Atlantic Flyway Research Articles

Reproductive Success of Exotic Mute Swans in Connecticut

Mute Swans (Cygnus olor) are native to Eurasia and were introduced to North America, where free-ranging populations have existed since the early 1900s (Allin et al. 1987). Originally observed in New York, breeding populations of Mute Swans have expanded into all of the Atlantic coastal states from Maine to Maryland and also have become established in Michigan, Minnesota, Wisconsin, British Columbia, and Ontario (Willey and Halla 1972; Reese 1975, 1980; Allin et al. 1987; Knapton 1993). Allin et al. (1987) synthesized 33 years of population data on Mute Swans from the Atlantic Flyway and estimated a 1987 population of 5,300, with most of the birds in New York, Connecticut, Rhode Island, and New Jersey. In the southern New England states of Massachusetts, Rhode Island, and Connecticut, Mute Swans constitute a single population with considerable interchange of individuals among states (Willey and Halla 1972). During the 1960s and 1970s, the Chesapeake Bay population nested mostly on estuaries and tidal rivers (Reese 1975, 1980), as did the southern New England population (Willey and Halla 1972, Kania and Smith 1986). For instance, 90% of the Mute Swans in Rhode Island in 1967 nested on estuaries, and no nests were more than 5 km inland (Willey and Halla 1972). Since then, large numbers of Mute Swans in southern New England have started breeding at inland sites on lakes and ponds. Expanding Mute Swan populations may have detrimental effects on native biota. One concern is the influence of swan herbivory on aquatic vegetation (Willey and Halla 1972, Reese 1975, Allin et al. 1987, Conover and Kania 1994) and associated macro-invertebrates (Krull 1970); another is that Mute Swans are aggressive toward other waterfowl species (Willey and Halla 1972, Kania and Smith 1986, Allin et al. 1987, Conover and Kania 1994). Because many native species of waterfowl nest at inland sites, Mute Swans may pose more of a threat to native avifauna at inland sites than at estuaries and tidal rivers (Wil-

Long‐term changes in agricultural practices and wildfowling in an internationally important wetland, and their effects on the guild of wintering ducks

1. The Marais Poitevin, one of the principal wintering and passage sites for ducks and waders in the East Atlantic flyway, underwent agricultural intensification in the 1980s. The numbers of ducks declined in the period 1979–96 in the main roost, Baie de l’Aiguillon; this was a site‐specific phenomenon for which local factors were responsible. We describe here long‐term changes in some key characteristics of the wetlands, paying particular attention to the principal factors affecting the quality of waterbird habitat: the area of semi‐natural grasslands, water management and wildfowling. 2. The area of grasslands declined by 50% between 1970 and 1995, principally as a result of conversion to arable farmland. The pattern was observed over the whole area and was slightly more marked close to the day‐roost of the ducks. The rate of change was greatest in the 1980s. Water levels, and therefore the flooded area, were reduced over the study period during the months of May to November. The numbers of wildfowlers declined from the 1970s, but the number of artificial wildfowling ponds increased, especially after 1980. The number of birds killed did not decline and may have increased. The quality of the ducks’ habitat therefore declined by all three measures. 3. Four species, mallard, shoveler, teal and gadwall, showed an increase in other sites in north and west France either over the whole period or over the last part (1984–96), while declining (shoveler and mallard) or remaining stable in the Baie de l’Aiguillon. Pintail remained stable in the other sites, while showing a long‐term decline (over 30 years) in the Baie. Wigeon did not use the Baie in large numbers in the 1996 cold spell as they did until the 1980s. 4. The uncoupling of the trends for these species in the Baie from their trends in the other sites may reflect the loss of grassland feeding habitat in the Marais Poitevin. However, for mallard, pintail and shoveler the declines in the Baie were much stronger than the 50% loss of grasslands so other factors, such as the reduction in autumn flooding and/or shooting, are likely to have played a part. 5. Since the three measures of long‐term trends in duck habitat co‐varied it was not possible to separate their effects statistically. The hypotheses arising from this study need to be tested: this should be done using comparative and experimental approaches. Suggestions are made for the management of water levels and shooting in the feeding habitat close to the Baie de l’Aiguillon.

Birds, mussels, cockles and shellfish fishery in the Dutch Wadden Sea: How to deal with low food stocks for eiders and oystercatchers?

