Duck Broods Research Articles

Wetland occupancy by duck broods in cropland‐dominated landscapes of the United States Prairie Pothole Region

AbstractThe Prairie Pothole Region (PPR) is globally important for breeding waterfowl but has been altered via wetland drainage and grassland conversion to accommodate agricultural land use. Thus, understanding the ecology of waterfowl in these highly modified landscapes is essential for their conservation. Brood occurrence is the cumulative outcome of key life‐history events including pair formation and territory establishment, nest success, and early brood survival. We applied new technological advances in brood surveying methods to understand brood use of wetlands and how land use and wetland‐specific factors influenced brood use of 413 wetlands in crop‐dominated landscapes in the PPR of Iowa, Minnesota, North Dakota, and South Dakota, USA, during summers of 2018–2020. Dynamic occupancy models combining information from 2 visits throughout the year revealed no difference among the 4 states or between private and public lands, resulting in a region‐wide annual wetland occupancy estimate of 0.41 (95% credible interval [CrI] = 0.26, 0.58). We assessed aquatic invertebrate forage availability, wetland and upland vegetation communities, and various water chemistry metrics in a subset (n = 225) of these wetlands to evaluate how landscape and wetland‐specific factors influenced occupancy. The amount of grassland surrounding wetlands was the only variable to influence occupancy at a landscape scale, while wetland size, invertebrates, fish, and vegetation communities influenced occupancy at finer scales. Closer scrutiny of wetland area revealed occupancy was greater in small wetlands after controlling for total wetland area. Our results indicate the greatest constraint on brood occupancy across crop‐dominated landscapes of the PPR in the United States was the occurrence of semipermanent wetlands suitable for brood rearing. Other factors, such as wetland vegetation or surrounding land use, had minor intervening influences on duck brood use and ducks were distributed invariant of wetland ownership or broad spatial processes occurring among states. These results demonstrated wetland conservation and restoration strategies are likely to yield gains in annual duck broods across this vast, altered, and highly modified landscape.

Application of Unmanned Aerial Vehicles and Thermal Imaging Cameras to Conduct Duck Brood Surveys

ABSTRACTBrood surveys are used to estimate productivity in ducks, but road‐side transects, aerial surveys, and double‐observer ground surveys have likely underestimated productivity. Duck broods are elusive and prefer wetlands with emergent vegetation where they hide at signs of disturbance, making it difficult to get accurate brood counts. Estimates of brood detection probabilities are typically below 50% and variable, which makes biological inferences about abundance tenuous. We conducted a study to evaluate the efficacy of using an unmanned aerial vehicle (UAV) equipped with a thermal imaging camera to survey duck broods in 2 study areas. In Manitoba we located 669 broods with the UAV, compared to 344 detected by double‐observer ground surveys. In Minnesota we detected 225 ducks broods with the UAV, whereas only 105 duck broods were detected by ground observers. Using a Huggins closed‐capture model in program MARK we estimated an average detection probability across both sites of 0.55 (SE = 0.02) with the UAV compared to 0.24 (SE = 0.02) for the ground crews. Although the UAV detected twice as many broods as the ground surveys, detection probability with the UAV was impacted by temperature, humidity, vegetation density, and the criteria we used to determine whether a brood could be classified as resighted. Nevertheless, using a UAV equipped with a thermal imaging camera effectively doubled the number of broods detected compared to traditional methods, and surveys were completed 3 times faster. With advancing drone and camera technology we believe UAV brood counts will become increasingly accurate and provide reliable measures of local duck productivity. © 2021 The Wildlife Society.

Impacts of oil and gas development on duck brood abundance

ABSTRACTThe extraction of oil and natural gas from reserves in the Bakken Formation has increased from 2004 to 2017 in North Dakota and northeast Montana, USA. High development areas overlap substantially with wetlands and grasslands identified as high priority for waterfowl conservation in the Prairie Pothole Region. To test for anthropogenic disturbance on waterfowl brood abundance, we conducted repeat‐visit waterfowl brood surveys during 2014–2017. We tested hypotheses about disturbance and brood abundance using hierarchical zero‐inflated Poisson models and a spatially and temporally explicit disturbance index within 3 radii (0.32 km, 0.64 km, 1.51 km). Model selection supported detection and abundance parameters that were consistent with previous research and suggested that brood abundance was higher in landscapes with high densities of small, shallow wetlands. Our analysis also demonstrated a negative relationship between abundance and the disturbance index for the smallest spatial radius (0.32 km); however, the effect size was small and predictions suggested that <1% of the broods in the sample population were affected. Considering this relatively weak negative relationship and the continued role of wetlands as the primary factor influencing brood abundance, we recommended that managers continue to focus conservation efforts in landscapes with high densities of small, unprotected wetlands, even in the presence of oil and gas development. © 2019 The Authors. Journal of Wildlife Management Published by Wiley Periodicals, Inc. on behalf of The Wildlife Society.

