Jerome R. Serie

Advantages in Mathematically Weighting Waterfowl Food Habits Data

The relative importance of various foods occurring in the diet of blue-winged teal (Anas discors), pintail (A. acuta), and gadwall (A. strepera) breeding in south-central North Dakota and lesser scaup (Aythya affinis) breeding in the vicinity of Great Slave Lake, Northwest Territories, are compared by the aggregate volume and aggregate percent methods. Advantages of the aggregate percent method are discussed in relation to the information presented. J. WILDL. MANAGE. 38(2):302-307 Recent investigations of the foods consumed by breeding and immature ducks inhabiting prairie and subarctic wetlands of North America have emphasized the value of using the esophageal contents rather than the gizzard for this purpose (Perret 1962; Bartonek and Hickey 1969a, 1969b; Dirschl 1969; Sugden 1969; Bartonek and Murdy 1970; Swanson and Bartonek 1970; Swanson and Nelson 1970; Krapu 1972; Swanson and Sargeant 1972). This change was implemented primarily through improved sampling procedures which provided birds containing substantial amounts of food in their esophagi. The trend toward utilizing the esophagus of waterfowl somewhat paralleled an earlier and similar change that occurred in food habit studies of upland game birds (Martin et al. 1946; Martin et al. 1951). The purpose of this paper is to reevaluate two existing methods of presenting either volumetric or weight data in light of the current use of the esophagus as a source of information. The data that form the basis for these comparisons were gathered to support feeding ecology studies of blue-winged teals, pintails, and gadwalls in south-central North Dakota and lesser scaups in the Northwest Territories. Appreciation is extended to P. F. Springer for critically reviewing the manuscript.

Feeding Ecology of Breeding Blue-Winged Teals

A 5-year investigation of factors influencing the selection of foods consumed by blue-winged teals (Anas discors) during the breeding season in the glaciated prairie region of south-central North Dakota showed that birds first arriving on the breeding grounds consumed a diet consisting of 45 percent invertebrates. The proportion of animal foods in the diet increased to 95 percent at the onset of the nesting season. The quality and quantity of foods selected at any given time were influenced by the biological demands and morphological adaptations of the bird, the behavior and ecology of the invertebrates selected as foods, and the general nature of the aquatic ecosystems as determined by the hydrology and geology of the area and modified by land use and weather. Feeding activities changed significantly when food availability within the aquatic ecosystem changed. During the spring and early summer, temporary and seasonal wetlands, if not severely disturbed, were of paramount importance to breeding blue-winged teals since they provided abundant and readily available, high protein, animal foods. Later in the summer when seasonal wetlands began to dry up, insects began to emerge in the semipermanent ponds and lakes, and feeding intensity shifted to these more permanent waters. This trend, however, was often reversed temporarily during the early summer following heavy precipitation that refilled shallow water areas and again stimulated invertebrate development. J. WILDL. MANAGE. 38(3):396-407 Information concerning foods consumed by blue-winged teals during the breeding season is scarce. Early studies concentrated primarily on fall and winter collections (Mabbott 1920, Bennett 1938, Martin and Uhler 1939, Kortright 1943). The data presented here describe the foods selected by breeding blue-winged teals over a 5year period (1967-71) and are part of a larger study designed to provide information to assess the significance of changes occurring in waterfowl breeding habitat on the prairies. The blue-winged teal is the most abundant breeding duck in North Dakota; the statewide population in 1967 was estimated to contain 680,000 breeding pairs (Stewart and Kantrud 1972a). The various aspects of the life history of the blue-winged teal have been described by Bent (1923), Bennett (1938), Kortright (1943), Delacour (1956), and Johnsgard (1965). The first birds generally arrive in south-central North Dakota during April and nesting is usually initiated by mid-May. Attempts by unsuccessful females to renest are generally terminated in early July. Appreciation is extended to J. C. Bartonek for encouragement and sincere interest; and to V. A. Adomaitis and J. A. Shoesmith for chemical analysis; D. H. Johnson and D. A. Davenport for aid in statistical analysis; and V. A. Adomaitis, H. F. Duebbert, F. B. Lee, R. E. Stewart, and P. F. Springer for critically reviewing the manuscript.

