The Platte River Program A USGS Priority Ecosystems Program

The Platte River Program—Work Unit Study Proposal

U.S. Geological Survey
Biological Resources Division
Northern Prairie Wildlife Research Center
Work Unit Study Proposal

Study Plan 169.01: Spring staging ecology of greater white-fronted geese, lesser snow geese, and northern pintails in the central Platte River Valley and Rainwater Basin of Nebraska

Principal Investigator: Robert R. Cox, Jr.

Background and Justification:
The central Platte River Valley (CPRV) and adjacent Rainwater Basin Area (RBA) of Nebraska are major stopover areas for migratory waterfowl and shorebirds during late winter and spring. Major waterfowl species using these areas include greater white-fronted geese (Anser albifrons; hereafter white-fronted geese), lesser snow geese (Chen caerulescens; hereafter snow geese), Canada geese (Branta canadensis), mallards (Anas platyrhynchos), and northern pintails (Anas acuta; hereafter pintails). Despite the loss of over 90% of original wetlands (Tiner 1984), abundant corn (Zea mays) agriculture is an important factor contributing to the large numbers of waterfowl that concentrate on a reduced wetland base in this region.

Snow geese and white-fronted geese rely heavily on nutrient reserves (lipid and protein) accumulated during spring migration for egg laying and/or incubation (Ankney and MacInnes 1978, Wypkema and Ankney 1979, Alisauskas 1988, Budeau et al. 1991, Krapu et al. 1995). Female pintails obtain most lipids used for reproduction south of breeding areas (Krapu 1974). Nesting pintails rely on endogenous lipids to greater degree than other ducks (Esler and Grand 1994), and lipid dynamics prior to arriving at breeding areas may influence initiation of nesting, clutch size, and other aspects of recruitment in pintails (Raveling and Heitmeyer 1989).

Muscle tissue is the primary storage medium for protein in birds. Because muscle tissue contains about 75% water, protein is more costly for birds to transport than lipids (Blem 1976). Although female pintails anabolize much protein for nesting after arriving on breeding areas (Krapu 1974), protein accumulated during spring migration may be important for subsequent reproduction. Thus, wet meadows and other riparian areas of CPRV and shallow basins of the RBA may be important sources of invertebrates and, subsequently, for protein deposition by pintails, particularly considering the close proximity of these areas to the Prairie Pothole Region, a primary breeding area for pintails in North America. Mallards wintering in the CPRV foraged extensively in riparian areas for invertebrates (Jorde et al. 1983).

The Midcontinent population of snow geese has increased dramatically in recent years, to the point of causing serious habitat destruction on Arctic breeding areas (Ankney 1996). The problem of too many snow geese is very evident during spring migration in the RBA of Nebraska, where numbers of snow geese have increased from only incidental flocks during the early 1980's to several million during the late 1990's (P. J. Gabig, Nebraska Game and Parks Comm., pers. comm.).

Although Krapu et al. (1995) concluded that waste corn densities in the CPRV and RBA during 1979-80 were adequate to support white-fronted goose populations at that time, potential improvements in corn harvesting efficiency and increased snow goose numbers may be limiting corn availability to waterfowl in recent years. Waterfowl managers in the region are concerned that increased numbers of snow geese staging in the CPRV and RBA may lead to increased risk of disease (primarily avian cholera) as waterfowl densities increase on wetlands, and increased competition with sandhill cranes (Grus canadensis), white-fronted geese, and other waterfowl for food resources through depletion and/or active exclusion. Recent information collected by G. L. Krapu suggests that sandhill cranes are markedly leaner during spring in recent years than they were in the late 1970's (Krapu et al. 1985). A clear understanding of diets and nutrient-reserve dynamics of principal waterfowl species is needed to effectively manage spring-staging habitat in this region. Further, information on how land-use practices and changes in snow goose populations influence the number of use days for various waterfowl species that this region can support is essential to waterfowl management and planning in the region. Efforts by managers to rehabilitate natural habitats in the CPRV and RBA within the agricultural landscape matrix that is so critical to providing food resources to sandhill cranes and many waterfowl species will benefit from an assessment of waterfowl diets and health of the ecosystem.


  1. To measure daily rates and magnitude of fat and protein deposition by immature and adult white-fronted geese, adult snow geese, and female pintails during the spring-staging interval in the CPRV and RBA and compare nutrient-reserve dynamics of white-fronted geese to patterns observed in 1979-80.
  2. To examine diet composition of white-fronted geese, snow geese, and pintails during late winter and early spring and compare diets of white-fronted geese to those during 1979-80.
  3. To quantitatively assess diurnal time-activity budgets of white-fronted geese and snow geese, including agonistic interactions and interspecific dominance relationships between these species.
  4. To develop a predictive model to estimate effects of changes in densities of waterfowl (primarily snow geese) and land-use patterns (abundance of corn agriculture and proportion of post-harvest treatments applied to corn fields as they affect waste corn availability) on the number of use days by white-fronted geese and other waterfowl and birds that forage in agricultural fields that the CPRV and RBA can support.

