Harold H. Prince

Waterfowl Use of the Laurentian Great Lakes

Literature on habitat and limiting factors of waterfowl in Great Lakes wetlands and deep water habitats is reviewed; more than 30 species of waterfowl use coastal habitats at some time during the year. Waterfowl use of the Great Lakes has declined dramatically from presettlement times; the obvious cause is human encroachment on coastal wetlands and destruction of river delta and embayed wetland complexes. Loss of wetland habitats from diking and filling above the average water level constitutes a permanent habitat loss, especially during high water cycles. The greatest number of species and individuals use 15 concentration areas during the spring and fall migratory periods when use by diving ducks, sea and stiff tailed ducks, and swans and geese predominates. Lesser numbers of species use the coastal wetlands for breeding. Large concentrations of dabbling ducks, primarily mallards (Anas platyrhynchos) and American black ducks (A. rubripes), and mergansers (Mergus spp.) are found on ice-free areas during winter. Wetland habitats have become more favorable, due to human modifications, to dabbling duck species found in the prairie habitats of North America. Mallards have become the most numerous species breeding in coastal wetlands along with a concomitant decline in black ducks, which may be a consequence of introgression. Habitat modifications, degradation, and loss have great potential to affect existing waterfowl populations negatively and to point the way toward future research.

Laying Dates, Clutch Size and Egg Weight of Captive Mallards

This has led to several major reviews on the possible determinants of clutch size in birds (Cody 1971, Klomp 1970, von Haartman 1971). Waterfowl have posed particular problems because the chicks are precocial and do not require parental feeding, a factor that correlates with clutch size in many altricial species (Lack 1968a). Most hypotheses concerning the evolution of clutch size in waterfowl have implied that food supply for the female prior to laying and/or for the young is both a proximate and an ultimate determinant (Bengston 1971, Johnsgard 1973, Lack 1967, 1968a, 1968b, Ryder 1970). We report the results of an experiment in which single pairs of Mallards (Anas platyrhynchos) were held in identical breeding compartments and were thereby subjected to the same environmental cues for breeding. We determined laying dates, clutch sizes and egg weights for the same pairs of birds in 1973, 1974 and 1975. The responses of the birds in terms of the three parameters of nesting were considered to closely reflect interactions between genotype and environment. They should provide bases for evaluating proximate environmental effects in wild populations.

GEOGRAPHICAL GENETICS: CONCEPTUAL FOUNDATIONS AND EMPIRICAL APPLICATIONS OF SPATIAL GENETIC DATA IN WILDLIFE MANAGEMENT

Abstract Molecular-genetic technology and statistical methods based on principles of population genetics provide valuable information to wildlife managers. Genetic data analyzed in a hierarchical, spatial context among individuals and among populations at micro- and macro-geographic scales has been widely used to provide information on the degree of population structure and to estimate rates of dispersal. Our goals were to (1) provide an overview of spatial statistics commonly used in empirical population genetics, and (2) introduce analytical designs that can be employed to extend hypothesis-testing capabilities by incorporating space-time interactions and by using information on habitat quality, distribution, and degree of connectivity. We show that genetics data can be used to quantify the degree of habitat permeability to dispersal and to qualify the negative consequences of habitat loss. We highlight empirical examples that use information on spatial genetic structure in areas of harvest derivation for admixed migratory species, wildlife disease, and habitat equivalency analysis.

