USGS - science for a changing world

Northern Prairie Wildlife Research Center

  Home About NPWRC Our Science Staff Employment Contacts Common Questions About the Site

Assessing Breeding Populations of Ducks by Ground Counts


Compiled by J.B. Gollop

The following is a summary of the all-day discussion which took place on February 22, 1967. It must be remembered that discussions differ significantly from prepared papers in at least two ways: (a) there is no opportunity to document statements, and (b) because a number of people are making spontaneous remarks, there is little organization. Furthermore, since the following is a summary and contains no direct quotations, there is always the possibility of misinterpretation on the part of the summarizer (for which he apologizes if it has occurred). Statements should, therefore, be treated with some caution and confirmation or additional information should be obtained from the participant credited.

The sequence of subjects and of statements presented below bears no resemblance to the sequence in which they were given. In some cases, a person's comments have been broken into two or more parts in an attempt to improve continuity. In other cases, remarks made at various times through the day have been combined. No attempt has been made to present details of data that were projected or otherwise displayed; in most cases the data were from papers given earlier in the seminar. It should be noted that what may appear to be irrelevant comments in the summary below were, in fact, relevant at the time they were made, possibly in answer to a question. More people took part in the discussion than is indicated below; seldom have questions been included even though they initiated discussion at the time. Also, most of the Chairman's remarks in his continuing summaries and his encouraging of further discussion have not been included. In a few cases the recording was not adequate for transcription.

Pond water (water quality, pesticides, over-fertilization)

Nelson: The U.S.F.W.S. water quality program started in 1966 in the Dakotas is checking residues in ponds and if something that causes alarm shows up, further attention will be given to it. Bossenmaier: Water samples from the Assiniboine River are being compared with Lake Manitoba so that predictions can be made to determine the effects of the river diversion on plant and animal life. Pesticides are probably not included.

Jahn: J. J. Hickey, University of Wisconsin, did some work in Lake Michigan where pesticides had been washing into the lake from orchards for some time. He found that residue concentrations increased from mud to water to invertebrates to fish to gulls, where concentrations were such that they should be of concern. Such a progression is probably similar in ducks. Certainly old-squaws on Lake Michigan have high pesticide residues. Smith: There has been some collecting of duck eggs for pesticide analysis from the Arctic through the western breeding grounds. Pesticides occurred at somewhat similar levels in samples from all areas. Apparently this was done for only one year. Nelson: One problem was that the roadside at Yellowknife, Northwest Territories, had been sprayed. Crissey: Wings from the wing survey are being used to monitor pesticides.

Hammond: A major problem on the Souris River, North Dakota, is that sewage is sufficient at certain times of the year to produce excessive amounts of phosphorous and nitrogen resulting in algal blooms which adversely affect pondweeds and pondweed seed production. Smith: The algae Aphanizomenon, an indicator of high phosphorous levels, was found in a 5-acre pond, probably the deepest pond at Lousana, Alberta, in an overgrazed grassland pasture. The most noticeable difference between it and other ponds were algal blooms and leeches; there was also a high watermite population. Jahn: One example of intensive management to overcome over-fertilization: Dairy cattle farmers around Lake Mendota, Wisconsin, deposited manure on the snow in winter; nitrates and phosphates were washed into the lake in spring and, consequently, aquatic plants were shaded out by algal blooms. Soil conservationists recommended that each farmer build a cement pit (since subsidized), put the manure into it through the winter, and in spring spread it on the land so that nitrates and phosphates could percolate into the soil. Crissey: What is happening to prairie potholes as a result of grasshopper spraying?

Pond invertebrates (sampling done, food habits)