Limnological conditions influencing duckling use of saline lakes in south-central North Dakota

The distribution of ducklings on North Dakota saline lakes and their tolerance of these waters under controlled conditions were investigated. Sulfates dominated the anions and sodium, magnesium, and potassium the cations of the lakes investigated. Salt concentrations are altered by changes in water volume and construction-induced hydrologic barriers that change the natural water flow and mixing. Hydrologic characteristics of saline lakes dictate the limnological conditions that influence duckling use by controlling salt concentrations, the availability of fresh water, and aquatic foods. Ducklings were closely associated with fresh inflow from spring seepages or adjacent wetlands of low salt content. Ducklings that used sheltered bays with chemically stratified water were able to feed on fresh water. Ducklings <1-3 days of age experienced some mortality at 16 mmhos/cm and could not tolerate salt concentrations in prairie lakes that exceeded 20 mmhos/cm unless fresh water was also available. Salt concentrations of 17 mmhos/cm significantly reduced growth. High levels of magnesium and sulfates may cause greater stress on birds than equivalent concentrations of sodium chloride that are processed by the supraorbital salt glands. J. WILDL. MANAGE. 48(2):340-349 The prairie pothole region of North America contains a high density of shallow wetland basins that were formed by glaciation and developed under the influence of a semiarid climate. The hydrologic regimes of these basins dictate their chemical characteristics and subsequently the plant and invertebrate communities they support (Stewart and Kantrud 1971, Swanson et al. 1974). Lakes in south-central North Dakota that contain elevated salt levels function as hydrologic sumps, occur in low-lying basins, and are usually associated with glacial outwash or meltwater channels. The prairie pothole region supports a major segment of the annual continental waterfowl population, however, little is known of the response of breeding ducks to its saline lakes (Serie and Swanson 1976). Waterfowl are attracted to saline lakes where they feed on a variety of salt-tolerant invertebrates, vascular plants, and filamentous algae (Swanson et al. 1974, Serie and Swanson 1976, Krapu and Swanson 1978). Although adults are known to fly between freshwater sites and saline lakes where they feed, little information exists on the suitability of this type of habitat for ducklings. Female dabbling ducks nest on islands in permanent saline lakes (Duebbert et al. 1983) but the fate of the broods that they produce has not been determined. Current interest in the use of wastewater derived from irrigation return flows and geothermal effluent to develop waterfowl habitat requires more knowledge about waterfowl response to saline waters. Land-use practices can also increase salt levels of natural wetlands by initiating hydrologic changes. The objective of this study was to identify the limnological conditions that influence duck brood use of saline lakes. This paper details: (1) a description of the chemical characteristics of saline lakes in south-central North Dakota; (2) a survey 340 J. Wildl. Manage. 48(2):1984 This content downloaded from 157.55.39.132 on Thu, 15 Sep 2016 06:06:12 UTC All use subject to http://about.jstor.org/terms DUCKLING DISTRIBUTION * Swanson et al. 341 of their use by duck broods; and (3) exposure of incubator-hatched ducklings to their waters. Appreciation is extended to M. G. Barron, P. F. Springer, and J. F. Wolf for assistance in the field; D. H. Johnson for aid in statistical analysis; and H. F. Duebbert, A. B. Sargeant, and T. C. Winter for reviewing the manuscript.

Effect of restrictive harvest regulations on survival and recovery rates of American black ducks

Population management of waterfowl requires an understanding of the effects of changes in hunting regulations on harvest and survival rates. Mean survival and recovery rates of American black ducks (Anas rubripes) were estimated during 3 periods of increasingly restrictive harvest regulations: 1950-66, 1967-82, and 1983-93. From the first to the second period, direct recovery rates declined for at least 1 age class in 4 of 6 reference areas, with a mean decline of 14% for adult and 7% for immature black ducks. From the second to the third period, direct recovery rates declined in all areas, declines averaging 37% for adults and 27% for immatures. Estimated mean survival rates increased from the first to the second period, consistent with a model of additivity of hunting mortality. Limited evidence existed for increases in survival rates from the second to the third period for immature males. For adults, however, survival increased less between these periods than would be expected if hunting mortality were additive and changes in recovery rates were proportional to changes in hunting mortality, Changes in survival and recovery rates of black ducks banded postseason were similar to those of adults banded preseason. Comparisons among estimates by degree blocks of latitude and longitude indicate that, at least between 1967 and 1983, estimated survival rates of immature and adult black ducks were lower in areas with high direct recovery rates. Smaller samples of banded birds and changes in banding locations in recent vears may be limiting ability to evaluate consequences of recent changes in harvest rates. These correlation-based studies are limited in their ability to explain causes of observed changes in survival rates, suggesting the need for alternative approaches such as adaptive harvest management to increase understanding of the effects of hunting on black duck populations.