Intensive fishing in the Dutch Wadden Sea in the late 1980s and 1990, in combination with the effects of storms and ice and low spatfall, has led to an almost complete disappearance of intertidal mussel beds in 1990. Since then, this habitat type has re-established in only very few places, covering some hundreds hectares at the most. Lack of good spatfall in the late 1980s also resulted in low cockle stocks. These stocks were further reduced due to heavy mortality in the 1995/96 winter. These developments yielded very low food stocks for shellfish eating birds in some winters. This paper describes the fishery policy which came into force since 1993 and the effects the low food stocks have had on Eiders and Oystercatchers which are dependent on cockles and mussels. Eiders suffered higher mortality in 1991 and partly emigrated to alternative feeding areas on the North Sea and German Wadden Sea. Oystercatchers suffered higher mortality as well, were found in lower numbers in the Dutch Wadden Sea and in higher numbers in inland feeding areas. This information, together with a comparison of quantitative data on available food stocks and food consumption by birds, indicate that in some winters the number of shellfish eating birds has exceeded the carrying capacity of the Dutch Wadden Sea. Alternative food sources, such asMacoma balthica, Mya arenaria, Scrobicularia plana, Ensis americanus, Nereis spp. andArenicola marina cannot compensate for low mussel and cockle stocks. Before 1990, intertidal mussel beds must have acted as an important alternative food source. In the current situation, with hardly any intertidal mussel beds in the Dutch Wadden Sea, cockles represent the major food source, especially in winter. Since cockle stocks can be very low in some years they are an unreliable food source at the same time. Intertidal mussel beds represent a winter resistant and a more reliable food source. These considerations are important viewpoints in the discussion on a future fishery policy for the Dutch Wadden Sea. The most important conclusions from the present analysis is that re-establishment of intertidal mussel beds in the Dutch Wadden Sea is essential to allow the area to play its role as vitally important wetland in the East Atlantic flyway. In order to achieve this goal future fishery on intertidal mussel beds should be highly restricted.

A Survey for Mallard Pairs in the Atlantic Flyway

During 1989-92, spring surveys of randomly selected, 1-km2 plots, stratified by physiographic strata, were conducted in the Atlantic Flyway from New Hampshire to Virginia, to estimate mallard (Anas platy- rhynchos) pairs. All potential waterfowl habitat in each plot was checked by ground crews. The adjusted mean mallard pair estimate over the 4-year period was 300,849 (range 271,193-320,642, mean SE 22,455) for the region surveyed. Ground plot checks are a practical way to survey mallard pairs in the upper Atlantic Flyway. J. WILDL. MANAGE. 61(4):1191-1198

Haemoproteus greineri in wood ducks from the Atlantic flyway.

Thin smears of blood were examined from 157 wood ducks (Aix sponsa) trapped at Savannah National Wildlife Refuge (South Carolina, USA) and Harris Neck National Wildlife Refuge (Georgia, USA) during spring and summer, 1994 and 1995. Thirteen wood ducks (8%) were infected with blood parasites. Eleven of these birds were infected with Haemoproteus nettionis, seven with Leucocytozoon simondi, and five with unidentified microfilariae. Additionally, eight wood ducks (5%) were infected with Haemoproteus greineri. This is the first record of H. greineri in anatids trapped along the Atlantic Flyway south of Labrador and the first record of this species in wood ducks. To further characterize the distribution of H. greineri in the wood duck, blood smears were examined from hatching year ducks trapped at 10 different Atlantic flyway locations during spring and summer, 1980 to 1983. Haemoproteus greineri was found in wood ducks trapped in all 10 locations which extend from 46 degrees N latitude in New Brunswick to 37 degrees N latitude in Virginia. These findings indicate that H. greineri is not exclusively boreal in distribution, but also is found, at least in wood ducks, along much of the Atlantic Flyway.

Population Dynamics of White-Winged Scoters

A significant (P < 0.01) decline between 1961 and 1993 in ratio of harvested young per adult in the Atlantic Flyway (age ratio) of white-winged scoters (Melanitta fusca) led us to examine annual survival rates and harvest of this species. Compared to waterfowl with similar life histories, black scoters (M. nigra) and surf scoters (M. perspicillata), the decline in age ratios of white-winged scoter age ratios was not significantly different (P = 0.11). Adult females banded at Redberry Lake, Saskatchewan that winter along both coasts, had high annual survival rates (0.773 ? 0.0176 [SE]). High harvest in the Atlantic Flyway was not followed by an increase in production (age ratios) the following year or 2, i.e., there was no short-term rebound in recruitment by the population. Harvest of white-winged scoters in the Atlantic Flyway was explained by the age ratio in the fall flight and by hunter effort. J. WILDL. MANAGE. 61(1):222-227