Nelson: Early work of John Moyle in Minnesota is probably some of the more definitive in relation to ponds. Ray Murdy collected invertebrate samples on the Yellowknife study area; these are being analysed by the Smithsonian Institute now. U.S.F.W.S. Northern Prairie Wildlife Research Center, Jamestown, North Dakota, has a limnologist who will work with their chemist and others on water quality of small wetlands. Techniques are a problem. Drewien: Some invertebrate collections were made on stockponds in South Dakota. Millar: C.W.S. had a limnologist originally on their wetland classification study areas. He did some collecting of invertebrates but did not analyse the samples. He concentrated on water chemistry. A graduate student in the Geology Department, University of Saskatchewan, did a study of the Ostracods of these ponds under C.W.S. contract. He concluded that he could classify sloughs at least as to whether they were permanent or semi-permanent on the basis of the Ostracods. As of April 1 we will have a position for a limnologist to work on small ponds. Smith: Water and soil samples were collected at Lousana in May and July near the shore line and centre of Type 3, 4, and 5 ponds in four localities one year. The next year collections were made from other ponds of the same types. Invertebrates were collected by pouring 10(?) litres of water through a screen. They were identified by genera. Mud samples were found to be unsatisfactory. No conductivity tests were made. Invertebrate densities were found to be highest in ponds that had been dry for 1 or 2 years and were then flooded. Crissey: An indication of the effect of rejuvenation of dry basins by flooding might be the Minnedosa, Manitoba, area in 1959 and 1960: in 1959 everything around was dry but Minnedosa was wet and had a lot of birds. In 1960, Minnedosa looked excellent and the surrounding area had only a little water but there were only scattered pairs through the Minnedosa area while the adjacent district had many birds. It appeared that Minnedosa which had held water for several successive years was much less attractive than habitat that was dry in 1959. Jahn: This is a natural example of an established ecological principle that a draw-down is necessary to convert nutrients into a form that plants can use.

Stoudt: Some semi-permanent areas are good duck producers if sufficient shore is bared periodically. Other areas are fertilized by an outside source such as farmyard manure, rain, or siltation. Nelson: Ground-water may also be a factor. Hammond: Jim Salyer worked on two sloughs near Loxford, North Dakota. One was fresh and spring fed and the other was semi-permanent. Invertebrates and water chemistry were quite different. Neither was ever used by broods. Millar: A pond that is cultivated and then flooded again is as productive as it was originally, except that aquatic plants take some time to return. Jahn: John Ferguson once made the point that fluctuations in invertebrates are not important to ducks. The important thing is what is present and how much at particular stages of a bird's life cycle. Therefore, periodic sampling should produce results that can be expressed in square or cubic units. Sampling is more critical for absolute than relative values. Paired samples should be collected from ponds occupied and unoccupied by breeding ducks. This may result in an evaluation of the potential for occupancy. If foods are similar, then another factor, e.g., spacing mechanism or shortage of ducks, should be investigated. Smith: Invertebrates were found to be similar in occupied and unoccupied ponds at Lousana.

Stoudt: As part of a Ph.D. thesis, Jim Bartonek did a food habit study of canvasbacks at Minnedosa which included collections of bottom samples, chemical analyses, etc., of four ponds. Nelson: Also included were attempts to correlate abundance of invertebrates with plant and water characteristics. Jahn: Chura found that mallard ducklings in Utah lived primarily on invertebrates for their first 3 weeks. Stewart: The downy young of black ducks on the east coast feed almost entirely on widgeon grass seeds. Gollop: N.G. Perret did a Master's thesis at Minnedosa on the food of adult and young mallards and its availability. Crissey: Was not one of Perret's conclusions that invertebrate populations changed more from day to day or week to week than from pond to pond? There is also the effect of daily and weekly fluctuations in the volume of water due to drying and to showers on plants, animals, and minerals. Stewart: As water levels drop, salinity and specific conductivity increase; plants and probably invertebrates are affected.

Pond numbers (techniques for determining numbers)

Crissey: Air crews are instructed not to count road ditches, temporary water, and muskeg, but interpretation is a problem between crews. A water area survey in late June or early July might be done in less than 10 days, possibly at an altitude of 4,000-5,000 feet, using wider and fewer strips than current July surveys. July pond counts are biased by rain streaks. Photographs may not be practical for determining water area data across the Prairie Provinces because of the possibility of cloud cover during the comparatively short time when the survey should be conducted and because of the time required to interpret the photographs. Apparently there is little difficulty in determining from the air whether there is water in a vegetation-choked pond. Millar: It may be impractical to detect water by direct aerial observation in choked ponds some distance from the aircraft. Infra-red film does not show water through solid emergent cover. Goodman: Jets at high altitude may overcome this. Crissey: It is a problem if Armed Services must be relied on for annual operations. Stephen: Other equipment, regardless of current cost, should be investigated, e.g., radiation detection devices which might eliminate the need for photography.

