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Daniel B. Stotts

Publications and source records attributed to Daniel B. Stotts.

15 recordsLinked to original sources
USGS2002

Breeding productivity of Smith Island black ducks

We investigated the breeding performance of American black ducks (Anas rubripes) on Smith Island, Chesapeake Bay, to improve our understanding of island black duck breeding ecology and to make management recommendations to enhance productivity. During 1995-96, we implanted 56 female black ducks with 20-g radio transmitters and tracked 35 of the individuals through the breeding season to locate nests, determine nest fate, and identify brood habitat. We also increased preseason banding efforts and compared capture characteristics over 12 years with those from the Deal Island Wildlife Management Area, a banding site on the mainland of Tangier Sound. A low rate of nesting (37%), lack of renesting, and poor hatching success (31%) indicated that island salt marsh habitats present a harsh environment for breeding black ducks. Black ducks located 11 of 13 nests (85%) in black needlerush (Juncus roemerianus) marsh where they were vulnerable to flooding from extreme tides and to egg predators. No nests were found on forested tree hammocks, a feature that distinguishes Smith Island from nearby South Marsh and Bloodsworth Islands. Nest predators included red foxes (Vulpes vulpes), herring gulls (Larus argentams), fish crows (Corvus ossifragus), and, potentially, Norway rats (Rattus norvegicus). Unlike mainland red foxes, foxes radio tracked on Smith Island were found to be capable swimmers and effective low marsh predators. We found shoreline meadows of widgeon grass (Ruppia maritima) to be important foraging sites for black ducks and suspected that the virtual absence of fresh water in this high salinity environment (1217+ ppt) to incur some cost in terms of growth and survival of ducklings. Preseason bandings revealed a high proportion of banded adults and a strong positive correlation in age ratios with the Deal Island banding site. This latter finding strongly suggests a negative universal effect of storm tides on nest success for Tangier Sound black ducks. Management to reduce nest predators, especially gulls and foxes, likely will have the greatest immediate benefit for island breeding black ducks.

Book chapter↗
USGS2002

The midwinter survey of black ducks, locally and regionally

The Midwinter Waterfowl Inventory (MWI) has been conducted consistently in Maryland since 1955 and in Virginia since 1957. Maryland currently focuses surveys in 30 segments along the Chesapeake Bay, Potomac River, and Atlantic Coast, whereas Virginia focuses on 22 segments centered over the eastern shore of Chesapeake Bay and along the tidewater areas of Back Bay and western shore tributaries. Until 1980, the survey along the Potomac River was shared and sometimes duplicated by Maryland and Virginia but now is flown entirely by Maryland. The MWI number of black ducks wintering in Maryland shows a decreasing trend until 1983 when the trend reversed, possibly in response to restrictive hunting regulations. In Virginia, the MWI index of black ducks reached its lowest point in 1965 at just under 4,000 ducks, steadily increased to a peak of 18,000 black ducks in 1981, then began a steady decline to the present. The number of black ducks on the Potomac River reached a low of 400 ducks in 1971, 1984, and 1985 but generally attracts 500-1,500 ducks each year. The distribution of black ducks in the Bay has also changed from upper Bay areas to mid-Bay eastern shore sites and the Potomac River. Whereas the decline in black ducks seems to be related to hunting, the redistribution of black ducks in Maryland seems to be associated with habitat changes in water quality and the decline of submerged aquatic vegetation.

