to monitor midcontinent sandhill crane abundance vary annually, in part, due to annual variation in migration chronology and to spatial distribution of cranes in the Platte River Valley; therefore, managers should interpret survey results cautiously, with awareness of a continuing need to identify and understand components of variation. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.

Spring migration ecology of the mid‐continent sandhill crane population with an emphasis on use of the Central Platte River Valley, Nebraska

ABSTRACTWe 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 &gt;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 &gt;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.

Utility of vocal formant spacing for monitoring sandhill crane subspecies

AbstractThree migratory subspecies of sandhill crane (Grus canadensis) occur in North America: greater (G. c. tabida), Canadian (G. c. rowani), and lesser (G. c. canadensis). These subspecies vary clinally in size from the large tabida to the small canadensis. All 3 subspecies co‐occur during the nonbreeding season, but field identification is challenging and census efforts typically do not even attempt to distinguish them. We developed a novel method to determine the subspecies composition of nonbreeding sandhill crane populations using formant spacing in vocalizations. Each note in a crane vocalization is comprised of several formants, or energy peaks in the frequency spectrum. Formant spacing is inversely proportional to the length of the sound‐emitting tube, or trachea. Analysis of formant‐spacing distributions for tabida and canadensis revealed that tabida has reduced formant spacing, as predicted based on its larger body size and correspondingly larger trachea. Comparisons of these subspecies‐specific formant‐spacing distributions to formant‐spacing distributions from calls recorded at 2 crane wintering areas in New Mexico, USA, showed that the wintering crane populations of the Middle Rio Grande Valley and the Lower Rio Grande Valley contain strikingly different proportions of the globally rare tabida (75.5% and 5.6%, respectively). These findings are concordant with crane subspecies composition estimates derived from hunter check stations in New Mexico. Formant‐spacing provides an indirect, noninvasive method of estimating body‐size distributions that has several practical advantages. We expect it to be most useful when body‐size classes have limited overlap, as is the case with New Mexico sandhill crane populations. © 2012 The Wildlife Society.

Geographic distribution of the mid‐continent population of sandhill cranes and related management applications

AbstractThe 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 &gt;12 months. Genetic sequencing of mitochondrial DNA (mtDNA) from blood samples taken from each of our random sample of tagged cranes indicated 64% wereG. c. canadensisand 34% wereGrus 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.

Changes in Agriculture and Abundance of Snow Geese Affect Carrying Capacity of Sandhill Cranes in Nebraska

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.

Extra-Pair Fertilizations in Sandhill Cranes Revealed Using Microsatellite DNA Markers

AbstractAbstractThe presence of extra-pair fertilizations (EPF) in a dense breeding population of Sandhill Cranes (Grus canadensis) was examined using six microsatellite DNA markers. In this long-lived species that maintains long-term pair bonds, 4.4%–11% of 45 chicks were not genetically related to one social parent, and extra-pair chicks were present in 5.6%–22% of 18 family groups. Two confirmed extra-pair chicks were from different broods of the same pair that was socially bonded for a minimum of 12 years. The social male was rejected as the genetic father of both of these chicks. Three other potential cases of EPF (two cases in which the social male was rejected as the genetic parent, one in which the social female was rejected) could also have resulted from mate replacement prior to sampling. The range of EPF in this population of Sandhill Cranes is similar to that of other species with similar mating systems. In the confirmed cases of EPF, the female was able to increase her individual reproductive success without losing her territory.

Platte River Birding and the Spring Migration: Humans, Value, and Unique Ecological Resources

Each spring Sandhill Cranes migrate north through the Platte River region to nesting grounds. Wildlife watchers were surveyed to understand the extent to which they valued the ecological resources that provided birding opportunities. A mail questionnaire containing scenarios (with a cost attached to each) focused on management programs to preserve the present status of the river, proposed changes in species diversity, and on Sandhill Crane population levels. Birders were willing to bear the cost of resource conservation, particularly those expenses related to efforts to protect Sandhill Cranes and their habitats. Also, crane population declines were viewed as a diminishment in value, and thus lower numbers of cranes would lead to decreased recreational activity. Birders were less supportive of programs to conserve or enhance wildlife diversity. Birders were likely attracted by the wildlife spectacle rather than unusual or unique species. Overall, they valued species diversity less than species abundance.

EXTRA-PAIR FERTILIZATIONS IN SANDHILL CRANES REVEALED USING MICROSATELLITE DNA MARKERS

Abstract ABSTRACT The presence of extra-pair fertilizations (EPF) in a dense breeding population of Sandhill Cranes (Grus canadensis) was examined using six microsatellite DNA markers. In this long-lived species that maintains long-term pair bonds, 4.4%–11% of 45 chicks were not genetically related to one social parent, and extra-pair chicks were present in 5.6%–22% of 18 family groups. Two confirmed extra-pair chicks were from different broods of the same pair that was socially bonded for a minimum of 12 years. The social male was rejected as the genetic father of both of these chicks. Three other potential cases of EPF (two cases in which the social male was rejected as the genetic parent, one in which the social female was rejected) could also have resulted from mate replacement prior to sampling. The range of EPF in this population of Sandhill Cranes is similar to that of other species with similar mating systems. In the confirmed cases of EPF, the female was able to increase her individual reproducti...