Sitting ducklings: Timing of hatch, nest departure, and predation risk for dabbling duck broods.

For ground‐nesting waterfowl, the timing of egg hatch and duckling departure from the nest may be influenced by the risk of predation at the nest and en route to wetlands and constrained by the time required for ducklings to imprint on the hen and be physically able to leave the nest. We determined the timing of hatch, nest departure, and predation on dabbling duck broods using small video cameras placed at the nests of mallard (Anas platyrhynchos; n = 26), gadwall (Mareca strepera; n = 24), and cinnamon teal (Anas cyanoptera; n = 5). Mallard eggs began to hatch throughout the day and night, whereas gadwall eggs generally started to hatch during daylight hours (mean 7.5 hr after dawn). Among all species, duckling departure from the nest occurred during daylight (98%), and 53% of hens typically left the nest with their broods 1–4 hr after dawn. For mallard and gadwall, we identified three strategies for the timing of nest departure: (a) 9% of broods left the nest the same day that eggs began to hatch (6–12 hr later), (b) 81% of broods left the nest the day after eggs began to hatch, and (c) 10% of broods waited 2 days to depart the nest after eggs began to hatch, leaving the nest just after the second dawn (27–42 hr later). Overall, eggs were depredated at 10% of nests with cameras in the 2 days prior to hatch and ducklings were depredated at 15% of nests with cameras before leaving the nest. Our results suggest that broods prefer to depart the nest early in the morning, which may best balance developmental constraints with predation risk both at the nest and en route to wetlands.

Assessment of repeat‐visit surveys as a viable method for estimating brood abundance at the 10.4‐km2 scale

ABSTRACTRegional estimates of duck brood abundance could help conservation managers assess landscape productivity and thereby improve spatially explicit allocation of limited conservation funds in the Prairie Pothole Region. We assessed the utility of repeat‐visit brood counts from 2012 to 2013 surveys in the Prairie Pothole Region (ND, SD, and MT, USA) and hierarchical N‐mixture models for providing estimates of abundance at a 10.4‐km2 scale. Models provided reliable estimates of brood abundance and underscored the importance of small wetlands and landscape characteristics to some dabbling duck broods in the Prairie Pothole Region. © 2018 The Wildlife Society.

The effects of cessation of fish farming on duck breeding in French fishpond systems

Fishponds are man-made aquatic systems subjected to more or less active management by fish farmers. They also are an important habitat category for waterbirds. In this study, we attempted to assess the consequences for duck breeding of fish farming interruption in a typical French fishpond region, the Forez, where fish production has declined strongly since the 1990s. Duck pair density, a brood: pair ratio and mean brood size were studied in two successive periods, 2010–2012 and 2013–2015, in 19 ponds abandoned for fish farming between 2008 and 2010, and in 34 ponds still stocked with fish among which 17 were harvested every 2 or 3 years and 17 harvested annually. Between the two study periods, a decrease in abandoned ponds was observed in diving duck (Aythya species) and red-crested pochard Netta rufina pair density and for dabbling duck (Anas species) and red-crested pochard brood: pair ratio. A possible explanation is that fish influenced the nutrient level within the aquatic ecosystem through bioresuspension of phosphorus when stirring the sediment for feeding and through nitrogen production by excretions. Decreased brood sizes in ponds still used for traditional fish farming are suggested to be the result of density-dependent predation rates.