Dabbling duck-habitat associations during spring in Delta Marsh, Manitoba

We conducted helicopter surveys of dabbling ducks (Anatini) in randomly selected legal quarter sections (64.8 ha) in the Delta Marsh, Manitoba, between April and June 1976-78. Our objective was to census indicated pairs of five species (Anas acuta, A. clypeata, A. discors, A. platyrhynchos, A. strepera) to test for associations of species pair densities and species richness with floristic and physiognomic character- istics of surveyed areas. Water levels in Delta Marsh varied markedly among years with 1976, 1977, and 1978 representing high, low, and intermediate levels, respectively. Densities of most species increased dra- matically in 1977, a year of widespread drought. We suggest this resulted from influxes of dabblers displaced from drought-stricken habitats. Tests for dabbler-habitat correlations with stepwise multiple regression revealed several patterns. Pair densities of most species and species richness were positively correlated with the proportional cover of shallow marsh habitat within survey quarters in 1976, but negatively associated with the cover of forest in 1977. Only mallard, northern pintail, and species richness were positively asso- ciated with an index of emergent vegetation-water interspersion in all 3 years. We provide explanations for consistent habitat correlations and offer considerations for marsh management and future research.

Survival and Movements of Canvasback Ducklings

Because canvasback (Aythya valisineria) breeding areas have been reduced by wetland drainage and because density-dependent factors that limit survival of ducklings are poorly understood, we studied brood and duckling survival during 1983-90 and overland brood movements during 1988-89 on 2 study blocks (15.8 km 2 each) near Minnedosa, Manitoba. One block was designated as the experimental area where canvasback duckling production was experimentally enhanced, whereas the other block was an unmanipulated control. Individually marked female canvasbacks with ducklings were monitored to test the effects of canvasback brood density, presence of parasitic redhead (A. americana) ducklings, hatching date, and pond water levels on canvasback duckling survival. We observed no between-block differences in mean daily survival rates of canvasback ducklings during 1983-86. The experimental high-density area had higher (P < 0.05) duckling survival probabilities during 1987-88. Duckling survival was significantly related (P = 0.033) to duckling density but not (P = 0.56) June wetland water levels. Duckling survival probabilities were highly variable among years (range = 0.027 ± 0.007 [SE] to 0.623 ± 0.004 [SE]); survival rates in 1989-90 during severe drought were much lower than in previous years. We observed no consistent effect of hatching date on duckling survival among years. On the experimental study block in 1988, canvasback ducklings in broods containing parasitic redhead ducklings had lower (P = 0.013) survival during the first 7 days of life. Canvasback broods were observed on an average of 4 different ponds and traveled an average total overland distance of 1.5 km with no between-block differences. Density-dependent mortality of ducklings was not a factor in limiting recruitment of canvasbacks in the Minnedosa area.

Movements and Survival of Molt Migrant Canada Geese From Southern Michigan

Abstract We studied movements and survival of 250 female giant Canada geese (Branta canadensis maxima) marked during incubation with either satellite-monitored platform transmitting terminals or very high frequency radiotransmitters at 27 capture areas in southern Michigan, USA, in 2000–2003. We destroyed nests of 168 radiomarked females by removing eggs after day 14 of incubation, and we left nests of 82 incubating hens undisturbed after capture and marking. Of females whose nests we experimentally destroyed, 80% subsequently migrated from breeding areas to molt remiges in Canada. Among 82 nests left undisturbed, 37 failed due to natural causes and 51% of those females departed. Migration incidence of birds that nested in urban parks was low (23%) compared with migration incidence of birds that nested in other classes of land use (87%). Departure of females from their breeding areas began during the second and third weeks of May, and most females departed during the last week of May and first week of June. Based on apparent molting locations of 227 marked geese, birds either made long-distance migratory movements >900 km, between latitudes 51° and 64° N, or they remained on breeding areas. Molting locations for 132 migratory geese indicated 4 primary destinations in Canada: Western Ungava Peninsula and offshore islands, Cape Henrietta Maria, Northeast James Bay and offshore islands, and Belcher Islands, Hudson Bay, Canada. Following molt of remiges, Canada geese began to return to their former nesting areas from 20 August through 3 September, with 37% arriving on or before 15 September and 75% arriving on or before 1 October. Migration routes of geese returning to spring breeding areas were relatively indirect compared with direct routes taken to molting sites. Although overall survival from May through November was 0.81 (95% CI: 0.74–0.88), survival of migratory geese marked on breeding sites where birds could be hunted was low (0.60; 95% CI: 0.42–0.75) compared with high survival of birds that remained resident where hunting was restricted (0.93; 95% CI: 0.84–0.97). Nest destruction can induce molt migration, increase hunting mortality of geese returning from molting areas, and reduce human–goose conflicts, but managers also should consider potential impacts of increasing numbers of molt migrants on populations of subarctic nesting Canada geese.