Book chapter↗
USGS2000

Survival of American black ducks radiomarked in Quebec, Nova Scotia, and Vermont

We monitored survival of 397 radiomarked juvenile American black ducks (Anas rubripes) distributed among Les Escoumins ( n = 75) and Kamouraska, Quebec ( n = 84), Amherst Point, Nova Scotia ( n = 89), and a site on the Vermont-Quebec border ( n = 149) during autumn 1990 and 1991. Eighty-six percent (215 of 250) of all confirmed mortalities during the study was from hunting; 72% of marked ducks were shot and retrieved and 14% were shot and unretrieved. We tested for differences in survival in relation to sex, body mass, year (1990-91, 1991-92), and among the 4 locations for each of 2 monitoring periods (early, EMP; late, LMP). With data from the EMP for Vermont-Quebec in 1990 and 1991, Les Escoumins in 1990, and Amherst Point in 1991, survival of hatching-year (HY) males and females did not differ ( P = 0.357). For sexes combined for the EMP, survival of ducks was greater in 1991 than 1990 ( P = 0.086), and differed among locations ( P = 0.013). Survival (years combined) was greater at Amherst Point than at Kamouraska ( P = 0.003) and Vermont-Quebec ( P = 0.002) during the EMP. The highest survival rate at Amherst Point (0.545 ± 0.056 [SE]) was associated with the latest date (8 Oct) of season opening; the lowest survival rate (0.395 ± 0.043) was at the Vermont-Quebec border, where hunter numbers and activity were greatest. For the LMP, no interaction between years and locations was detected ( P = 0.942), and no differences in survival existed between years ( P = 0.102) and among locations ( P = 0.349). No association was detected between body mass at capture and survival of combined males and females during the EMP ( P = 0.572) or during the LMP ( P = 0.965). When we censored hunting losses for combined years for each period, EMP or LMP, all survival estimates exceeded 0.800 (0.809-0.965). These data emphasize need for an improved harvest strategy for American black ducks in North America to allow for increases in breeding populations to achieve population goals.

Nova Scotia, Quebec, Vermont↗
USGS2000

Capturing American black ducks in tidal waters

We modified conventional, funnel-entrance dabbling duck bait traps to increase captures for banding of American Black Ducks (Anas rubripes) in tidal saltmarsh habitats of Smith Island, Maryland, one of the few remaining strongholds for breeding Black Ducks in the Chesapeake Bay. Traps and trapping techniques were adapted to tidal creeks and refined to improve capture rate, reduce mortality, and minimize interference by gulls. Best results were achieved by synchronizing trapping with predawn, low-tide foraging patterns of Black Ducks. Trap entrances were critical to retaining ducks, and use of loafing platforms reduced overall mortality to 3% of captures per year. We captured 3071 Black Ducks during the 14-year period, 1984-199

Journal of Field Ornithology↗
USGS1999

Aspects of chick growth in Gull-billed Terns in coastal Virginia

Because of concerns about apparent population declines and low productivity of Gull-billed Terns (Sterna nilotica) along the coast of Virginia, we investigated whether food limitations may result in retarded growth rates of young. Several colonies of Gull-billed Terns were monitored from May to July each year from 1994 to 1996 on both sandy barrier islands and marsh/shellpile islands in coastal Virginia. Nests were visited one to three times a week to monitor clutch size and hatching success, and enclosures were installed around selected nests to monitor chick growth from hatching to at least two weeks of age. When comparing chick growth, we found significant year, habitat and hatch order effects. Chicks from marsh shellpiles had higher mass and culmen growth rates than did those from barrier islands, and first-hatched (A) chicks had significantly higher culmen growth rates than did second-hatched (B) chicks. Year effects were only found for mass growth rates. Growth rates of Gull- billed Terns in these Virginia colonies seem to be low relative to those of six other North American tern species from other geographic areas. These findings suggest that growth rates of young Gull-billed Terns, as well as other reproductive parameters, need to be examined in detail in other coastal areas such as Texas, where the species is more abundant, to determine whether our growth results are species- or region-specific.

Waterbirds↗
USGS1999

Aspects of hatching success and chick survival in Gull-billed Terns in coastal Virginia

Because of a long-term population decline in Gull-billed Terns (Sterna nilotica) nesting along the coast of Virginia, we began a three year study in 1994 to monitor hatching success and survival of Gull-billed Tern chicks at several Virginia colony sites. Colonies were located on either small, storm-deposited shellpiles along marsh fringes or large, sandshell overwash fans of barrier islands. Nests were monitored one to three times a week for hatching success, and enclosures were installed around selected nests to monitor chick survival from hatching to about two weeks of age. Hatching success was lower in marsh colonies than island colonies, and was lower in 1995 than in 1994 and 1996, primarily because of flooding. The average brood size of nests where at least one chick hatched was 1.99 chicks. Survival rates of chicks to 14 days depended on hatch order and year but not brood size (one vs. two or more) or time of season. A-chicks had higher survival rates than B-chicks and third-hatched C-chicks (0.661 compared to 0.442 and 0.357, respectively). The year effect was significant only for A-chicks, with lower survival in 1994 (0.50) than in 1995 (0.765) or 1996 (0.758). Overall, productivity was low (0.53 chick per nest) compared to estimates for colonies in Denmark, and was attributable to nest flooding by spring and storm-driven high tides and chick predation, presumably mostly by Great Horned Owls (Bubo virginianus).