Study Area and Field Season Chronology:
During 2 late winters and early springs (1998 and 1999), we will conduct fieldwork (bird collections, time-activity budgets, and corn availability sampling) within the CPRV and RBA (Fig. 1). Exact timing of fieldwork will depend on weather and migration phenology, but we expect the field season to begin in early to mid-February and end in early April. Waterfowl arriving early in the region may concentrate in the CPRV, and later move to the RBA when those wetlands thaw and become available. We will try to allocate collections between the CPRV and RBA in proportion to relative numbers of white-fronted geese, snow geese, and pintails in each area on a weekly basis. The Nebraska Game and Parks Commission (NGPC) intends to conduct weekly aerial surveys of snow geese throughout the region. We will rely on close communication with survey personnel, land managers in each area, and our own observations to monitor gross temporal changes in relative distributions of bird species between these areas.

Diet and nutrient-reserves.--We will collect all sex and age classes of white-fronted geese in order to compare current nutrient deposition rates to those in 1979-80 (Krapu et al. 1995). Comparative data are not available for snow geese or pintails in the region; hence, we will collect only adult snow geese and female pintails because these groups are the most important to recruitment, among those that can be differentiated under field conditions. We will distinguish age class of geese and sex class of pintails in the field prior to collection by differences in plumage. Sample size goals each year are 100 white-fronted geese (25 of each sex and age class), 80 adult snow geese (40 males, 40 females), and 80 female pintails (40 adult, 40 immature). We will temporally distribute collections of each species as evenly as possible between arrival and departure of these species from the CPRV and RBA (approximately 12.5 white-fronted geese, 10 snow geese, and 10 pintails collected each week for 8 weeks).

Field-feeding is expected to be common for white-fronted geese and snow geese, but less so for pintails. We will collect white-fronted geese and snow geese primarily by shooting birds at riparian or wetland roost sites in the evening as they return from fields. This strategy should increase the proportion of collected geese containing food for diet analysis compared to shooting birds leaving roosts en route to fields (either in the morning or early afternoon), and should eliminate site bias in food habits associated with collecting geese in fields (geese collected from corn fields likely will contain primarily corn, those from wheat [Triticum aestivum] fields likely will contain primarily wheat, etc. [Alisauskas 1988]). We may be able to collect pintails in this manner, but expect to expend additional effort collecting pintails in riparian areas, including wet meadows, and on wetlands in the RBA. We will follow standard procedures when collecting pintails (Swanson and Bartonek 1970). When possible, we will watch pintails feed for 10 minutes prior to collecting. We will determine sex and age class of geese using cloacal examination and tail-feather characteristics (Hochbaum 1942), and age class of female pintails using wing-plumage characteristics (Duncan 1985). We will weigh (+ 5 g) each specimen following collection, and measure (1) total tarsus length (Dzubin and Cooch 1992), (2) middle toe length, (3) culmen, (4) head length, and (5) flattened wing chord. We will inject the esophagus and proventriculus with 2-3 ml of ethanol immediately following collection, and place a plastic tie at the base of the head to prevent spillage. Later on the day of collection, we will remove the esophagus and proventriculus and preserve them and their contents in 80% ethanol in individually labeled jars. We will restrict food habits analysis to esophagi, unless <50% of the birds contain food, in which case we will analyze foods from the esophagi and proventriculi separately, test for differences between these organs, and combine if not different. Foods will be sorted, dried to constant mass at 55 degrees C, and weighed to the nearest 0.0001 g. We will express foods as frequency of occurrence and aggregate percent dry mass (Swanson et al. 1974). Entire carcasses (minus esophagi, proventriculi, and their contents) will be frozen and later shipped to the University of Western Ontario where they will be plucked, analyzed for lipids (duplicate petroleum ether extraction using a Soxhlet apparatus), mineral (duplicate ash determination using a muffle furnace), and ash-free lean dry mass (a reliable index of protein) following standardized procedures (Horwitz 1975). Ingesta from the gizzard and lower gastrointestinal tract will be removed and weighed prior to carcass composition analysis.