Population study and management of Atlantic Flyway Canada geese

Numbers of wintering Canada geese ( Branta canadensis ) in different regions of the Atlantic Flyway have significantly changed since the 1950s. During the 1980s, numbers increased in the mid-Atlantic and declined in the Chesapeake regions. A neckband study during the 1980s tested hypotheses that differential survival or movement caused changes in wintering numbers. The earlier studies and a reanalysis of the movement data using MSSURVIV indicated that the changes in wintering numbers did not result from differential survival or movement. A new neckband study, started in 1991, was designed to test hypotheses that the increases in wintering geese in the mid-Atlantic resulted from increasing numbers of resident geese and that the decline in migrants was related to higher harvest rates. Numbers of wintering geese continued to increase in the mid-Atlantic and declined in the Chesapeake region. Analyses of winter-banded, migrant geese indicated that 47 000 (SE = 14 000) geese per year moved from the mid-Atlantic to the Chesapeake region, thus rejecting the short-stopping hypothesis for this period. The probability of mid-Atlantic neckbanded resident geese remaining in the mid-Atlantic during winter was 0.988 (0.005). No differences in average survival were detected for migrants wintering in different regions during 1991-1994. Resident geese had higher survival than migrant geese in the Chesapeake region but not in the mid-Atlantic region. Harvest age ratios were low for Maryland and Quebec during the 1990s with record lows occurring during 1992. The only survival rate that could be estimated during the period of harvest restrictions was for 1992. Differences in survival were not detected between the periods of liberal harvest, 1985-1987, and the one year estimate under restrictive harvest. Because of the low age ratio, comparable numbers of adults were harvested during periods of restrictive and liberal regulations. Migrants appeared to be declining in all wintering regions, and residents appeared to be increasing. The different trends may be due to production differences.

Geographic Variation in Band Reporting Rates for Mallards Based on Reward Banding

We conducted a reward band study on mallards (Anas platyrhynchos) to estimate and test hypotheses about sources of variation in band reporting rate. We banded 25,398 mallards with standard and $100 reward bands (3 mallards banded with standard bands for every reward-banded mallard) during preseason (Jul-Sep), 1988. We used a series of multinomial models to model the resulting 2,776 band recoveries from 1988 to 1991. Estimates of reporting rate for males shot in 10 harvest areas ranged from 0.29 to 0.46 and averaged 0.38 (SE = 0.020). We found evidence (P < 0.01) of geographic variation in reporting rates, but not of smooth latitudinal or longitudinal gradients. There was evidence (P = 0.07) of lower reporting rates for females than males, especially in prairie Canada and the Central Flyway. Except for young males in the northern Atlantic Flyway, estimated harvest rates were lower than historical estimates, as expected from recent restrictive hunting regulations. Patterns of geographic and age-sex variation in harvest rates were similar to those obtained using historical band-recovery data.

Relationship between Waterfowl and American Coot Abundance with Submersed Macrophytic Vegetation in Currituck Sound, North Carolina

Waterfowl and American coot data collected from aerial censusing on Currituck Sound were compared during three periods: before Eurasian watermilfoil (Myriophyllum spicatum) colonization (1961–1965); during Eurasian watermilfoil infestation (1968–1977); and following the near absence of submersed macrophytic vegetation after Eurasian watermilfoil decline (1981–1990). Numbers of dabbling ducks (Anas rubripes, Anas platyrhynchos, Anas acuta, Anas americana, Anas crecca), ring-necked ducks (Aythya collaris), and American coot (Fulica americana) were significantly different in Currituck Sound (p<0.05) in at least two of these periods and were highest during Eurasian watermilfoil infestation. These species also constituted higher percentages of the Atlantic Flyway counts during Eurasian watermilfoil infestation. than in periods before or after. Numbers of snow geese (Chen caerulescens), Canada geese (Branta canadensis), and canvasbacks (Aythya valisneria) were significantly different between periods; however, these birds exhibited a consistent decline from the early to the late period. This study suggests that submersed macrophytes, specifically Eurasian watermilfoil, support increased numbers of dabbling ducks, ring-necked ducks, and American coot.