The Social Organization of a Mallard Population in Northern Iowa

Twenty-two hen and 134 drake mallards were marked during a 2-year study of mallard (Anas platyrhynchos) breeding activity on Ventura Marsh in north-central Iowa. During April, sex ratios of mallards observed on breeding areas (54% drakes) were lower than those observed in fields or on open water areas (58% drakes). Numbers of mallards observed declined after the initial influx, and remained relatively constant throughout the breeding season. The number of breeding mallards appeared to be limited by pursuit flights. Sixty-four marked drakes, observed at least once with a hen spent an average of 17.6 days on the marsh whereas 70 drakes, not seen with hens averaged 1.3 days on the area. There was a continual turnover of lone drakes on the study area throughout the breeding season. The nests of 22 marked hens were destroyed between day 10 and 17 of incubation. Four of the hens left the study area, 3 remained but did not remate, and 15 remated. Of 11 identified rematings, 8 hens (73% ) returned to their original drake and 3 (27%) changed drakes after losing their nest. J. WILDL. MANAGE. 42(1):72-80 The social organization of mallard breeding populations is not clearly understood. Studies concerning courtship behavior, interaction between pairs, and nesting provide a base for understanding mallard mate selection and production. The pair is fundamental to mallard reproduction. Weidman and Darley (1971) reviewed the range of attitudes among investigators concerning the role of the mallard male and female in display and courtship. They concluded that the female is essential in directing display and that social display promotes pair formation, which occurs for the most part before spring migration (Hawkins in Hochbaum 1944:121; Weller 1965:227). Hochbaum (1944:16) and Sowls (1955:21) reflected the general acceptance by biologists that most mallards are paired upon arrival at spring breeding areas. Lebret (1961:105) defined a hen and drake as paired when they maintained close proximity when together and when the drake defended the female from other mallards. Pair interaction in the form of pursuit flights (3-bird flights) was described by Dzubin (1957), McKinney (1965) and Titman (1973). Pursuit and avoidance were believed responsible for the spacing of breeding pairs (Dzubin 1969a). The ultimate consequence of spacing appears to be a lessened competition for breeding requisites and dispersion of nests as an antipredator mechanism. Those pairs unable to enter a breeding system may attempt to est elsewhere, delay the breeding effort, or molt. During the reproductive effort, drakes were observed with hens on breeding areas throughout the laying period and for an average of 8 days into incubation (Lebret 1961:127). Dzubin (1955:286) reported drakes present in the vicinity of nests until day 14 of incubation. Unless the nest is destroyed or abandoned, the hen continues incubating until the eggs hatch. Nest destruction, which appears to be a limiting factor in the annual production of mallards, was reported by Dzubin and Gollop (1972) to 1 Support provided by Iowa Conservation Commission P-R Project W-115-R-2 and the Michigan Agricultural Experiment Station; Journal Article Number 7689. 2 Present address: Missouri Department of Conservation, Fish and Wildlife Research Center, Columbia 65201. 72 J. Wildl. Manage. 42(1):1978 This content downloaded from 157.55.39.215 on Tue, 30 Aug 2016 05:35:26 UTC All use subject to http://about.jstor.org/terms MALLARD SOCIAL ORGANIZATION * Humburg et al. 73 range from 22 to 73 percent, depending upon the area studied, nesting cover condition, predator density, water level, weather, and human disturbance. Renesting, as high as 77 percent (Keith 1961:67), plays an important role in maintaining annual production in breeding mallard populations. A pair bond is necessary for successful culmination of egg laying and clutch incubation (Dzubin 1970), so hens losing nests probably will not renest without remating, even though they can lay fertile eggs up to 17 days after insemination (Elder and Weller 1954:501). Renesting hens could select a drake from a variety of sources; the original mate, a drake originally paired with a different female, or a previously unpaired drake. Although few data are available concerning the breeding activity of unpaired drakes, Titman (1973:41) observed marked unpaired males for a short time in localized areas on a breeding marsh. He speculated that there may be a selective advantage for an unpaired drake to be available for breeding with renesting hens. Elder and Weller (1954) suggested that unpaired drakes are essential to high productivity by supplying mates to renesting hens. In studying pintails (Anas acuta) Smith (1968) found that pursuit flights may often result in rape of the female, insuring fertilization. However, unpaired drakes could be harmful to production by harrassing nesting hens (Titman and Lowther 1975). Investigations by Bellrose (1961) revealed mallard sex ratios generally favor drakes and ranged from 68 to 233 drakes: 100 hens, depending upon latitude, season, and data collection method. The percentage of drake mallards appears to have increased since 1970 (Bellrose 1976:230). Some biologists have advocated harvest of the excess drakes. Dzubin (1970) suggested that harvest of surplus drakes may be biologically justified if (1) no difference exists in the time required for sexual maturity in both sexes, (2) surplus drakes have no significance in providing mates for renesting hens, and (3) harvest of hens would not parallel drake harvest. With the advent of the point system in waterfowl hunting regulations, which allows for the harvest of surplus drakes, controversy has arisen concerning the biological implication that increased drake harvest could have on mallard production. This study was designed to describe the structure and relationships between various components of a mallard breeding population on a breeding area. Specifically, the breeding activity of drake and hen mallards relative to the nesting cycle of unsuccessful nesting hens is described. We gratefully acknowledge the assistance of V. Wright with the project design, E. Peloquin and B. Batt for assistance with methods and data analysis, and G. Dudderar and D. Beaver for evaluating the final manuscript. Field assistance was provided by T. Willson, A. Woodward, R. Andrews, and