Time-activity budgets.--Information on how bird species apportion time to various activities will be important for estimating daily energy expenditures (DEE) and subsequent assessment of waterfowl energetic needs relative to available food resources. Frequency, duration, and outcome of interspecific agonistic behaviors may be an important component of DEE for white-fronted geese, particularly if snow goose populations remain at current levels or continue to increase. We will estimate time-activity budgets for white-fronted geese and snow geese, but not for pintails. Each of 2 technicians will will collect time-activity budget data on 3 days per week (2 mornings and 1 afternoon). Morning sessions will extend from 30 minutes before sunrise until 1300 CST, and afternoon sessions will extend from 1300 CST until 30 minutes after sunset. We will begin morning sessions at major roosts (as determined from weekly surveys by NGPC), and we will roll a die to determine whether to follow a flock prior (1, 2, or 3) or following (4, 5, or 6) half of the birds initially present on the wetland have departed. We will roll the die a second time to randomly select which flock (first, second, third, fourth, fifth, or sixth) to follow to diurnal feeding sites. If most individuals depart in a single flock, we will follow the largest group. We will begin afternoon sessions at major concentrations as determined by weekly surveys by NGPC. We will record distance and duration of flights.

At feeding sites, we will record location (township, range, and section), field type (wheat, corn, etc.) and post-harvest treatment (e.g, idle, grazed [see below]), numbers of waterfowl and sandhill cranes present by species (exact counts for species groups of <50 individuals, nearest 10 for species groups of 50-500, nearest 100 for species groups of 501-2000, and nearest 1000 for larger groups), cloud cover (nearest 10%), and wind velocity (Beaufort scale) prior to initiating observations. We will note whether birds of each species are present in monospecific flocks or intermixed with flocks of other species. We will record time-budget data following Krapu et al. (1995) in order to facilitate comparison with previous years. We will select randomly an individual goose (focal individual) and record his activities at 10-sec intervals for as long as possible up to 30 min (Weins et al. 1970). Activities recorded will be resting, feeding, alert, walking/swimming, flying, preening, courtship, and agonistic. For agonistic activities, we also will record species with which the focal individual was interacting, and if the interaction was interspecific, which species was dominant. We will note displays and postures (Boyd 1953, Raveling 1970) to help determine outcomes of agonistic interactions. If the focal individual is involved in an interspecific interaction when the observation period is scheduled to end, we will discontinue recording behaviors at 10-sec intervals, but continue to monitor the individual until an outcome (dominant, subordinate, or neither) is determined.

Following completion of monitoring a focal individual, we again will record numbers of waterfowl and cranes present, cloud cover, and wind velocity, and randomly select another focal individual. This process will continue at the same site unless over half of the flock moves, in which case we will follow the largest group either to an alternative foraging site or to a roosting wetland. We will record flight duration and distances on these occasions. We will discontinue time-activity observations at 30 minutes past sunset because white-fronted geese and snow geese are inactive at night during spring migration (Alisauskas and Ankney 1992, Krapu et al. 1995). If geese at roost sites during early morning have not initiated departures by 15 minutes after sunrise, we will begin collecting time-activity data on roost sites as above.

Predictive model for use days.--Information on food availability will be needed to develop the predictive model for waterfowl use days that the CPRV and RBA can support. Estimates of amounts of land allocated to various types of agriculture by county are available from annual reports (U.S. Department of Agriculture 1909-97). However, frequency of post-harvest treatments (idle, grazed, disked/chisel plowed, shredded, baled, or moldboard plowed) applied to cornfields in the region are not known. To estimate the proportion of cornfields receiving various post-harvest treatments, we will select randomly 50 sections of land within the CPRV, eastern RBA, and western RBA. We will visit each section once yearly immediately after snowmelt (early to mid-February). From the roadside, we will select the first cornfield 4.0-64.7 ha (10-160 acres) in size encountered starting at the northeastern corner of the selection section and driving clockwise (initially south) around the section. We will delineate the approximate size of each cornfield and record presence/absence of each post-harvest treatment for each field. We will rely on data collected concurrently on foods available to foraging sandhill cranes to estimate density and biomass of waste corn within fields available to foraging waterfowl (G. L. Krapu, pers. comm.). These data are being collected on cornfields during fall (immediately following harvest), late winter/early spring (immediately following snowmelt), and late spring (after most cranes and waterfowl have moved through the area). Decreasing foraging efficiency prevents waterfowl from using all grain in croplands (reviewed by Reinecke et al. 1989), and mallards feeding by sight in dry fields typically reduce corn biomass to 15 kg/ha (Baldassarre and Bolen 1984). Thus, estimates of biomass of corn available to foraging waterfowl can be generated using the following equation:

Total Corn Biomass (kg) = (Biomass [kg/ha] in post-harvest typei - 15) * Land in typei (ha)

Waste corn biomass for post-harvest treatments producing less than 15 kg/ha, on average, will be considered zero. We will use published estimates of true metabolizable energy for corn to convert biomass estimates to energy content (e.g., Petrie et al. 1997).