Nest and brood stage association between ducks and small colonial gulls in boreal wetlands

Heterospecific grouping is often associated with reduced predation. One example of this phenomenon is birds breeding in association with more aggressive species. Here we report a study of the association between breeding ducks and small colonial gulls during the nesting and brood-rearing periods in boreal wetlands in Finland. Dabbling duck nests were rarely found within gull colonies, while Tufted Duck (Aythya fuligula) and Pochard (Aythya ferina) nests were exclusively found within gull colonies.During the brood stage, the broods of most duck species were found more often than expected within the colony areas of small gulls, such as the Black-headed Gull (Chroicocephalus ridibundus) and Little Gull (Hydrocoleus minutus). Dabbling duck broods in particular were associated with gulls. In diving ducks, Tufted Duck broods preferred gull defence areas, whereas Common Goldeneye (Bucephala clangula) broods did not. We suggest that colonies of small gulls may be much more important for ducks than previously thought. In recent years, Black-headed Gull populations have decreased in Finland, and the populations of Tufted Duck and Pochard have concurrently decreased.We recommend that the nesting site requirements of small colonial gulls should be taken into account in wetland restoration and when building new wetlands.

Temporal variation in pond use and breeding success for ducks in French fishpond regions: on possible consequences of a decline in fish farming

Fish farming abandonment or extensification may theoretically lead to contrasting consequences for waterfowl breeding in fishpond complexes. We investigated the variation of four indices of duck density or breeding success in pond samples of three main French fishpond areas: Dombes, Forez and Brenne, along with recent changes in fish farming management. In Forez, where fish stocking has been frequently interrupted or fish biomass in ponds has substantially decreased during the two last decades, duck pair density strongly increased in the same time interval, but Mallard Anas platyrhynchos brood size decreased. In Brenne, no fish farming abandonment was observed but pond fertilization with organic manure or mineral nitrogen became less frequently implemented during the 2000s. The duck brood: pair ratio decreased meanwhile, indicating either a lower nesting success or higher losses before or immediately after hatching. In Dombes, lower fish stock densities since the 1990s did not reverse a negative trend in duck populations which started in the early 1980s. Our results suggest that fish biomass density in fishponds might be a limiting factor for breeding waterfowl, but a decrease in the nutrient level, for example with lower fertilizer inputs, may negatively affect duck reproductive success.

Wetland use by brood‐rearing female ducks in a boreal forest landscape: the importance of food and habitat

Habitat use by birds may be related to single or interacting effects of habitat characteristics, food resources and predators, but little is known about factors affecting habitat use by wetland species in boreal ecosystems. We surveyed brood‐rearing females and ducklings of four common boreal duck species to assess the effects of habitat structure and food resources on the use of wetlands by brood‐rearing ducks. Although wetland use by duck broods was related to habitat structure and food abundance, their relative importance varied among duck species. For theCommonGoldeneyeBucephala clangula, a diving duck, aquatic invertebrates and large emerging insects were the most important factors associated with wetland use.CommonTealAnas creccabroods were observed more often on wetlands with greaterDipteran emergence, whereas inMallardAnas platyrhynchosboth habitat structure and large emerging insects were important. The occurrence ofEurasianWigeonAnas penelopebroods was related to emergingDiptera and habitat structure but the associations were not strong. The varying habitat and food requirements of common duck species could influence the success of wetland management programmes, and consideration of these factors may be particularly important for initiatives aimed at harvested species or species of conservation concern.

Distribution of duck broods relative to habitat characteristics in the Prairie Pothole Region

AbstractConservation programs for breeding ducks in the Prairie Pothole Region (PPR) of the United States and Canada require effective means of evaluating and characterizing breeding habitat across large landscapes. Extensive surveys of the distribution of duck broods in late‐summer could help identify wetland basins with greater probabilities of occupancy. Broods are difficult to detect, however, rendering presence–absence data from single‐visit surveys difficult to interpret, particularly when probability of detection is related to habitat features. Multiple‐visit occupancy surveys offer a potential solution. From 20 July to 5 August 2007–2009, we conducted a 3‐visit survey of wetland basins located on 167 10.4‐km2 study plots in the PPR. Our survey focused on broods of the 5 most common breeding duck species (Anas spp.). Our main objectives were to investigate ecological relationships between occupancy of wetland basins by broods and habitat characteristics and to examine if habitat‐specific detection was of enough concern to warrant multi‐survey approaches in the future. We surveyed 3,226 wetland basins during the study. Probability of occupancy of a wetland basin by a brood was positively related to the log of wet area for all 5 study species and was greater on wetlands located on plots with a greater proportion of herbaceous perennial cover for 4 of 5 species. For example, the median probability of occupancy for gadwall (Anas strepera) increased from 0.08 (90% Credible Interval [CrI]: 0.07, 0.10) to 0.28 (90% CrI: 0.23, 0.33) as wet area increased from 0.19 ha to 2.12 ha, and increased from 0.12 (90% CrI: 0.09, 0.16) to 0.20 (90% CrI: 0.16, 0.25) as proportion of perennial grass cover on the study plot increased from 0.03 to 0.99. Because occupancy and detection were both related to attributes of wetland basins, we concluded that the multiple‐visit survey was a useful approach for identifying habitat relationships of duck broods. Our results indicated that most broods of the study species were found in 10.4‐km2 landscapes with greater densities of small‐ to mid‐sized wetland basins and a greater proportion of herbaceous perennial vegetation. Our study provided new empirical support that could be used to help target conservation actions to the most productive landscapes for breeding ducks. © 2012 The Wildlife Society.