Survival of Canada Geese Banded in Winter in the Atlantic Flyway

Survival of Canada Geese Banded in Winter in the Atlantic Flyway

Influenza Viruses in Birds of the Atlantic Flyway

Isolation of type A influenza viruses from the feces of 5013 birds of 16 species was attempted during a 33-month study (1977-79). Seventy viruses were isolated from the feces of 3403 ring-billed gulls in Baltimore, Md., during 16 months of sampling. Six hemagglutinin (HA) subtypes and seven neuraminidase (NA) subtypes in 15 combinations were found. The H13N6 virus was the only subtype found each year and accounted for 40% of the isolates. The rate of isolation from gulls was 0.26% in the cold months and 3.0% in the warm months. Hemagglutination-inhibition (HI) and elution-inhibition antibody profiles reflected the presence of some but not all of the viruses isolated. In mute swans, the rates of seroconversions were 16% for HA antibody and 14% for NA antibody, whereas the viral isolation rate was 0.4% over a 3-year period. Both the H5 and the N2 subtypes, which were responsible for the lethal chicken outbreaks in 1983 in Pennsylvania, were isolated from gulls in 1978 in association with subtypes not found in the chicken virus. Also, seroconversions for the H5 HA occurred in mute swans in 1978.

Estimates of Movement and Site Fidelity Using Mark‐Resight Data of Wintering Canada Geese

Population ecologists have devoted disproportionate attention to the esti— mation and study of birth and death rates and far less effort to rates of movement. Movement and fidelity to wintering areas have important ecological and evolutionary implications for avian populations. Previous inferences about movement among and fidelity to wintering areas have been restricted by limitations of data and methodology. We use multiple observation data from a large—scale capture—resighting study of Canada Geese in the Atlantic flyway to estimate probabilities of returning to previous wintering locations and moving to new locations. Mark—resight data from 28,849 Canada Geese (Branta canadensis) banded woth individually coded neck bands in the mid—Atlantic (New York, Pennsylvania, New Jersey), Chesapeake (Delaware, Maryland, Virginia), and Carolinas (North and South Carolina) were used to estimate movement and site—fidelity. Two three—sample mark—resight models were developed and programmed using SURVIV to estimate the probability of moving among or remaining within these three wintering regions. The model (MV2) that incorporated tradition" or memory of previous wintering regions fit the data better than the model (MV1) that assumes that a first—order Markov chain described movement among regions. Considerable levels of movement occured among regions of the Atlantic flyway. The annual probability of remaining in the same region for two successive winters, used as a measure of site fidelity, was 0.710 plus or minus 0.016 (estimated mean plus or minus SE, 0.889 plus or minus 0.006, and 0.562 plus or minus 0.025, for the mid—Atlantic, Chesapeake, and Carolinas, respectively. The estimated probability of moving between years corresponded to changes in winter harshness. In warm years, geese moved north and in cold years, they moved south. Geese had a high probability of moving to and remaining in the Chesapeake. Annual changes in the movement probabilities did not correspond to annual changes in the United States Fish and Wildlife midwinter survey. Considerable numbers of geese from the Carolinas appeared to be wintering in more northerly locations (short—stopped) in subsequent winters.

Habitat Use and Movements of American Black Ducks in Winter

We determined habitat use and movement patterns of 22 female American black ducks (Anas rubripes) wintering at Chincoteague National Wildlife Refuge (NWR), Virginia, with radio telemetry and aerial survey techniques during 15 December 1985-28 February 1986. Proportional use of saltmarsh, impoundment, and natural pool habitats was greater (P 1. Habitat use was affected by the day-night cycle and a tide-ice interaction. J. WILDL. MANAGE. 53(2):390-400 American black duck populations wintering along the Atlantic Flyway have declined almost 50% since 1954 (Steiner 1984). Excessive harvest (Geis et al. 1971, Blandin 1982, Grandy 1983), acid rain (Hansen 1987), and hybridization with mallards (Anas platyrhynchos) (Heusmann 1974, Ankney et al. 1987) have been suggested as factors responsible for this decline. Others believe that loss and degradation of wintering habitat may be affecting black duck populations, although the evidence is somewhat con-

