Lewis M. Cowardin

Survival of wood duck and mallard broods in north-central Minnesota

Duckling survival in wood duck (Aix sponsa) and mallard (Anas platyrhynchos) broods was estimated from data obtained from 71 radio-marked brood hens on a study area in north-central Minnesota. Radio-marked hens produced 30 broods during the study, and 41 hens already leading broods were captured and radio-marked. Production estimates based on brood size counts were inflated by about 38 percent for wood ducks and 30 percent for mallards if total-brood losses were not taken into account. Mortality during the first 2 weeks of life was most severe, accounting for 86 percent of total recorded mortality in wood ducks and 70 percent in mallards. Rearing success was about 41 percent for wood ducks and 44 percent for mallards. Duckling survival was negatively correlated with distance of overland travel by young broods. Wood ducks had a shorter hen-brood bond than mallards, and presence of the hen appeared to affect duckling survival less in wood duck broods than in mallards.

US Fish and Wildlife Service 1979 wetland classification: A review*

In 1979 the US Fish and Wildlife Service published and adopted a classification of wetlands and deepwater habitats of the United States. The system was designed for use in a national inventory of wetlands. It was intended to be ecologically based, to furnish the mapping units needed for the inventory, and to provide national consistency in terminology and definition. We review the performance of the classification after 13 years of use. The definition of wetland is based on national lists of hydric soils and plants that occur in wetlands. Our experience suggests that wetland classifications must facilitate mapping and inventory because these data gathering functions are essential to management and preservation of the wetland resource, but the definitions and taxa must have ecological basis. The most serious problem faced in construction of the classification was lack of data for many of the diverse wetland types. Review of the performance of the classification suggests that, for the most part, it was successful in accomplishing its objectives, but that problem areas should be corrected and modification could strengthen its utility. The classification, at least in concept, could be applied outside the United States. Experience gained in use of the classification can furnish guidance as to pitfalls to be avoided in the wetland classification process.

A model of the productivity of the mallard duck

Abstract This paper describes a stochastic computer model that simulates recruitment of the mallard (Anas platyrhynchos) under different habitat conditions and management scenarios. The model incorporates several environmental phenomena and biological relations that affect mallard recruitment. Major events include arrival of mallards in the spring, daily survival of hens, initiation of nests, selection of nest sites, survival of nests until hatching, and survival of broods until fledging. The model was originally developed as a tool for synthesizing the results of research. Subsequently, we applied the model to a variety of management situations. We also describe the sources of estimates used in the model, evaluate its sensitivity to input parameters, and review some practical applications.

Wetland use, settling patterns, and recruitment in mallards

The correlation between number of May ponds in the Prairie Pothole Region (PPR) of North America and size of the continental mallard (Anas platyrhynchos) breeding population the following spring weakened from the 1950s to the 1980s, suggesting possible changes in suitability of prairie ponds for meeting reproductive needs. We studied wetland use and preferences of radioequipped female mallards by reproductive stage (1988-90) in eastern North Dakota and westcentral Minnesota and evaluated effect of land use on pair distribution in eastern North Dakota (1987-91). May pond density varied among years and study areas, with changes in number of temporary and seasonal ponds accounting for 93% of variation in total ponds. During all reproductive stages, semipermanent basins were used most by females, but temporary and seasonal ponds were preferred during prenesting and egg production. Accounting for number of relocations, number of ponds used varied by year, by reproductive stage and with pond density during egg production. Numbers of breeding mallard pairs in stratum 46 in eastern North Dakota increased as May ponds increased from 1963 to 1985, but 33,659 fewer breeding pairs on average were present in 1971-85 than in 1963-70. Number of breeding pairs declined relative to May ponds from the 1960s to the 1980s, probably because fewer pairs settle in temporary and seasonal ponds as the percent of landscape in cropland increases. Waterfowl managers in the PPR should target efforts to increase duck production on landscapes where non-cropped temporarily and seasonally flooded wetland habitats are plentiful, thereby increasing cost effectiveness of management actions taken to increase nest success rate.

HABITAT USE AND HOME RANGE OF MALLARDS BREEDING IN MINNESOTA

Telemetry techniques were used to study habitat use and home range of 12 drake and 12 hen mallards (Anas platyrhynchos) in the forested region of north-central Minnesota during the 1968 to 72 breeding seasons. Circumneutral bogs and seasonal wetlands were the most frequently used communities; the lakeshore communities most used were sand-gravel, overhanging brush, and bog mat. Based on the availability of habitat, the highest preference shown was for the seasonal community and the least for the softwood swamp; however, all communities were used to some extent during the breeding season. Lakeshore was always among the habitats most frequently used by pairs. Twelve nests were found, nine in nonpermanent wetlands and three in upland forest sites. Mean home range was 210 ha for hens and 240 ha for drakes. The long axis of the home ranges of drakes and hens averaged 2.8 and 2.7 km, respectively. Hens had smaller home ranges during the laying period (anti x = 70 ha) than during prenesting (anti x = 135 ha).