Crissey: Don Hayne has prepared a report on a preliminary investigation using precipitation to predict the number of May ponds. Based on an analysis of (a) total precipitation from the previous June through the current May and (b) total precipitation from August 2 years previous through the previous May, he obtained a fairly good fit between predicted and measured numbers of May ponds for many waterfowl strata from 1951 to date. A looser fit between predicted and measured May ponds was obtained from an analysis of (a) the number of ponds counted the previous May and (b) the precipitation expected between the summer period and the following May when ponds were counted again. There is a different formula for each stratum. While not adequate as yet, the method is worthy of further investigation. Millar: Problems are more complicated with specific sloughs within an area and between areas because of local precipitation, frost seal, runoff conditions, etc. Stoudt: Tree-ring data for about 400 years in North Dakota suggest that predictions based on the previous year's precipitation are not possible. Crissey: If a system has a sufficient degree of compensation built into it (and this may be one) that it gives reasonably accurate totals for a stratum or for the entire prairies, it can be used.

Breeding pair surveys (techniques for ground work)

Hammond: Ground census methods used in the north-central plains for ponds and large marshes are described in the manual of instructions included as Appendix 1. On surveys it is important to record minutely in the field to allow for versatility or standardization in combining data in the office. There is need for precise definitions of environmental factors and standardized methods for recording them from one ecological investigation to another.

Dzubin: As a rule of thumb, the optimum time to census a population is when one-third occurs as pairs, one-third as lone drakes, and one-third as grouped drakes between 0800 and 1200 hours, at Kindersley, Saskatchewan, at least. There is approximately a 5-day period in any given area when a single census might be valid for all common Canadian prairie species. A dual nesting peak makes it very difficult to gain an appreciation of a species' breeding cycle. Counts of only pairs and lone drakes result in below-actual breeding population. All grouped drakes should be counted as pairs up to a certain date which varies from species to species. Omit lone hens of major species in a census because they constitute an insignificant portion of the breeding birds seen (at Kindersley) and because their drakes have probably been counted. This may not be so for uncommon species. Small groups of unmated male canvasbacks may remain in a district into June thus complicating breeding pair counts. On the other hand, the situation is further complicated if they remain less than a week: a sex ratio determined while they are there for application later in the year to what may then, in fact, be only mated drakes, would produce erroneous figures.

Smith: Duplicate counts were probably insignificant on the 29-mile transect at Lousana, because birds were carefully "watched down" when flushed. Hammond: At Lostwood Refuge, North Dakota, six-square-mile blocks were censused by strip transects with several hours between adjacent transects so that birds had an opportunity to redistribute themselves. This probably reduced duplicate counts. Hawkins and Goodman: In pothole country and on large marshes birds tend to land near the point of flushing, although in pothole country, at least, they may fly for 10 minutes before doing so. Dzubin: Counts made at mid-day are less likely to flush birds, thus avoiding duplicate counts. Home range research is needed. With colourmarked birds, 12 home ranges of mallards were delineated in 8 years. With telemetry, a similar quantity of data might be obtained in a few weeks. Drewien: Twelve home ranges of a relatively immobile species, blue-winged teal, were delineated in 2 years in South Dakota. Dzubin: Telemetry is not expensive when relative amounts of time for equal and adequate amounts of data are considered. Jahn: Other workers recommend that initially the outlay of money for telemetry projects should be large enough to obtain adequate samples, that clear-cut, specific problems be studied, and that data should be analysed after 3 years.

The problems of ponds along transect boundaries, nest vs. duck counts on small blocks of land (e.g. 2 square miles), strip vs. block study areas, ingress of pairs, and broods equalling egress were also discussed with evidence of varying opinions and no solutions.

Stoudt: Selection of type and location of study area should be based on objectives and should consider problems arising from special situations, e.g., in South Dakota, a study area in the Coteau where water is much more permanent than in the adjacent drift prairie where sheet water is common, is likely to have an influx of mallards and pintails as the sheet water dries up.