Waterbirds↗
USGS1998

Modeling colony site dynamics: A case study of gull-billed terns ( Sterna nilotica ) in coastal Virginia

We developed a Markov process model for colony-site dynamics of Gull-billed Terns ( Sterna nilotica ). From 1993 through 1996, we monitored breeding numbers of Gull-billed Terns and their frequent colony associates, Common Terns ( Sterna hirundo ) and Black Skimmers ( Rynchops niger ), at colony sites along 80 km of the barrier island region of coastal Virginia. We also monitored flooding events and renesting. We developed the model for colony survival, extinction, and recolonization at potential colony sites over the four-year period. We then used data on annual site occupation by Gull-billed Terns to estimate model parameters and tested for differences between nesting substrates (barrier island vs. shellpile). Results revealed a dynamic system but provided no evidence that the dynamics were Markovian, i.e. the probability that a site was occupied in one year was not influenced by whether it had been occupied in the previous year. Nor did colony-level reproductive success the previous season seem to affect the probability of site occupancy. Site survival and recolonization rates were similar, and the estimated overall annual probability of a site being occupied was 0.59. Of the 25 sites that were used during the four-year period, 16 were used in one or two years only, and only three were used in all four years. Flooding and renesting were frequent in both habitat types in all years. The frequent flooding of nests on shellpiles argues for more effective management; augmentation with shell and sand to increase elevations as little as 20 cm could have reduced flooding at a number of sites. The low colonysite fidelity that we observed suggests that an effective management approach would be to provide a large number of sand and/or shellpile sites for use by nesting terns. Sites not used in one year may still be used in subsequent years.

The Auk↗
USGS1996

Reproductive success, growth and survival of black-crowned night-heron ( Nycticorax nycticorax ) and snowy egret ( Egretta thula ) chicks in coastal Virginia

We studied reproductive success, growth, and survival of Black-crowned Night-Heron ( Nycticorax nycticorax ) and Snowy Egret ( Egretta thula ) chicks in two mixed-species heronries on marsh islands in Chincoteague Bay, Accomack County, Virginia in 1992 and 1993. We attached radio transmitters with mortality sensors to the oldest chicks (A-chicks) in 11 to 22 nests of both species to monitor survival during the mid- to late nestling period and into the postnesting dispersal period. For both species, we found significant differences between 1992 and 1993 in growth rates and survival. Mass growth rates of chicks were higher in 1993 than in 1992 for both species. Culmen-length growth rates varied significantly due to year-colony effects for night-herons, but only for hatching order for egrets. Differences in survival rates due to hatching order were found for the egrets in both years, but were found only in 1992 for night-herons. As with mass growth rates, survival of chicks was higher in 1993 than 1992. Survival of radio-marked A-chicks did not differ between species or years for the period from hatching to fledging or from fledging through the end of the study (ca. two months postfledging). Survival ranged from 0.80 to 1.00 from the time radio transmitters were attached (ca. two weeks of age) until dispersal age (53-55 days for egrets; 55-60 days for night-herons). After birds left the colony, survival rates were lower during the next 40 to 55 days, ranging from 0.25 to 0.60. These results suggest that, at least for Snowy Egrets, A-chicks may be buffered from annual variations in food conditions, but that growth and survival of other brood members may provide a barometer of local conditions. Despite problems of variability in measurement, some of these parameters show promise as bioindicators of estuarine conditions. We recommend that a cost-efficient wading-bird monitoring program would include: (1) estimating numbers of nesting birds of selected species (e.g. Snowy Egrets) at particular estuaries, and (2) monitoring "initial brood sizes" and survival of young to at least two weeks of age in a sample of nests for each focal species. However, additional biomonitoring (e.g. marsh forage fish, contaminant loads) is necessary to evaluate how well top trophic-level organisms such as fish-eating birds respond to changes in estuarine production or quality.