Influence of age and selected environmental factors on reproductive performance of canvasbacks

Age, productivity, and other factors affecting breeding performance of canvasbacks (Aythya valisineria) are poorly understood. Consequently, we tested whether reproductive performance of female canvasbacks varied with age and selected environmental factors in southwestern Manitoba from 1974 to 1980. Neither clutch size, nest parasitism, nest success, nor the number of ducklings/brood varied with age. Return rates, nest initiation dates, renesting, and hen success were age-related. Return rates averaged 21% for second-year (SY) and 69% for after-second-year (ASY) females (58% for third-year and 79% for after-third-year females)

Migration and winter distributions of canvasbacks staging on the Upper Mississippi River

Fall and winter distribution patterns of canvasbacks (Aythya valisineria) staging on the upper Mississippi River near LaCrosse, Wisconsin (navigational Pools 7 and 8) and Keokuk, Iowa (Pool 19) were studied during 1973-77. Sightings and recoveries obtained from 1,488 color-marked males during 1973-75 and 3,789 banded males and females during 1973-77 suggested 2 principal migration corridors: 1 extending eastward from Pools 7 and 8 to the eastern Great Lakes and southeast to the Mid-Atlantic Region and another southward from Pools 7 and 8 to the lower Mississippi Valley, Gulf Coast, and east Texas regions. These discrete populations stage concurrently on Pools 7 and 8 during the fall, but winter in different areas of the Atlantic, Mississippi, and Central flyways. Populations staging on Pool 19 were not discrete from those staging on Pools 7 and 8. A continual turnover of birds passing through these staging areas was indicated. Canvasbacks wintering in the Mississippi and Central flyways were widely dispersed among a variety of habitats, whereas canvasbacks wintering in the Atlantic Flyway were concentrated in a few traditional habitats. Canvasbacks exhibited strong fidelity to wintering areas. Distribution patterns and population attributes of canvasbacks during fall and winter may be explained by the predictability of natural foods and their ability to exploit these foods. J. WILDL. MANAGE. 47(3):741-753 Principal migration corridors of canvasbacks have been described by Stewart et al. (1958), Geis (1959), and Bellrose (1968). The eastern continental population of canvasbacks was reported staging during fall on Lake Christina and Heron Lake in Minnesota (Smith 1946); Lakes Poygan, Koshkonong, Butte des Morts, Winnebago, and Winneconne in Wisconsin (Jahn and Hunt 1964); the Detroit River, Lake St. Clair, and Saginaw Bay in Michigan (Martz et al. 1976); and the Illinois River in Illinois (Mills et al. 1966). Canvasback use of these traditional staging areas declined dramatically from 1955 to 1966, during which time use of the upper Mississippi River, particularly navigational Pools 7, 8, and 19, increased (Mills et al. 1966; J. H. Stoudt, unpubl. rep., North. Prairie Wildl. Res. Cent., Jamestown, N.D., 1970; W. E. Green, unpubl. rep., Upper Miss. Fish and Wildl. Refuge, Winona, Minn., 1974). The effects of siltation, pollution, eutrophication, and rough fish on such preferred foods as fennelleaf pondweed (Potamogeton pectinatus), American wildcelery (Vallisneria americana), and fingernail clams (Sphaeriidae) have been cited (Mills et al. 1966, Trauger and Serie 1974) as causal factors responsible for the disappearance of canvasbacks from formerly important staging

