Northern Prairie Wildlife Research Center
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.
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?
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.
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.
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.
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.
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.
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.
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.