Estimated Survival Rates of Canada Geese within the Atlantic Flyway

Project personnel banded 28,849 Canada geese (Branta canadensis) with aluminum leg bands and individually coded neck bands in New York, Pennsylvania, New Jersey, Delaware, Maryland, Virginia, North Carolina, and South Carolina from 1983 to 1986. The mean annual neck band retention rate was 99.3 * 0.3 (SE)% from retrap data of previously banded geese. The annual survival rate for the flyway was 77.3 3.8% using band-recovery analyses from 1,008 recoveries of 13,331 postseason-banded geese and 70.9 ? 1.3% using mark-resight data. Annual changes in the distribution of wintering geese were caused, in part, by changes in annual survival rate. J. WILDL. MANAGE. 53(1):91-96 The changing winter distribution of Canada geese is a major problem facing managers within the Atlantic flyway (Hankla and Rudolph 1967, Trost and Malecki 1985, Malecki and Trost 1986). During the 1960's, a large percentage of wintering geese shifted northward from North and South Carolina to the Chesapeake region (Del., Md., and Va.) (Trost and Malecki 1985). The distribution of wintering geese appears to be shifting further north from the Chesapeake to the mid-Atlantic region (N.Y., Pa., and N.J.) (Fig. 1). The changing winter distribution may result from differential survival, reproduction, or movement between subpopulations or regions. Differential survival or movement may result from changes in available wintering habitat, changes in diet, proliferation of private sanctuaries, changing weather trends, and increasing numbers of resident geese decoying migrants. Our objective was to determine if changing winter distribution of Canada geese results from differential survival. We thank all state, federal, and private biologists who have banded or observed geese in the Atlantic flyway. Without their hard work, this study would not have been possible. We especially thank J. D. Nichols for assistance with the analysis, S. Sheaffer for computing assistance, and J. E. Hines for Figure 1. We also thank J. D. Nichols, S. Sheaffer, N. B. Barber, M. J. Conroy, and an anonymous referee for reviewing the manuscript. This paper is a contribution of the New York Cooperative Fish and Wildlife Research Unit: the U.S. Fish and Wildlife Service (USFWS), Cornell University, New York State Department of Environmental Conservation, and Wildlife Management Institute (USFWS contract 14-16-0009-1524) cooperate with the New York Cooperative Fish and Wildlife Research Unit.

Survival Rates of Hand-Reared Mallards Released on 2 Private Farms

I derived survival rates of hand-reared mallards (Anas platyrhynchos) released on 2 private farms in Maryland using stochastic models. Survival rates of summer-banded young for the first hunting season to the time of postseason banding in February averaged 0.29 and 0.47 for males and females, respectively. Survival rates of adults banded postseason generally were lower (f difference = -0.18, P < 0.02) than those of wild mallards banded postseason in Maryland. Survival rates of hand-reared adult males averaged 0.35; female survival rates were 0.27 at Remington Farms and 0.55 at Money Point Farm. Survival rates of handreared mallards were lower and nonhunting mortality rates higher than those of wild mallards. J. WILDL. MANAGE. 53(1):114-118 Releasing hand-reared mallards is controversial in the Atlantic Flyway (Atl. Waterfowl Counc., unpubl. min. of annu. meetings, 1979, 1980). Released birds may have traits that lead to low survival in the wild and they may contaminate the wild gene pool (Banks 1972). Previous estimates of survival rates for hand-reared mallards used early unsophisticated methods based on invalid assumptions (Brownie et al. 1985:8). My objective was to estimate survival rates, derived from stochastic models, of handreared mallards released on 2 private farms in Maryland. I thank A. G. Decker, Jr. for allowing me to use hunting and banding records, and his staff for assisting with bird banding. J. D. Nichols and the U.S. Fish and Wildlife Service's (USFWS) Bird Banding Laboratory assisted with compilation and analysis of data. Remington Arms Company, Incorporated, funded the study. STUDY AREA AND METHODS Mallard releases were made on Money Point and Remington F4rms located on Maryland's Eastern Shore. Money Point was a 95-ha grain farm, located in Cecil County on the north shore of the Sassafras River. Remington Farms was a 1,330-ha grain farm and wildlife management and demonstration area, located in Kent County, and bordered an estuarine creek of the Chester River. Money Point Farm released about 1,000 mallards annually. Each spring 80 carry-over second-year females and 20 males were selected as breeders. Ducklings were raised in a brooder house for 10 weeks, then released (about midJul) in groups on 3 ponds and the creek shore. Mallards were fed until 10 days before the start of the hunting season. Remington Farms released about 5,700 mallards annually. One-day-

Evaluation of Aerial Transect Surveys for Wintering American Black Ducks

We used an experimental aerial transect survey with stratified random sampling, to estimate the size of the population of wintering black ducks (Anas rubripes) in coastal New Jersey during 2 winters, and the coastal Atlantic Flyway (Me. to S.C.) during 4 years. Population estimates were precise (CV 2 x MWS. Because of the lack of statistical design, precision cannot be estimated. Also, because an attempt is made to survey all waterfowl habitats and species, the results are likely not precise for any 1 species. Our objectives were to design a survey to provide precise estimates of the size of the Atlantic Flyway black duck population during winter, compare our results with those of the MWS during the same periods in terms of ac' Present address: Georgia Cooperative Fish and Wildlife Research Unit, School of Forest Resources, University of Georgia, Athens, GA 30602.