Breeding pair surveys (biases in aerial work, air-ground comparisons)

Crissey: Some of the biases in air surveys are: (a) proportions of broods seen by air crews in early morning may be double those seen at mid-day (Smith: Morning sun has a predominance of yellow rays accentuating colours; red setting sun tends to turn colours black); (b) differential visibility: green-winged teal lowest, canvasback probably highest; (c) personal biases, e.g., eyesight, proportions identified, transect width, fatigue, experience; (d) direction of flight; (e) weather (fog and wind); and (f) habitat, although grassland and parkland differences may be less significant than once thought, partly because of magnitude of other biases. Nelson: In one experiment the pilot's efficiency was similar to the observer's during the first hour, 80 per cent of observer's at end of second hour, and 70 per cent after 4 hours; there was no measure of observer's relative efficiency. Crissey: In another case one person, both as pilot and as observer, saw 17 per cent more birds than the other crew member. This was apparently related to proportions identified, although species composition was similar for both. It is assumed that unidentified ducks have the same characteristics (species, pairs, lone drakes, and flocks) as identified birds. If not so, this would be an important bias if observers were not equally able to identify all species. In one case it required 10 days for a new observer to arrive at a species composition similar to an experienced pilot's although results were unknown to either at the time. Smith: Experience reduces fatigue; usually 4 hours at a time is sufficient although 8 hours have been flown in emergencies.

Crissey: The solution to date for determining the proportions seen and identified by air crews has been to lay out 31 east-west ground beat-out transects across the prairies. Each transect is long enough to contain between 100 and 300 potholes. Air surveys are usually started when blue-winged teal arrive and break up into pairs. In each of the Prairie Provinces, air crews are asked to fly 10 strips four times each in the same manner as regular transects. This is probably the maximum amount of time operational air crews can afford during surveys. Ground crews were to cover the same strips once within 2 days of air coverages. It has been assumed that ground crew pair data are highly accurate, preferably 100 per cent. There are usually fewer birds recorded on the second of two aerial coverages than on the first, but the direction of flight of the first coverage particularly in the morning, affects such results Apparently it is impossible to take out the effect of such factors as time of day, direction of flight, sun, wind, experience, etc., by statistical methods and current data. Straight statistical analysis indicates a very high variability, suggesting that the data are unusable. However, the variability may, in fact, be a measure of the magnitude of change actually occurring on operational transects. This conclusion is suggested because application of visibility factors to observed mallard breeding populations, followed by calculations of production, kill, and other mortality, results in an estimate of the mallard breeding population the following year which is close to the visibility-adjusted figure actually obtained in May of that year.

Crissey: These transects are not as representative as is desirable; they have higher than average densities of ponds and there is evidence that density of ponds is inversely related to the proportion of birds seen by air crews. In theory, therefore, visibility rates based on those transects should be too low for the prairies as a whole. However, since they produce usable results, it may be that this bias (high density) is being balanced by unconscious (or otherwise) concentration of air crews when flying test strips. Air crews need not be advised of locations of test strips but in this case many more ground transects would have to be beat-out to get the quantity of data currently obtained by four aerial coverages of a single strip. Few segments of operational air transects can be worked by road.

Cooch: In 1966 the R.C.A.F. flew a ground-air transect in Manitoba at mid-day in a strong wind at 600, 1,200, 1,800, and 5,000 feet, with infra-red, black and white, and camouflage film. None of the 140 ducks known to be present was visible on film. A computer scanner may be suitable for counting water areas. Crissey: Work to date indicates that a helicopter probably does at least as good a job as a ground crew, and a helicopter could check ponds on operational transects. However, it would probably require one helicopter per crew for adequate data. It is too slow to do operational surveys by helicopter beat-out. Nelson: A 7- to 10-day course for standardization of ground and air techniques was initiated at Jamestown in 1966.

Pairs and ponds (carrying capacity and limiting factors)

Crissey: There is evidence that mallards (and other species) overflew the prairies and went to the Northwest Territories and northern Alberta in 1959, 1961, 1962, and probably in other years. This indicates that the prairies were at carrying capacity even though some areas were unoccupied, possibly because of the small number of poor quality ponds. The quality of potholes may be lower when potholes are fewer, e.g., brood mortality may be increased if ponds dry up; an abnormally high May: July pond ratio may depress renesting. Research is needed to determine what water or other habitat factors attract birds to an area. Cooch: The relationship between ducks overflying the prairies and wetlands on the prairies is more easily understood if northern populations are given as percentages of continental populations rather than as absolute numbers, and if conditions on the prairies are expressed as ducks per pond rather than numbers of ponds. Stewart: In North Dakota, the number of breeding pairs per 100 acres of water was fairly constant every year regardless of the number of potholes, indicating that ducks fill North Dakota potholes to carrying capacity each year. Stephen: Except for years of extremes in production, water quality is generally not a significant factor to ducks. Smith: Water surviving until July may be a measure of annual water quality for ducks and currently this cannot be determined across the breeding grounds in May.