We will index the ability of the CPRV and RBA to fulfill the needs of spring-staging waterfowl using several sources of data: (1) comparing current daily lipid deposition rates of white-fronted geese to those during 1979-80, (2) comparing current rates of decrease in corn availability between late winter/early spring and late-spring samples to those in 1979-80, (3) estimating biomass of corn needed by current populations of white-fronted geese, snow geese, Canada geese, sandhill cranes, pintails, and mallards and comparing estimates of need with those of availability. We will estimate corn importance for white-fronted geese, snow geese, and pintails by multiplying their estimated energy requirements by the proportion of dietary energy derived from corn. The number of waterfowl of each species that can be supported by the amount of corn available in the CPRV and RBA then can be estimated. We will use published estimates of DEE (either species specific or allometric equations based on body mass) for Canada geese, sandhill cranes, mallards, and pintails.

As an alternative means of assessing how well the needs of present populations are met by agricultural resources within the CPRV and RBA, a general model of this type has been developed by M. J. Petrie et al. (M. J. Petrie, Ducks Unlimited, pers. comm.). This model has been applied to a wide variety of situations (e.g., redheads [Aythya americana] foraging on shoal grass (Halodule spp.) on Laguna Madre, Texas, and carrying capacity of the rice-prairie region of Texas in relation to increasing numbers of snow geese). We will apply the general model to the CPRV and RBA, and expect the results to be useful for model validation and for refining parameters estimated by this study.

Data Analysis:
For each species, we will test for variation in diets and time-activity budgets in relation to year, sex and/or age class, and Julian date using compositional data analysis and multivariate analysis of variance (Aitchison 1986, Aebischer et al. 1993). We will test for variation in body mass and nutrient reserves of each species in relation to year, sex and/or age class, Julian date, and body size (as indexed by the first principal component from the correlation matrix of the structural size measurements) using analysis of covariance. We also will examine variation in diets and nutrient reserves of white-fronted geese in relation to time period (1979-80 or 1998-99). We will use logistic regression or proportional odds models (Agresti 1990) to test for differences in dominance following interspecific interactions between goose species.

Hazard Assessment:
Technicians must pass state-certified hunter safety courses, and will be given further instruction on safe use of firearms. No further unusual hazards are associated with this study.

Animal Welfare:
All collections will be done by personnel experienced with firearms (technicians and Principal Investigator). Study specimens will be killed swiftly using shotguns. Crippled birds will be dispatched immediately by thoracic constriction .

Results from this study will be submitted as peer-reviewed manuscripts to scientific journals, and also will be presented at scientific and flyway council meetings.

Literature Cited:

Aebischer, N. J., P. A. Robertson, and R. E. Kenward. 1993. Compositional data analysis of habitat use from animal radio-tracking data. Ecology 74:1313-1325.

Aitchison, J. 1986. The statistical analysis of compositional data. Chapman and Hall, London, U.K. 416pp.

Agresti, A. 1990. Categorical data analysis. John Wiley & Sons, New York. 558pp.

Alisauskas, R. T. 1988. Nutrient reserves of lesser snow geese during winter and spring migration. Ph.D. Thesis, Univ. Western Ontario, London. 261pp.

Alisauskas, R. T., and C. D. Ankney. 1992. Spring habitat use and diets of midcontinent adult lesser snow geese. J. Wildl. Manage. 56:43-54.

Ankney, C. D. 1996. An embarrassment of riches: too many geese. J. Wildl. Manage. 60:217-223.

Ankney, C. D., and C. D. MacInnes. 1978. Nutrient reserves and reproductive performance of female lesser snow geese. Auk 95:459-471.

Baldassarre, G. A., and E. G. Bolen. 1984. Field-feeding ecology of waterfowl wintering on the Southern High Plains of Texas. J. Wildl. Manage. 48:63-71.

Blem, C. R. 1976. Patterns of lipid storage and utilization in birds. Amer. Zool. 16:671-684.

Boyd, H. 1953. On encounters between wild white-fronted geese in winter flocks. Behaviour 5:85-129.

Budeau, D. A., J. T. Ratti, and C. R. Ely. 1991. Energy dynamics, foraging ecology, and behavior or prenesting greater white-fronted geese. J. Wildl. Manage. 55:556-563.