Influence of fish-farming management on duck breeding in French fish pond systems

Fish ponds host a relatively important share of the breeding population of waterfowl in Europe. The objective of this study was to investigate the influence of fish-farming management on the distribution of dabbling and diving duck breeding, in 103 fishponds from four regions important for duck breeding in France. Duck breeding in fish ponds was apparently influenced by food resource and nesting site availability. Dabbling duck pair density was generally higher when invertebrates were abundant in macrophytes beds and when competition for food with carps Cyprinus carpio was potentially decreased by lower fish stock biomass. Diving duck pair abundance seemed to be negatively influenced by low invertebrates biomasses in pond sediment and by the absence of large reed beds at the edge of waterbodies. The difference between dabbling and diving ducks was also confirmed by a study of the variation in brood numbers standardized by pair numbers. This brood:pair ratio corresponded to a measure of nesting success and the possible attraction of fish ponds for some broods hatched in neighbouring waterbodies. Dabbling duck brood:pair ratio was lower in one of the study regions where most of meadow areas surrounding fish ponds have been transformed into cereal crops in the past few decades. Diving duck brood:pair ratio was positively linked to pond fertilization due to fish farming. Fish farming, therefore, influenced duck breeding by an interaction between carp density and fertilization. We hypothesize that fertilization increases zooplankton density, thereby decreasing the competition between carps and waterfowl for benthic prey.

POST-FLEDGING BROODS OF MIGRATORY HARLEQUIN DUCKS ACCOMPANY FEMALES TO WINTERING AREAS1

Abstract We describe evidence that Harlequin Duck (Histrionicus histrionicus) broods accompany their mothers from breeding streams to coastal molting or wintering areas. Observations indicated that all surviving female-offspring groups left breeding areas together. We later sighted some family members at the coast near each other, suggesting that they had arrived together, then separated. We observed family groups at wintering areas in August and September. Family groups tended to separate quickly, although some family members maintained contact for over five months. To our knowledge the evidence we provide is the first suggesting that female migratory ducks bring their offspring to wintering areas, a pattern similar to geese and swans. This may be facilitated by an unusual strategy of wing molt, in which Harlequin Ducks molt after migrating to wintering areas. Due to winter pairing and strong philopatry in Harlequin Ducks, migration of families may contribute to genetic differentiation among populations.

Temporal distribution of waterfowl in eastern South Dakota: Implications for aerial surveys

Abstract The U.S. Fish and Wildlife Service and Canadian Wildlife Service incorporate information from annual aerial and ground counts of waterfowl into harvest management strategies. Timing of population surveys is thought to be optimal for early nesting species but may not reliably reflect the status of species with later migration chronology. The purpose of this study was to evaluate effects of survey timing on diving duck and duck brood abundance indices in eastern South Dakota. Findings indicate that timing of aerial breeding surveys occurred too early in eastern South Dakota to accurately reflect diving duck population status because birds had not yet settled into breeding habitats and aerial production surveys did not coincide with peak duck brood abundance. Diving duck abundance from aerial surveys conducted during 10–17 May were higher than indices from ground surveys conducted 2 weeks later because lesser scaup (Aythya affinis), ring-necked duck (Aythya collaris), and bufflehead (Bucephala albeo...