Survival of Juvenile Ring-Necked Ducks on Wetlands of Different pH

Brood and duckling survival of ring-necked ducks (Aythya collaris) was examined in relation to wetland water chemistry in eastcentral Maine during 1983-85. Daily survival rates (DSR) of broods and ducklings were determined for 381 ducklings from 64 broods by counts of each brood at 6-10-day intervals during broodrearing. Twelve of 64 females lost entire broods. Only 176 of 381 (46%) ducklings survived to fledge. Brood survival for the 45-day rearing period was 0.7731; duckling survival was 0.3707. Young ducklings ( 6.1) wetlands (0.9816/day) (P = 0.049). Class IIb-III (25-45 days old) ducklings from the lowest-pH wetlands ( 6.5) had the highest DSR (0.9856) (P = 0.009). J. WILDL. MANAGE. 52(2): 169-176 Ring-necked ducks have fairly high annual harvest rates, though populations on wintering areas may be declining (Conroy and Eberhardt 1983; U.S. Fish and Wildl. Serv., Off. Migr. Bird Manage., unpubl. data). Conroy and Eberhardt (1983) reported that age ratios for ring-necked ducks harvested in fall in the Atlantic Flyway (1961-81) were lower than those from the Mississippi Flyway (1.18 vs. 1.29 young/ad). The northeast receives acidic precipitation (Cowling 1982); almost 17% of the 3,100,000 km2 of breeding area of the ring-necked duck is vulnerable to acidification and up to 34,000 pairs could be affected (Longcore et al. 1987). Wetland acidification could adversely affect waterfowl by lowering diversity or biomass of invertebrates in wetlands used by breeding adults or ducklings. Female ducks rely on protein-rich invertebrates for egg laying, and ducklings require ample protein and nutrients for growth (Swanson and Meyer 1973, Krapu 1974, Reinecke 1979). Reductions in invertebrates during broodrearing may lower survival of ducklings and reduce recruitment. Brood surveys are used to estimate production and apparent survival rates (ASR) of ducklings. However, estimates from this method overestimate production because there is no accounting for loss of entire broods (Ball et al. 1975, Reed 1975, Ringelman and Longcore 1982, Talent et al. 1983). We estimated survival rates of ring-necked duck broods and ducklings in eastcentral Maine by relocating broods at regular intervals and recording duckling attrition over time. We estimated survival rates of older and younger ducklings and related differences in survival to differences in pH and alkalinity of the broodrearing wetland. We thank A. G. LaRochelle, P. E. Malicky, C. J. Reid, D. D. Eggeman, R. R. Roy, J. R. Kelly, R. D. Stratton, J. C. Lewis, J. D. Stanton III, J. P. Gibbs, T. P. Hodgeman, and J. A. Barker for assistance with brood surveys and sorting invertebrates. T. M. Mingo and C. J. Reid identified invertebrates. K. L. Stromborg analyzed water samples. J. D. Nichols gave helpful advice during the planning stages and on analyses of survival rates. C. M. Bunck, G. W. Pendleton, P. H. Geissler, and L. M. Moyer helped with statistical analyses of invertebrate data. J. E. Hines and R. E. Munro gave programming support. Helpful comments on early drafts of this manuscript were made by J. D. Nichols, G. M. Haramis, M. A. Howe, D. H. White, M. J. Conroy, and an anonymous referee. STUDY AREA AND METHODS About 17% (15,000 km2) of the land area of Maine has low to no acid-neutralizing capacity [ANC] (i.e., sensitivity Class 1 [Norton 1980: 524]). Our study areas were selected to represent Class 1 and Class 2 (low-moderate ANC) terrain and consisted mostly of wetlands in Hancock and Washington counties in eastcentral Maine. The 66-km2 Cherryfield study area was located