Specific examples of duck movements during the breeding season were given: pintails to Eskimo Point, Northwest Territories, in 1961 (Cooch); redheads and ruddy ducks into North Dakota in late June 1962 (Stewart); green-winged teal or pintails to Tule Lake, California, in 1959 (Crissey); various species into Nebraska and South Dakota in 1958 and 1959 (Hammond). Hawkins: It cannot be assumed that delayed breeding is always related to habitat. Lead poisoning which varies in importance from year to year may be an influence.

Hammond: Data from 1965 indicated that depth of a pond (related to permanency) did not greatly influence pair use within a size class. Diameters of circular ponds under 2.5 acres may be correlated with pair use; shore line may be a more important factor on larger sloughs and elongated ponds. The occupancy of channels or narrow sloughs is significantly influenced by width: 250-300 feet may be a minimum width for occupancy of both sides by blue-winged teal.

Pairs, ponds, and production

Crissey: Based on a correlation between production and July ponds, air crews are apparently counting water areas in May that are not important to what happens to the ducks. If there were an adequate correlation between May ponds and production, it might be that two surveys in May (one for ducks and another for ponds) would suffice for continental predictions of fall flights. Cooch: One of my two methods of predicting production is based on the premise that May water is required to disperse birds and July water to raise them. The other method involves May ducks, May ponds, and a factor in the order of 2 or 3 varying with the segment of the breeding grounds involved. Stewart: Some of the very best ponds for breeding pairs are seasonal ponds that are dry by July. A late May or early June count might be the solution. Crissey: On the other hand, the data suggest that many more very small temporary ponds are being counted that do not really make any difference to pairs. In a year when there is wide difference between May and July pond counts, i.e., wetlands are rapidly disappearing, production is probably less successful than when the two water counts are closer. There may be an adverse effect on renesting in the former case. On the other hand, during a series of drought years, drought apparently did not decrease quality enough to upset the formula for predicting age ratios. Cooch: Pond-production predictions are better when production is good, suggesting that water quality may be involved. Stewart: The number of pairs in North Dakota was much more closely related to the acreage of water than to the number of ponds. Smith: This relationship may be influenced by average pond size.

Smith: Because of experience on the site, it was possible to predict production, based partly on intangible factors in late April and early May, in 8 years out of 10 at Lousana. Hawkins, Stoudt: The same was possible for workers familiar with Minnedosa, Manitoba, and Redvers, Saskatchewan. Crissey: If a count of effective May water, i.e., the water actually attracting breeding populations, could be obtained, such predictions might be possible prairie-wide, particularly for mallards. It is possible that using well-scattered paired samples of pond counts, the percentage change between years could be detected with much less flying than is now being done in July. Rounds: Preliminary feasibility data may be available from aerial segments.

Harvest unit management philosophy (adult and young migrations and homing to breeding areas)

Crissey: Are harvest units up and down flyways really separate from other units and manageable? Based on direct recovery rates, the Central Flyway feels that the High Plains mallards of Colorado are underharvested. Therefore, they are requesting a larger harvest on the grounds that it will have no effect on any other harvest unit. This depends in part on whether the distribution of young is similar to the distribution of their parents. Nelson: Winter banding in that area traps a high proportion of adults. Crissey: Data examined to date suggest that young distribute themselves independently of their parents. If this is so, reduction of a population from one portion of the wintering area will affect harvest the next year over a wide area. Telemetry may provide part of the answer. A U.S.F.W.S. project has been proposed to put 1,000+ radios on hen mallards in northwest Colorado in February or March and in July locate them and band their young. Adult females can be expected to return to the wintering area where they were marked but indications are that the young will fan out in all directions. Although young may not follow their parents, it is still possible that the distribution of all adults from a portion of the breeding grounds may influence the distribution of the young in total. If this is true, then harvest units may constitute independent entities and the number of young returning to a particular harvest unit will be related to the number of adults returning and would not affect other harvest areas. This also affects the flyway concept. At one time the irrigated Columbia Basin in Washington was wintering one-fifth of North America's mallards. This build-up was due, at least in part, to low vulnerability (large water, feeding outside shooting hours) and high survival rate. Regulations were liberalized to keep that population from building or even to knock it back. Did this also reduce flights from southern Alberta going to the Central and Mississippi Flyways?