Remote sensing for identification and classification of wetland vegetation

Multispectral photography and ground truth were obtained on an area 12 miles (19.3 km) east of Bemidji, Minnesota, to identify and map wetlands less than 2 acres (0.8 hectare) in size, to map emergent vegetation in lakes, and to explore the feasibility of classifying vegetation from aerial photographs. Wetlands less than 2 acres in size were identified on photography taken in May 1971, and emergent vegetation was recorded on purposely overexposed infrared black and white photography from a flight in September 1971. Several vegetation types and species groups were recognizable with the aid of color, color infrared, and black and white infrared photography. Proper timing of flights, use of multispectral photography, and knowledge of the ecology of the area are considered essential for wetland mapping by remote sensing. J. WILDL. MANAGE. 38(2):308-314 Investigations of the ecology of birds and other wildlife usually require data on the area of and types of habitat available to the animals. Measurements of habitat made from ground surveys are often time-consuming and, therefore, must be restricted to relatively small areas. Remote sensing is a relatively new tool, which, when used in conjunction with ground surveys, enables the ecologist to rapidly survey large areas of land and water, and discover details that are not readily apparent from ground surveys (Colwell 1967). For years, foresters have made extensive use of remote sensing for timber management and inventory (Avery 1968), but work on aquatic habitats has been more restricted. Studies by Kelly and Conrod (1969), Lukens (1968), Cameron (1950), Zohari et al. (1955), Mathisen (1966), Olson (1964), Nelson et al. (1970), and Work and Gilmer (1973) have demonstrated that remote sensing has great promise for wetland mapping and inventory. Recently many investigators have had considerable success in recognizing wetland plant communities and even plant species with the aid of color and color infrared films (Anderson 1968, Anderson 1969, Thompson 1972, Russell and Wobber 1972, Reimold et al. 1973, Seher and Tueller 1973). We required detailed habitat maps for a long-term investigation of waterfowl ecology in Minnesota (Gilmer et al. 1973). Preliminary maps were prepared from ground surveys and from 1:15,840 infrared summer photography obtained from the U.S. Forest Service, but difficulty was experienced in distinguishing small wetlands under the canopy of a hardwood forest. Vegetation in lakes was difficult to map either from a boat or with the aid of aerial photographs. This report considers the use of multispectral photography: (1) to find and map wetlands less than 2 acres in size (minimum size mapped by Mathisen [1966]) under a forest canopy, (2) to accurately map stands of emergent vegetation in lakes, and (3) to explore the feasibility of using multispectral photography to classify wetlands.

Natural cavities used by wood ducks in north-central Minnesota

Radio telemetry was used to locate 31 wood duck (Aix sponsa) nest cavity sites in 16 forest stands. Stands were of 2 types: (1) mature (t = 107 years) northern hardwoods (10 nest sites), and (2) mature (i = 68 years) quaking aspen (Populus tremuloides) (21 nest sites). Aspen was the most important cavity-producing tree used by wood ducks and accounted for 57 percent of 28 cavities inspected. In stands used by wood ducks, the average density of suitable cavities was about 4 per hectare. Trees containing nests were closer to water areas (P < 0.05) and the nearest forest canopy openings (P < 0.01) than was a random sample of trees from the same stands. A significant (P < 0.005) relationship existed between the orientation of the cavity entrance and the nearest canopy opening. Potential wood duck cavities usually were clustered within a stand rather than randomly distributed. Selection of trees by woodpeckers for nest hole construction probably influenced the availability of cavities used by wood ducks. A plan for managing forests to benefit wood ducks and other wildlife dependent on old-growth timber is discussed. J. WILDL. MANAGE. 42(2):288-298 McCabe (1966) and Aultfather (1966) pointed out the lack of information needed to guide foresters in multiple-use programs beneficial to wood ducks. There is little information on the use of natural cavities by wood ducks, particularly in the northern forested regions of the Lake States. Increases in wood duck populations in certain areas have been attributed to nest boxes (Bellrose et al. 1964, Grice and Rogers 1965), but, in some forested areas, large scale nest box programs may not be practical. Furthermore, timber resources that can provide a sustained source of cavity sites may be available. The primary objectives of this paper are to describe: (1) the home range of wood duck hens in relation to the nest site, (2) features of the habitat used by the nesting pair and characteristics of the forest stands containing cavity trees, (3) characteristics of the cavity tree and its immediate surroundings, and (4) guidelines for foresters managing northern forests to consider in formulating multiple use programs that would benefit wood ducks and other cavity-dwelling wildlife species. We thank H. A. Doty for critically reviewing the manuscript and W. A. Aultfather and G. W. Gullion for providing suggestions in manuscript preparation. E. Johnson provided assistance in photo interpretation and in the description of forest site conditions. T. S. Klodfelter and R. S. Stott assisted with data collection. We were assisted in statistical analyses by D. H. Johnson and in computer processing by D. A. Davenport. Telemetry equipment was constructed and maintained by the engineering staff, Cedar Creek Bioelectronics Lab, University of Minnesota. 1This research was supported by the U.S. Fish and Wildlife Service, University of Minnesota, National Institute of Health Training Grant TO1-GM01779, and the U.S. Energy Research and Development Administration (C00-1332-126). 2 Present address: U.S. Fish and Wildlife Service, Northern Prairie Wildlife Research Center, Jamestown, North Dakota 58401. 3 Present address: Department of Zoology, Washington State University, Pullman 99163. 4 Present address: R.R. #1, Valmeyer, Illinois 62295. 288 J. Wildl. Manage. 42(2):1978 This content downloaded from 157.55.39.104 on Sat, 18 Jun 2016 06:48:44 UTC All use subject to http://about.jstor.org/terms WOOD DUCK USE OF NATURAL CAVITIES .Gilmer et al. 289