Effect of the Point System on Redistributing Hunting Pressure on Mallards

Effectiveness of the point system was investigated by contrasting first-year recovery rates of mallards (Anas platyrhynchos) during the pre-point system period (1960-69) and during a point system period (1972-84). Three components were examined to investigate effectiveness of the point system: decreasing recovery rates of females, increasing recovery rates of males, and increasing the difference between male and female recovery rates. We concluded that little change in recovery rates of male and female mallards took place since initiation of the point system. Lacking a controlled experiment, it was not possible to attribute the small changes we did find to point system regulations, or to discern whether the reduction in female recovery rates was the result of the point system. J. WILDL. MANAGE. 52(1):89-94 The point system was suggested as a method for regulating the harvest of waterfowl (A. S. Hawkins and C. E. Addy, unpubl. rep., U.S. Fish and Wildl. Serv., Washington, D.C., 1971). Low point values were assigned to species or sex classes for which additional hunting pressure was desirable (e.g., drake northern pintails [Anas acuta] were assigned 10-20 points each) and high point values were assigned to those for which less hunting pressure was desired (e.g., canvasback [Aythya valisineria] were valued at 100 points). The daily bag limit was reached when a hunter bagged a bird causing the total point value of birds in possession to equal or exceed 100 points. The objectives of the point system were to afford waterfowl managers the ability to redistribute harvest among species or sexes within a species and to provide more flexible harvest regulations to increase hunting opportunities (Geis This content downloaded from 157.55.39.35 on Fri, 02 Sep 2016 04:18:09 UTC All use subject to http://about.jstor.org/terms 90 EFFECT OF POINT SYSTEM ON MALLARDS * Rexstad and Anderson J. Wildl. Manage. 52(1):1988 and Crissey 1973). The reduction in the harvest of females theoretically allowed females to contribute to the reproductive pool the following spring. Thus, a strong premise underlying the point system is that hunting mortality is additive (Nichols et al. 1984). Interest in the point system was low initially but increased rapidly as the potential advantages of the system were realized. Controversy followed, which centered on regulation enforcement. Enforcement was difficult because a hunter could initially shoot a 100-point bird but continue to hunt low-point birds (Geis and Crissey 1973). For example, 2 35-point birds and a 20point bird might subsequently be taken, and hunters could claim they shot the 100-point bird last. This procedure, known as reordering, also could apply to individuals within a hunting party. A second problem was the potential for waste of high-point birds either discarded in the marsh or deliberately not retrieved so the hunter could continue to shoot lower-point birds and thus extend the hunting opportunity. Prior to the initiation of the point system there was little incentive for hunters to leave birds in the marsh. Most states changed from a conventional bag limit to the point system by the 1971-72 hunting season in the Central Flyway and by the 197475 season in the Mississippi Flyway. Canadian provinces, the Pacific Flyway states, and many states in the Atlantic Flyway never adopted the point system. Only North Dakota in the Central and Minnesota in the Mississippi flyways retained conventional bag limits and some states (e.g., Oh.) have returned to the conventional bag limits. Initial evaluations of the point system were conducted in Colorado (Hopper et al. 1975) and Michigan (Mikula et al. 1972). Most studies were directed at hunter attitudes and acceptance (Nelson and Low 1977) and hunter performance in the field (C. F. Kimball et al., unpubl. rep., U.S. Fish and Wildl. Serv., Washington, D.C., 1971; Bishop 1973). Our objective was to determine if the point system was effective in redistributing hunting pressure toward male mallards (ranging in value from 20 to 35 points) and away from female mallards (ranging in value from 70 to 90 points). We are grateful to the Pacific Flyway Council for providing funds to conduct this analysis. We acknowledge the assistance of the U.S. Fish and Wildlife Service Bird Banding Laboratory, Laurel, Maryland and the duck hunters who reported their recovered bands. We thank T. W. Aldrich for facilitation and logistical support, and W. F. Andelt, J. C. Bartonek, K. E. Gamble, D. H. Johnson, C. F. Kimball, H. W. Miller, J. D. Nichols, and J. T. Ratti for their helpful comments on earlier versions of this manuscript.