Lacy: Is it possible that an increasing Columbia Basin mallard population could displace Mississippi or Central Flyway birds in limited breeding habitat and force Eastern Flyway birds to breed in less favourable areas, thus reducing fall flights to those flyways? Crissey: Harvest rates on these birds have increased with more liberal regulations and new hunting techniques.

Gollop: From five Kindersley mallard broods for which there were two or more recoveries each, we know that in two cases brood mates were found on opposite sides of the Rockies and in a third case two members of one brood were recovered in Florida and Texas in December. The distribution of direct recoveries from one slough was similar to that from the entire degree block-across all four flyways. On three occasions adult hens, moulting or with broods, from the same slough have been recovered in the Pacific and Mississippi Flyways in the same week. There are differences in the temporal distribution of early hatched and late hatched mallards. More adult than young mallards were recovered in the Pacific Flyway, which may reflect hunting pressure or relative survival. Hawkins: Manitoba data give similar indications. Jahn: Is there a critical distance between natal marsh and breeding site for a young duck? Frith's work in Australia indicates that ducks take advantage of suitable breeding habitat wherever it occurs and, therefore, they probably have few ties with natal areas. Does this also apply to ducks in the Prairie Provinces? Crissey: The first year that an area is wet after being dry for a long period it is filled by birds that could not possibly have been reared there and probably had never bred there. It would be interesting to determine from wings whether the ducks appearing in such areas are yearlings or older. Hawkins: Wood ducks with almost constant breeding habitat home precisely.

Brood identification

Jahn: Is there need for a brood identification guide for game managers? Stoudt: It is best to flush hens for identification; there is considerable difficulty with canvasback-redhead identification when downies are in the same brood. Gollop: Delacour and Scott's Waterfowl of the World (1954-59) has paintings of day-old ducklings. Jahn: Mrs. Colleen Nelson is also painting day-old ducklings for publication. In the 1950's F.A. Thompson, U.S.F.W.S., prepared a chart on the colours of soft parts of ducks for determining species and sex. U.S.F.W.S. at Jamestown and in Minnesota is working on coloured slide series. Hawkins: Michigan has data which indicate as much variation in plumage development within a brood as between plumage classes used for aging. Hammond: Can brood size and age data be collected in a manner that would make them useful in continental management?


Jahn: Luther Marsh in Ontario is one example of a highly productive once-drained waterfowl area. After drainage, Horicon Marsh, Wisconsin, did not produce vegetables only because technology had not advanced far enough, resulting in inadequate drainage. Now modern machinery has permitted yields of 125 bushels per acre on similar soils there. Productivity may fall off rapidly on such areas but it is economical to counter this by refertilizing. However, wind erosion is still a real problem on peat soils and because of the woody, unpacked material, subsidence of peat soils is another major problem. Crissey: Because of subsidence, water cannot be kept out of some peat areas in New York.

Wing survey

Hawkins: Sexing and aging of wings requires two types of individuals, one fairly well trained and the other an expert to check determinations. Crissey: U.S.F.W.S. has only two people, Sam Carney and Glen Smart, fully qualified. It will be a problem to send qualified instructors to Canada if there are too many wing-bees. The more common species are not too much of a problem but it is very difficult to become proficient with all species. Skill cannot be retained without doing. An adequate reference collection requires 25± wings of each age-sex group of each species (100 wings per species) to properly train people. Competency in this work is not related to proficiency in other fields. Jahn: Keys and slides should be studied in advance of training sessions.


Jahn: Who is going to follow through with research and other suggestions, tests, and analyses brought up at this seminar?
Previous Section -- Literature Cited
Return to Contents

Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo logo U.S. Department of the Interior | U.S. Geological Survey
Page Contact Information: Webmaster
Page Last Modified: Friday, 01-Feb-2013 19:13:29 EST
Sioux Falls, SD [sdww54]