IDENTIFICATION OF SOURCE POPULATION FOR GREENLAND CANADA GEESE: GENETIC ASSESSMENT OF A RECENT COLONIZATION

Abstract We used microsatellite markers, mitochondrial DNA (mtDNA), and satellite telemetry to infer the North American geographic origin and racial composition of Canada Geese (Branta canadensis) from newly colonized habitats in Greenland. Using likelihood-based assignment tests we determined that multilocus genotypes of Greenland Canada Geese were consistent with the hypothesis of origin from birds of the Atlantic Population breeding around southern Ungava Bay, Quebec, Canada. The Atlantic Population, based on previous studies of seasonal movements and demography, appeared to be reproductively isolated from the North Atlantic Population. We found that these two populations were genetically differentiated based on microsatellite allele and mtDNA haplotype frequencies. Findings of high levels of genetic discordance among North American breeding populations are consistent with migratory movements, despite high levels of distributional overlap of birds from the North Atlantic and Atlantic Populations during migration and on wintering areas. Findings based on genetic markers were concordant with satellite telemetry conducted during spring migration, which showed that birds destined for Greenland migrate through the southern Ungava Bay breeding colony. Genetic differences among these populations are useful for addressing other issues of ecological or management concern. Identificación de la Población Fuente de los Gansos Branta canadensis de Groenlandia: Evaluación Genética de una Colonización Reciente Resumen. Utilizamos marcadores microsatélites, ADN mitocondrial (ADNmt), y telemetría de satélite para inferir el origen geográfico en Norte América y la composición racial de los gansos Branta canadensis en hábitats recientemente colonizados en Groenlandia. Mediante pruebas de asignación basadas en verosimilitud, determinamos que los genotipos multilocus de los gansos de Groenlandia eran consistentes con la hipótesis de origen de aves de la población del Atlántico que se reproduce alrededor del sur de Ungava Bay, Quebec, Canadá. Con base en estudios previos de movimientos estacionales y demografía, la población del Atlántico pareció estar aislada reproductivamente de la población del Atlántico Norte. Encontramos que estas dos poblaciones son genéticamente diferentes en términos de frecuencias alélicas de microsatélites y haplotipos de ADNmt. El hallazgo de altos niveles de discordancia genética entre poblaciones reproductivas norteamericanas es consistente con los movimientos migratorios, a pesar de los altos niveles de superposición de las distribuciones de aves de las poblaciones del Atlántico y el Atlántico Norte durante la migración y en las áreas de invernada. Los resultados basados en los marcadores genéticos concordaron con la telemetría satelital llevada a cabo durante la migración de primavera, la cual mostró que las aves con destino a Groenlandia migran a través del sur de la colonia reproductiva de Ungava Bay. Las diferencias genéticas entre estas poblaciones son útiles para abordar otros asuntos de interés ecológico o de manejo.