Influence of Nutrients on Feed Intake and Condition of Captive Canvasbacks in Winter

Dramatic changes in the food habits and distribution of canvasbacks (Aythya valisineria) in Chesapeake Bay during the 1970's generated a need to evaluate the nutritional value of food items and the requirements of this species on its wintering grounds. Groups of captive canvasbacks were maintained ad libitum on 5 diets during the winters of 1978-79 and 1979-80 to evaluate the effects of varying protein and energy levels on feed intake and condition. Feed intake during the 1979-80 winter was 42% greater for those ducks fed the low energy (1,543 kcal/kg) diet than for those fed the high energy (3,638 kcal/kg) diet. Canvasbacks fed the high energy diet, however, consumed 317 kcal/bird day, whereas those fed the low energy diet consumed only 191 kcal/bird day. Body weight of males and females did not differ among groups fed different diets, but there were seasonal differences (P < 0.05) for both sexes aggregated across diets. Data from this study indicate that canvasbacks may be unable to adjust intake rates to compensate for low energy foods and subsequently may store less fat or modify behavior. However, decreased weight, feed intake, and activity of ducks fed ad libitum rations occurred in mid-winter irrespective of diet quality and appeared to be an endogenous component of their annual cycle that persists in captivity. These changes apparently have a selective advantage of increasing the probability of survival in ducks by decreasing energy expenditure during periods of winter stress. J. WILDL. MANAGE. 50(3):427-434 Aerial winter waterfowl surveys conducted by the U.S. Fish and Wildlife Service from 1955 to 1979 indicated that the winter population of canvasbacks in North America has ranged from 481,000 in 1955 to 179,000 in 1972 (Perry et al. 1981). The winter population in Chesapeake Bay (Md. and Va.) averaged 31% of the North American population and 62% of the Atlantic Flyway population. During 1955-79, numbers of canvasbacks declined substantially in Chesapeake Bay, the Atlantic Flyway, and North America (Perry et al. 1981). During the 1970's in the Atlantic Flyway, the percent of canvasbacks wintering in Chesapeake Bay decreased, whereas percentage increases occurred in New Jersey and North Carolina. Increases in New Jersey remain unexplained (Perry 1982), but increases in North Carolina may be related to better habitat conditions due to a larger number of freshwater impoundments (Perry and Uhler 1982). These wetlands provide abundant aquatic vegetation, which has traditionally been an important winter food for canvasbacks. Vegetation surveys from 1971 to 1979 showed Present address: 7 Crestwood Drive, Tolland, CT 06084. a decline in the frequency of occurrence and biomass of submerged aquatic plants in Chesapeake Bay (Kerwin et al. 1976, Bayley et al. 1978, Orth and Moore 1981, Haramis and Carter 1983). Turbidity and herbicides have been implicated in the decline of vegetation (Stevenson and Confer 1978). Two exotic aquatic plants, waterchestnut (Trapa natans) and spiked watermilfoil (Myriophyllum spicatum) were introduced into Chesapeake Bay during the 1900's and competed with native food plants (Gwathney 1945, Rawls 1975, Bayley et al. 1978). Some areas of the bay became completely covered by exotics, which restricted growth of wildcelery (Vallisneria americana) and other submerged native plants. Native waterfowl plant foods declined in abundance during the exotic plant infestations but recovered with the demise of the exotics. Waterfowl abundance on the Susquehanna Flats, in the upper bay, seemed to be inversely related to the abundance of exotic plants (Bayley et al. 1978). Habitat changes in Chesapeake Bay were reflected in a precipitous decline in vegetation as a food of canvasbacks, which occurred concurrently with an increase of mollusks as a food item (Munro and Perry 1981, Perry et al. 1981). The dramatic change in canvasback food habits

Organochlorine residues in adult mallard and black duck wings, 1981?1982

Ten organochlorine compounds were identified in pools of black duck (Anas rubripes) and mallard (A. platyrhynchos) wings from the 1981-82 hunting season. Most organochlorine compounds occurred very infrequently. Among those compounds positively identified by mass spectrometry, DDE and, secondarily, PCB had the highest frequencies of occurrence. Other compounds, positively identified and occurring less frequently, included DDT, DDD, DDMU, dieldrin, heptachlor epoxide, trans-nonachlor, cis-chlordane and mirex. Compounds looked for but not positively identified include oxychlordane, cis-nonachlor, endrin, hexachlorobenzene and toxaphene. PCB levels in black duck wings declined between the 1979-80 and 1981-82 collections. PCB levels in black duck wings from the northern region of the Atlantic Flyway were higher than those in wings from the southern region. Mean DDE residues in mallard wings declined between collections and differed among flyways and regions. PCB levels in mallard wings differed only among flyways and regions.