Duncan, D. C. 1985. Differentiating yearling from adult northern pintails by wing-feather characteristics. J. Wildl. Manage. 49:576-579.

Dzubin, A., and E.G. Cooch. 1992. Measurements of geese: general field methods. California Waterfowl Assoc., Sacramento, California. 20pp.

Esler, D. and J. B. Grand. 1994. The role of nutrient reserves for clutch formation by northern pintails in Alaska. Condor 96:422-432.

Hochbaum, H. A. 1942. Sex and age determination of waterfowl by cloacal examination. Trans. North Am. Wildl. Nat. Resour. Conf. 7:299-307.

Horwitz, W. 1975. Official methods of analysis. Assoc. Off. Anal. Chem., Washington, D.C. 1094pp.

Jorde, D. G., G. L. Krapu, and R. D. Crawford. 1983. Feeding ecology of mallards wintering in Nebraska. J. Wildl. Manage. 47:1044-1053.

Krapu, G. L. 1974. Feeding ecology of pintail hens during reproduction. Auk 91:278-290.

Krapu, G. L., G. C. Iverson, K. J. Reinecke, and C. M. Boise. 1985. Fat deposition and usage by arctic-nesting sandhill cranes during spring. Auk 102:362-368.

Krapu, G. L., K. J. Reinecke, D. G. Jorde, and S. G. Simpson. 1995. Spring-staging ecology of midcontinent greater white-fronted geese. J. Wildl. Manage. 59:736-746.

Petrie, M. J., R. D. Drobney, and D. A. Graber. 1997. Evaluation of true metabolizable energy for waterfowl. J. Wildl. Manage. 61:420-425.

Raveling, D. G. 1970. Dominance relationships and agonistic behavior of Canada geese in winter. Behaviour 37:291-319.

Raveling, D. G., and M. E. Heitmeyer. 1989. Relationships of population size and recruitment of pintails to habitat conditions and harvest. J. Wildl. Manage. 53:1088-1103.

Reinecke, K. J., R. M. Kaminski, D. J. Moorhead, J. D. Hodges, and J. R. Nassar. 1989. Mississippi Alluvial Valley. Pages 203-247 in L. M. Smith, R. L. Pederson, and R. M. Kaminski, eds., Habitat management for migrating and wintering waterfowl in North America. Texas Tech Univ. Press, Lubbock.

Swanson, G. A., and J. C. Bartonek. 1970. Bias associated with food analysis in gizzards of blue-winged teal. J. Wildl. Manage. 34:739-746.

Swanson, G. A., G. L. Krapu, J. C. Bartonek, J. R. Serie, and D. H. Johnson. 1974. Advantages of mathematically weighting waterfowl food habits data. J. Wildl. Manage. 38:302-307.

Tiner, R. W., Jr. 1984. Wetlands of the United States: current status and recent trends. U.S. Gov. Print. Off., Washington, D.C. 50pp.

U.S. Department of Agriculture. 1909-97. Nebraska agricultural statistics: annual summaries. Nebraska Agric. Stat. Serv., Lincoln.

Weins, J. A., S. G. Martin, W. R. Holthaus, and F. A. Iwen. 1970. Metronome timing in behavioral ecology studies. Ecology 51:350-352.

Wypkema, R. C. P., and C. D. Ankney. 1979. Nutrient reserve dynamics of lesser snow geese staging at James Bay, Ontario. Can. J. Zool. 57:213-219.

Work Schedule:
Fieldwork (first field season) Feb-Apr 1998
Labwork (food habits and carcass composition analysis) May-Aug 1998
Preliminary data analysis Sep-Oct 1998
Progress report December 1998
Fieldwork (second field season) Feb-Apr 1999
Labwork (food habits and carcass composition analysis) May-Aug 1999

Final data analysis Sep-Oct 1999
Manuscript preparation and submission Dec 1999-June 2000

Annual Budget (U.S. Funds):

2 GS-7 for 6 pp each @ $1078/pp $12,936
2 4WD GSA vehicles for 2 mo. @ $177/mo. each $708
mileage: 5,000 miles ea. per mo. @ $0.22/mi. $4,400
Shotguns: available at Northern Prairie $0
Shotgun shells: 30 bxs. at $12.00/bx. $360

Carcass composition:
freezer storage in Nebraska $500
shipping of carcasses $500
100 white-fronted geese @ $95.88/bird $9588
80 snow geese @ $95.88/bird $7670
80 pintails @ $95.88/bird $7670

Travel and per diem for PI:
mileage (1 week and 1 weekend) $600
housing: USFWS bunkhouse $0
per diem: 10 d @ $30/d $300
Travel to coordination meetings $2,000

Misc. expenses: $268


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