Wood Duck Brood Movements and Habitat Use on Prairie Rivers in South Dakota

Wood duck (Aix sponsa) populations have been increasing in the Central Flyway, but little is known about wood duck brood rearing in prairie ecosystems. We compared movements and habitat use of radiomarked female wood ducks with broods in South Dakota on 2 rivers with contrasting prairie landscapes. The perennial Big Sioux River had a broad floodplain and riparian forest, whereas the intermittent Maple River had emergent vegetation along the river channel. Movements between nest sites and brood-rearing areas were longer on the Maple River than on the Big Sioux River (P = 0.02) and were among the longest reported for wood duck broods. Movements on the Big Sioux River were longer in 1992 (P = 0.01), when the floodplain was dry, than in 1993 or 1994. Before flooding occurred on the Big Sioux River, broods used semipermanent wetlands and tributaries outside the floodplain; thereafter, females selected forested wetlands along the river. Broods on the Maple River used emergent vegetation along the river channel throughout the study. Because median length of travel to brood-rearing areas was 2-3 km, we recommend maintenance of brood-rearing habitat every 3-5 km along prairie rivers. Wildlife managers should encourage landowners to retain riparian vegetation along perennial rivers and emergent vegetation along intermittent streams to provide brood-rearing habitat during wet and dry cycles.

RESULTS OF RADIO—TRACKING OF DUCKS IN THE LAKE ENGURE IN SUMMER 1997

ABSTRACT In summer 1997 a project of duck research using radio—telemetry was carried out on the Lake Engure, Latvia. 10 females of Mallards, 10 females of Shovelers, 9 females of Pochards and 6 females of Tufted Ducks were radio—tracked during the period from the hatching of their ducklings till fledging. Information about effect of the harness-type radio-transmitters on different species of ducks has been collected. For 15 ducks home range sizes and distances between nests and range locations were calculated. Mallards used to move further from their nest sites; one Mallard brood after one week spent near the nest site dislocated 8 km to the Southern part of the lake during one day. Problems of estimating habitat use and habitat selection of duck broods have also been discussed.

Significance of invertebrate abundance to dabbling duck brood use of created wetlands

We investigated factors influencing dabbling duck (Anas spp.) brood densities on 9 created wetlands, arranged in 4 clusters on the National Elk Refuge in western Wyoming. Because dabblers are limited by the depth they can reach while up-ending, and created wetlands were between 1.5–2.5 m deep, we examined the significance of invertebrate density in the top 25 cm of the water collumn and in the entire water column where brood use occurs. Total invertebrate, nekton, and zooplankton density in the entire water column measured in 1992 accounted for between 59%, 61%, and 73%, respectively, (P<0.05) of the variation in brood density among wetlands that year. No variable measured in the top 25 cm of the water column accounted for variation in brood densities on wetlands. We suggest that vertical migrations in the water column make most invertebrates accessible to dabbler hens and broods.

Habitat-related variation in movements and fledging success of American black duck broods in northeastern Nova Scotia

Female American black ducks (Anas rubripes) are known to move their broods from low- to high-nutrient rearing sites. We studied the extent of brood movement and fledging success in a northeastern Nova Scotia watershed. Annually, about half the broods moved either overland or along three rivers from small, widely dispersed oligotrophic–mesotrophic wetlands to a large hypertrophic tidal marsh. Mean brood size at fledging was 3.50 in the tidal marsh but 7.05 at the dispersed freshwater wetlands. Females that remained at dispersed sites fledged more ducklings than females that moved to the marsh. Attrition occurred predominantly in the marsh or in transit. Females fledged fewer young when they raised broods at the marsh than when the same females raised broods at inland sites. Females were as successful at nutrient-poor sites as at nutrient-rich sites. The study suggests that concentrating birds in nutrient-rich sites may be counterproductive in terms of female reproductive fitness and population recruitment.

Habitat use by different‐aged duck broods and juvenile ducks

Habitat use by different‐aged broods and juveniles of teal Anas crecca, mallard A. platyrhynchos and goldeneye Bucephala clangula was investigated in southern Finland during 1988–1993. The study focused on within‐lake habitat use and the use of flooded wetlands. Downy ducklings of all three species showed significant preference for Carex‐stands. As the dabbling ducks grew older, their habitat use diversified, juveniles in particular also made considerable use of floating vegetation. Conversely, habitat use by goldeneye became more uniform: goldeneye juveniles were almost exclusively seen in open‐water and floating vegetation habitats. All three species, but especially teal, used flooded areas intensively. Two thirds of teal downy broods were seen along flooded shores which comprised only seven percent of all shore habitats. Preliminary data suggested that the preferred habitat types, Carex and flooded shores, harboured more nektonic invertebrates and emerging insects than did the other shore types.