Genetic methods for determining racial composition of Canada goose harvests

We used molecular genetic markers and established statistical methods to estimate proportional contributions of subspecies and breeding populations to admixed wintering and migratory Canada goose (Branta canadensis) harvests. We compared harvest estimates across spatially and temporally explicit sampling intervals. We characterized 997 individuals from breeding populations in Canada representing interior Canada geese (B. c. interior; n = 4) and in Michigan representing giant Canada geese (B. c. maxima; n = 5) for 5 microsatellite loci. We determined that microsatellite loci coupled with maximum-likelihood methods provided accurate and precise proportional contribution estimates of samples from each subspecies and population. We first conducted simulation analyses and derived harvest estimates for unknown individuals representing a range of plausible harvest mixture scenarios using blind tests. Based on harvested individuals collected over a 4-year period (1993-1996), we found that the racial composition of Canada goose harvests varied significantly among years and across early, regular, and late seasons within a year. Harvest composition varied spatially between management areas in different regions and between managed and private lands in close (<40 km) geographic proximity. Higher proportions of resident giant Canada geese were harvested during early hunting seasons and on private lands relative to migratory interior Canada geese. Harvest estimates suggest that individuals from different subspecies and populations are differentially abundant or susceptible to harvest at different times of the fall season, during different years, and populations across different geographic locations. Given that baseline genetics data are available for subspecies of management interest, genetic methods can provide harvest composition estimates at many spatial and temporal scales, including enumeration of statistical confidence.

AVIAN COMMUNITIES IN FORESTED RIPARIAN WETLANDS OF SOUTHERN MICHIGAN, USA

Descriptive studies are an important first step in developing assessment models for regional wetland subclasses. Objectives of this study were to gather benchmark information on the composition and structure of vegetation from minimally impacted riparian forested wetland sites in Michigan, USA, and to determine if species composition of the breeding bird community and relative densities of individual species varied among riparian and adjacent upland forest zones. Plant species richness, dominance, and structure differed greatly between floodplain wetlands and uplands and were similar among zones within floodplain forests. Of 54 breeding bird species recorded through point count surveys (1998–99), 39 were observed in both floodplain and upland forests, while 11 were found only in floodplains and 4 solely in the uplands. Detectable patterns of avian density across riparian and upland forest zones were evident for 31 breeding species. Most species preferred areas closest to the river over other zones, although a few species were more prevalent within interior floodplains or uplands as compared to riverside forests. Forested riparian wetlands in this region act as essential breeding habitats for many avian species not often found in upland areas and are especially important for obligate riparian species and rare or declining breeding birds observed within our sites. These results are consistent with many studies across North America, where riparian forests have been found to support disproportionately large numbers of breeding bird species as compared to more xeric forests and other upland habitats.