Wildlife Habitat Management on the Northern Prairie Landscape

The northern prairie landscape has changed dramatically within the past century as a result of settlement by Europeans. Natural ecosystems have been disrupted and wildlife populations greatly altered. Natural resource agencies control only limited areas within the landscape, which they cannot manage independently of privately owned lands. Wildlife managers need first to set quantifiable objectives, based on the survival, reproduction, and distribution of wildlife. Second, they need to build public support and partnerships for meeting those objectives. Finally, they need to evaluate progress not only with respect to attitudes of the public and partners but, more importantly, of the wildlife response. This paper describes some useful tools for managing information at all phases of this process. We follow by discussing management options at a landscape level. Examples are given that involve agency lands as well as private lands, managed for biological resources and diversity as well as economic sustainability.

Use of flooded timber by waterfowl at the Montezuma National Wildlife Refuge

Waterfowl use of bottomland hardwood timber stands which were flooded and killed was studied at the Montezuma National Wildlife Refuge, Seneca Falls, New York, from 1962 to 1964. Comparisons of use were made among six habitat types containing dead timber, stumps, and no timber, and with and without emergent vegetation. An index to waterfowl use was derived by direct counts and by counts made with automatic cameras which photographed randomly selected plots in each habitat type. Movement between types was studied by observation of both marked and unmarked birds. The camera index of use showed that cut timber with emergent vegetation received the greatest overall use. Use was positively correlated with the proximity of the plot to emergent vegetation and nearest vegetative type boundary. A stand flooded for 7 years was used primarily by black ducks ( Anas rubripes) and mallardls ( A. platyrhynchos) . Use of stands flooded for 20 years was dominated by American widgeon (Mareca americana). Waterfowl spent more time resting than feeding in timbSered areas, and more time feeding than resting in marsh areas. Young-of-the-year did not move between pools after they had reached an age of IIc ( Gollop and Marshall 1954 ). Use by broods was greatest in areas near emergent vegetation. Flying birds used timbered areals during the daytime and non-timbered areas at night during fall. Flooded dead timber appeared to be attractive to waterfowl because it furnished abundant loafing sites. The management of green tree reservoirs for production of both waterfowl and wood has become a recognized practice in the south (Rudolph and Hunter 1964) but little is known about the value of dead timber impoundments in the north. The Montezuma National Wildlife Refuge contains several large tracts of bottomland timber which were flooded in the past as well as large areas of cattail ( Typha sp. ) marsh which are without timber. The presence of these areas furnished an opportunity to study a type of waterfowl habitat about which little was known. This paper describes the use of the flooded-timber habitats by waterfowl and compares it with that of cattail marsh habitats. An earlier paper ( Cowardin et al. 1967 ) described waterfowl production on the same areas. Uhler ( Personal communication ) studied 1This study was supported by the New York Cooperative Wildlife Research Unit and the Division of Wildlife Refuges of the Bureau of Sport Fisheries and Wildlife. 2 Present address: Northern Prairie Wildlife Research Center, Bureau of Sport Fisheries and Wildlife, Jamestown, North Dakota. waterfowl use and production on a number of small impoundments containing dead timber at the Patuxent Wildlife Research Center near Laurel, Maryland. He found that impoundments with dead timber soon became choked with bladderwort ( Utricularia sp.) and that value to waterfowl was limited. When dead timber was removed from the impoundments following drawdown, Uhler noted an increase in valuable waterfowl food plants and in waterfowl use. DiAngello ( 1953 ) studied plant succession, and waterfowl use and production on several flooded forest impoundments of varying age in Michigan. He found that the impoundments were of considerable value to waterfowl but that their value diminished with time. He attributed the loss in value to a decrease in the amount of duckweed (Lemna spp.) which was present in the first few years after flooding. Moore (1959) studied the vegetation and waterfowl use of a number of flooded swamps in eastern Massachusetts. He found that wood ducks (Aix sponsa) and black ducks made extensive use of wooded impoundments during fall mi-

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.