The Auk↗
USGS1996

Dispersal and habitat use by post-fledging juvenile snowy egrets and black-crowned night-herons

We studied the postfledging dispersal movements and habitat use of juvenile Snowy Egrets (Egretta thula) (SNEG) and Black-crowned Night-Herons (Nycticorax nycticorax) (BCNH) in coastal Virginia using a dye (picric acid) and radiotelemetry. Results from monitoring radiomarked birds revealed significant differences both years between species, with SNEGs dispersing more widely than BCNHs. BCNH juveniles usually remained south of Delaware, but SNEGs often moved into Delaware and southern New Jersey. The maximum dispersal distance found for a SNEG was ca 340 km north of the natal colony. Temporal patterns of movement followed logistic relationships, with rapid initial movements, but relatively few movements after about 23 weeks for most birds. Cumulative distances moved by juvenile SNEGs during AugustSeptember differed from 1992 to 1993. No such year difference was found for BCNHs. Compared to SNEGs, BCNHs used man-made impoundments relatively more often than natural wetlands; however no quantitative assessment of habitat preferences could be made.

The Wilson Bulletin↗
USGS1992

Comparative productivity of American black ducks and mallards nesting on Chesapeake Bay Islands

The authors estimated laying dates, clutch sizes, and nest success rates of sympatrically breeding populations of American black ducks (Anas rubripes ) and mallards (Anas platyrhynchos ) on Chesapeake Bay islands between 1986 and 1989. Neither average laying date nor clutch size differed between black ducks and mallards. Nest success rates were higher for mallards in 2 of 4 years, but were area dependent.

Canadian Journal of Zoology↗
USGS1991

Open marsh water management in the mid-Atlantic region: Aerial surveys of waterbird use

Nine marsh sites were selected in Maryland, Delaware, and New Jersey to assess the importance of ponds created by Open Marsh Water Management (OMWM) to migratory birds. At eight of the nine sites, OMWM ponds were paired with areas of similar-sized natural ponds. Eleven aerial surveys were conducted, mostly in fall and winter of 1987 and 1988 to compare relative use of ponds and sites by black ducks (Anas rubripes), other waterfowl, shorebirds, wading birds, gulls, and other species of birds. We noted a high degree of variation in bird use. Seasonal effects were significant, but treatment (OMWM vs. natural ponds) effect was not. Water/marsh (W/M) area ratio was positively correlated with waterfowl and black ducks, but pond number was not. Larger ponds (>0.25 ha) tended to be used more than smaller ponds by most bird species.

Delaware, Maryland, New Jersey, Virginia↗
USGS1991

Historical changes in laying date, clutch size, and nest success of American black ducks

The breeding population of American black ducks ( Anas rubripes ) on Chesapeake Bay has declined over the past 30 years. We tested whether there have been changes in laying date, clutch size, and nest success of breeding black ducks on islands in Chesapeake Bay between the 1950's and 1980's. None of these variables differed significantly between decades, suggesting that other factors must be responsible for the decline in locally breeding black ducks.

Maryland, Virginia↗
USGS1988

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 < 0.20) on a flyway basis, whereas individual strata (states) had coefficients of variation of 0.16-0.71. Population estimates agreed with the conventional mid-winter waterfowl surveys (MWS) for all 4 years (MWS within 95% CI of N). We recommend continuing these surveys to provide precise and statistically defensible population estimates for black ducks. Additional improvements in precision may be achieved using recent developments in estimation such as Bayesian techniques. Techniques to decrease bias through air-ground comparisons are likely to be expensive and will require more development. Air-ground comparisons can probably be justified if there is a demonstrable need for an estimate of the absolute size of the black duck population versus an index.

Connecticut, Delaware, Maine, Maryland, Massachuse↗
USGS1987

Winter movements of American black ducks in relation to natural and impounded wetlands in New Jersey

Radio telemetry was used to follow the movements and habitat use of female American Black ducks (Anas rubripes) trapped at Brigantine Division. Edwin B. Forsythe NWR (BNW) during three field seasons (1983-1896). Use of the BNWR impoundments was strongly associated with open vs. closed hunting seasons and with presence or absence of ice cover. Black ducks primarily used the impoundments for daytime roost sites and fed in saltmarsh areas at night during the hunting season. Following the hunting season use generally dispersed to saltmarsh and inland freshwater habitats. Freeze-up of the impoundments resulted in dispersal of black ducks to saltmarsh, inland freshwater, or areas to the south of New Jersey. We conclude that the BNWR impoundments only partially meet the habitat requirements of wintering black ducks. Access to saltmarsh habitats for feeding, and to inland freshwater habitats during periods of hard freeze, may be critical. The utility of the BNWR impoundments to black ducks, needs to be considered in conjunction with the availability of these other important habitats.

Book chapter↗