Age-class determination of canvasbacks

A technique was developed to distinguish yearling from adult canvasbacks (Aythya valisineria) in the field during spring on the basis of white flecking on the distal ends of selected wing feathers. Covert feathers from adults had well-defined vermiculation patterns whereas feathers from yearlings lacked such markings. These age-related characters were confirmed by paired comparisons of feathers from the same captive birds in consecutive years and by discriminant analysis of feathers using densitometric measurements from known-age wild birds. Reflective densitometric measurements of greater secondary coverts for females and males were significantly different between 1and 2-year-old and between 2and 3-yearold canvasbacks. Greater secondary coverts were the best feathers for recognizing age-classes of males and females. Densitometric values indicate low variability among different observers and within samples. J. WILDL. MANAGE. 46(4):894-904 The ability to recognize age-classes within a population is important in understanding aspects of reproductive biology and population dynamics (Trauger 1971, Johnson 1978, Krapu and Doty 1979, Raveling 1981). Due to the low population status of the canvasback in recent years, the influence of breeding age on individual productivity has been of concern (Olson 1964, Trauger 1974b, Bellrose 1976). A reliable technique for distinguishing between age-classes of canvasbacks in spring was needed to identify the influence of age on reproductive success of yearlings and older, experienced birds. Techniques for separating age-classes, recently developed for other species of waterfowl, use several variables which complicate their application and reliability (Dane 1968, Dane and Johnson 1975, Blohm 1977, Krapu et al. 1979, Wishart 1981). Based on feather dimensions or distinctive markings, these techniques use key wing feathers or a combination of feathers to establish criteria for separating age-classes. White flecking or vermiculation patterns on the wing coverts of canvasbacks were recognized by Carney (1964) as a valuable criterion for separation of ageclasses. He developed a technique, primarily for use during the fall, which depended largely upon shape, wear, and degree of white flecking on the tertial feathers. This technique is less effective during the breeding season because of feather wear and replacement. The objectives of our study were to (1) identify wing feathers which reliably distinguish yearlings from older canvasbacks in the field at any time of year, and (2) develop a technique for quantitatively measuring these age-related characters. We acknowledge the Data Production Division of the EROS Data Center, U.S. Geological Survey, Sioux Falls, S.D., and in particular J. McCord and C. Lawson for assistance in development of densitometry for feather age classification techniques; E. L. Ferguson for encouragement; M. I. Meyer for preparing drawings of feathers; F. B. Lee for supervising the rearing of known-age canvasbacks; D. H. Johnson for assistance 1 Present address: Division of Wildlife Ecology Research, U.S. Fish and Wildlife Service, Washington, DC 20240. 2 Present address: U.S. Fish and Wildlife Service, Box 26A, Route 1, Fergus Falls, MN 56537. 894 J. Wildl. Manage. 46(4):1982 This content downloaded from 157.55.39.27 on Wed, 07 Sep 2016 06:34:55 UTC All use subject to http://about.jstor.org/terms AGE-CLASSES OF CANVASBACKS * Serie et al. 895 with statistical analysis of data; and H. F. Duebbert and D. H. Johnson for editorial review of the manuscript.

Body weight and composition dynamics of fall migrating canvasbacks

We studied body weights and composition of canvasbacks (Aythya valisineria) during fall migration 1975-77 on stopover sites along the upper Mississippi River near La Crosse, Wisconsin (Navigational Pools 7 and 8) and Keokuk, Iowa (Navigational Pool 19). Body weights varied (P < 0.001) by age and sex without interaction. Weights varied by year (P < 0.001) on Pools 7 and 8. Mean weights increased (P < 0.01) within age and sex classes by date and averaged 3.6 and 2.7 g daily on Pools 7 and 8 and Pool 19, respectively. Percent fat was highly correlated (P < 0.001) with carcass weight for each age and sex. Live weight was a good predictor of total body fat. Mean estimated total body fat ranged from 200 to 300 g and comprised 15-20% of live weights among age and sex classes. Temporal weight patterns were less variable for adults than immatures, but generally increased during migration. Length of stopover varied inversely with fat reserves among color-marked adult males. Variation in fat condition of canvasbacks during fall may explain the mechanism regulating population ingress and egress on stopover sites. Fat reserves attained by canvasbacks during fall stopover may have adaptive significance in improving survival by conditioning for