Use of lakes by black duck broods in relation to biological, chemical, and physical features

Characteristics of 32 freshwater lakes in central and western Nova Scotia were quantified to determine the relative influence of various biological, chemical, and physical factors on habitat selection by black ducks (Anas rubripes Brewster) during brood-rearing. Acidity and trophic status varied greatly among the waterbodies, of which 20 were used by black ducks for rearing their young. Duck brood density was positively related to lake trophic status. The highest brood densities occurred on hypertrophic waterbodies with a large anthropogenic input of nutrients.

Effects of Saline Water on Growth and Survival of Mottled Duck Ducklings in Louisiana

We studied the effects of saline drinking water on the growth and survival of penned mottled duck (Anas fulvigula) ducklings at Rockefeller Wildlife Refuge in southwestern Louisiana in 1989. Duckling mortality at different salinities was 100% at 18 ppt, 90% at 15 ppt, and 10% at 12 ppt. No ducklings died within treatments of <12 ppt, but the growth rate of ducklings in the 12-ppt treatment was lower (P _ 0.05) than all lower salinity treatments. When ducklings were given 12-ppt salinity water and exercised, mortality would have exceeded 70%. Initial lethargy shown by ducklings in the 9-ppt treatment, combined with potentially high mortality of ducklings given 12-ppt salinity water and exercised, suggested that the upper salinity threshold tolerated by wild mottled duck broods lies within this range. We advocate creation and management of semi-impoundments in coastal Louisiana and Texas to prevent deterioration and/or loss of marshes of <9-ppt salinity to provide quality habitat for mottled duck broods and other species of flora and fauna dependent on these marshes. J. WILDL. MANAGE. 55(3):471-476 The mottled duck is a nonmigratory species occupying a restricted range in North and Central America. Isolated populations occur in Florida, central Mexico, and the coastal marshes from Mississippi westward to northern Veracruz, Mexico (Bellrose 1980). However, the greatest number (98%) of mottled ducks occurs in coastal marshes of Louisiana and Texas where there is an estimated breeding population of 110,000 (Stutzenbaker 1988). There is concern about the mottled duck because annual surveys conducted in Louisiana have indicated a 44% decline from 1971 to 1983 (Stutzenbaker 1988). Stutzenbaker (1988) hypothesized that the loss and deterioration of remaining habitat in both Texas and Louisiana might be responsible. Saltwater intrusion, in particular, has caused significant habitat changes in Louisiana marshes. From 1968 to 1978, for example, freshwater marsh vegetation decreased and saline vegetation increased, especially in areas transected by large canals (Chabreck and Linscombe 1982). Furthermore, saline drinking water may affect the condition of both adult and juvenile waterfowl (Windingstad et al. 1987, Tiejte and Teer 1988). Ducklings are even less tolerant of salt water than adult birds because their salt glands are poorly developed, especially at <6 days of age (Ellis et al. 1963, Schmidt-Nielsen and Kim 1964, Riggert 1977). Mallard ducklings, for instance, suffered mortality, reduced growth, and a variety of sublethal physiological abnormalities when exposed to high concentrations of sodium sulfate, magnesium sulfate, and saline water occurring in natural wetlands in Saskatchewan (Mitcham and Wobeser 1988a,b). In North Dakota, wild ducklings concentrated and fed around freshwater seepages on saline lakes (Swanson et al. 1984). Female mottled ducks often bypass less productive areas of marsh close to the nest while leading ducklings to more productive broodrearing areas (Baker 1983). Therefore, ducklings traveling through, or remaining in, marshes affected by saltwater intrusion could suffer decreased survivorship. Our study determined the effects of saline water on the growth and survival of mottled duck ducklings. We hypothesized that survivorship, growth rates, and levels of body mass and carcass components would decrease as salinity levels increased. Financial support was provided by private corporations and landowners concerned with wetland management in the Louisiana coastal zone. We are extremely grateful to R. G. Vincent, Jr., from the Miami Corp., B. N. Kirkpatrick from the J. G. Gray Estate, W. P. Hardeman from the Amoco Production Co., J. P. Donohue from the Vermilion Corp., T. Wright from the Sweetlake Land and Oil Co., and J. Woddard from the FINA Oil and Chemical Co. J. T. Joanen and W. G. Perry provided assistance and ideas throughout the study. W. M. Shields and L. W. VanDruff reviewed the manuscript, and