Use of social indices to predict reproductive success in canvasbacks

We correlated temporal changes in social groupings of canvasbacks (Aythya valisineria) breeding near Minnedosa, Manitoba, with an independent estimate of hen success during 1974-80. Roadside counts of pairs, lone males, and flocked males were made along transects at 5-day intervals, normalized to percentages to allow comparisons among years, and plotted to obtain measurements of selected areas between and under the curves. An estimate of hen success was regressed on these selected graph areas each year to derive a predictive equation. Graph areas (social indices) determined from temporal changes in the proportion of pairs, lone males, and flocked males correlated (r2 = 0.69-0.93) with hen success. This technique avoids the need for pair counts, nest searches, and brood counts and provides managers with a useful index to evaluate local management practices and to predict yearly production in time for setting hunting regulations. J. WILDL. MANAGE. 54(1):66-72 With onset of egg laying and incubation, female ducks become less visible, and observed social groups change from predominantly paired males and females to mostly lone and flocked males (Dzubin 1969). LeBret (1961) found that hatching dates of mallards (Anas platyrhynchos) could be calculated from the time pairs began to break up and lone males first began to appear. Dzubin (1969) found that when lone male mallards first comprised over 10% of pairs, females were beginning egg laying, and the first appearance of 2-3 males in a group indicated the start of incubation. Olson (1964) reported that canvasback sex ratios in early June provided a useful index to ensuing production. Therefore, if we assume observed males to be paired with nesting females and if there is minimal immigration or emigration in the local population, then seasonal changes in observed social structure of the population should be related to some measure of female reproductive success. Traditional methods of estimating reproductive success in ducks require detailed information on the size of the breeding population and the number of young produced for any given area. However, in addition to being time conI Present address: U.S. Fish and Wildlife Service, Office of Migratory Bird Management, Laurel, MD 20708. This content downloaded from 157.55.39.84 on Tue, 07 Jun 2016 05:24:06 UTC All use subject to http://about.jstor.org/terms J. Wildl. Manage. 54(1):1990 CANVASBACK BREEDING INDEX * Serie and Cowardin 67 suming and labor intensive, these methods must overcome a wide spectrum of potential biases, such as weather, breeding phenology, bird mobility, behavior, and changing observation rates based on vegetative growth (Diem and Lu 1960, Dzubin 1969, Sauder et al. 1971, Sorenson 1978, Sugden and Butler 1980). Alternative methods depend on use of radios (Cowardin et al. 1985) and marking techniques (Trauger 1971) to track individual females and assess reproductive success, but they are also subject to bias (e.g., radio malfunction, marker loss, and behavior modification). In spite of these special problems, accurate estimates of annual productivity are integral to the management of continental duck populations and are necessary to formulate harvest strategies. Therefore, development of new, more rapid, and reliable methods of indexing annual breeding success are needed for setting annual hunting regulations and assessing management practices on local areas. We described temporal changes in social groups of canvasbacks during the breeding period and investigated the potential for using social indices to predict reproductive success. This method of indexing productivity was first described by J. R. Serie (J. R. Serie, 15th Semin. Breeding Biol. of Waterfowl, Delta Waterfowl and Wetland Res. Stn., Manitoba, 1980) and was later adapted and modified by Hochbaum et al. (1987). J. H. Stoudt initially established roadside transects near Minnedosa, Manitoba, and we thank D. L. Trauger for his encouragement to periodically record canvasback social groups. Field assistance was provided by L. Deede, H. A. Doty, T. Fondell, T. Jessicoff, D. H. Johnson, J. H. Noyes, F. Roetker, and L. Vanderholf. We are grateful to M. G. Anderson and the Delta Waterfowl and Wetlands Research Station for their assistance. In particular, we are indebted to T. L. Shaffer for statistical analyses. We thank T. G. Hanson for typing the manuscript and J. E. Austin, G. S. Hochbaum, C. E. Korschgen, R. B. Oetting, A. B. Sargeant, and T. L. Shaffer for review of manuscript drafts.

Variation in body mass of wild canvasback and redhead ducklings

We assessed variation in body mass of ducklings in singleand mixed-species broods of wild Canvasbacks (Aythya valisineria) and Redheads (Aythya americana) 20-50 days old. Body mass of canvasback ducklings was not affected by year and season (early vs. late hatch date) despite changes in water conditions. Mean body mass of male and female Canvasbacks did not differ in Class IIA but did differ in older age classes. Within-brood differences in body mass tended to be higher in Class IIA ducklings (6-7% of mean body mass for Canvasbacks, 9-11% in Redheads) and generally declined to 4-6% in Class IIC and older ducklings. Some within-brood differences were as high as 20-30% of mean body mass. Tests to assess sources of within-brood variation (age, sex, and season) in body mass for Canvasbacks were inconclusive. Variation within broods was generally less than that among broods for both Canvasbacks and Redheads. The lack of differences in duckling body mass between singleand mixed-species broods for any age class, sex, or species suggests that mass was not affected by interspecific brood parasitism.