Geology topics

David H. Ward

Publications and source records attributed to David H. Ward.

101 records · Page 6Linked to original sources

USGS1997

Seasonal and annual survival of adult Pacific brant

Declining mid-winter counts of Pacific brant ( Branta bernicla nigricans ) and reduced numbers of nesting birds on their main breeding grounds prompted us to assess factors that may be limiting recovery of this population. We estimated seasonal and annual survival rates of adult brant in 1986-93 from resightings of leg-banded birds. Brant were banded at a major colony on the Yukon-Kuskokwim Delta, Alaska (Y-K Delta) in 1986-92, and resighted there in 1987-93 as well as at major fall and spring migration and wintering areas in 1990-93. Seasonal survival was the same for males and females. Mean monthly survival rate was lowest (P ≤ 0.05) in late spring migration (15 Apr-1 Jun), the period of greatest subsistence harvest on the breeding grounds, and highest in winter (1 Jan-1 Mar), the period of greatest sport harvest. Annual survival rate did not vary among years (F = 0.51; 5, 718 df; P = 0.91) and averaged 0.840 (SE = 0.031) from 1986 to 1993. Subsistence harvest has contributed to low population levels of Pacific brant.

Alaska↗

USGS1997

Testing for handling bias in survival estimation for black brant

We used an ultrastructure approach in program SURVIV to test for, and remove, bias in survival estimates for the year following mass banding of female black brant ( Branta bernicla nigricans ). We used relative banding-drive size as the independent variable to control for handling effects in our ultrastructure models, which took the form: S = S 0 (1 - α D), where α was handling effect and D was the ratio of banding-drive size to the largest banding drive. Brant were divided into 3 classes: goslings, initial captures, and recaptures, based on their state at the time of banding, because we anticipated the potential for heterogeneity in model parameters among classes of brant. Among models examined, for which α was not constrained, a model with α constant across classes of brant and years, constant survival rates among years for initially captured brant but year-specific survival rates for goslings and recaptures, and year- and class-specific detection probabilities had the lowest Akaike Information Criterion (AIC). Handling effect, α , was -0.47 ± 0.13 SE, -0.14 ± 0.057, and -0.12 ± 0.049 for goslings, initially released adults, and recaptured adults. Gosling annual survival in the first year ranged from 0.738 ± 0.072 for the 1986 cohort to 0.260 ± 0.025 for the 1991 cohort. Inclusion of winter observations increased estimates of first-year survival rates by an average of 30%, suggesting that permanent emigration had an important influence on apparent survival, especially for later cohorts. We estimated annual survival for initially captured brant as 0.782 ± 0.013, while that for recaptures varied from 0.726 ± 0.034 to 0.900 ± 0.062. Our analyses failed to detect a negative effect of handling on survival of brant, which is consistent with an hypothesis of substantial inherent heterogeneity in post-fledging survival rates, such that individuals most likely to die as a result of handling also have lower inherent survival probabilities.

Alaska, California↗

USGS1996

Black brant from Alaska staging and wintering in Japan

Black brant (Branta bernicla nigricans) nest in colonies in arctic Canada, Alaska, and Russia (Derksen and Ward 1993, Sedinger et al. 1993). Virtually the entire population stages in fall at Izembek Lagoon near the tip of the Alaska Peninsula (Bellrose 1976) before southward migration (Dau 1992) to winter habitats in British Columbia, Washington, Oregon, California, and Baja California (Subcommittee on Black Brant 1992). A small number of black brant winter in Japan, Korea, and China (Owen 1980). In Japan 3,000–5,000 brant of unknown origin stop over in fall, and a declining population (<1,000) of birds winter here, primarily in the northern islands (Brazil 1991, Miyabayashi et al. 1994). Here, we report sightings of brant in Japan that were marked in Alaska and propose a migration route based on historical and recent observations and weather patterns.

Alaska↗

USGS1995

Survival estimation and the effects of dependency among animals

Survival models assume that fates of individuals are independent, yet the robustness of this assumption has been poorly quantified. We examine how empirically derived estimates of the variance of survival rates are affected by dependency in survival probability among individuals. We used Monte Carlo simulations to generate known amounts of dependency among pairs of individuals and analyzed these data with Kaplan-Meier and Cormack-Jolly-Seber models. Dependency significantly increased these empirical variances as compared to theoretically derived estimates of variance from the same populations. Using resighting data from 168 pairs of black brant, we used a resampling procedure and program RELEASE to estimate empirical and mean theoretical variances. We estimated that the relationship between paired individuals caused the empirical variance of the survival rate to be 155% larger than the empirical variance for unpaired individuals. Monte Carlo simulations and use of this resampling strategy can provide investigators with information on how robust their data are to this common assumption of independent survival probabilities.

Journal of Applied Statistics↗

USGS1995

Effects of harness-attached transmitters on premigration and reproduction of Brant

Radio transmitters are an important tool in waterfowl ecology studies, but little is known about their effects on free-ranging geese. We attached transmitters to female brant ( Branta bernicla nigricans ) to investigate migration schedules at a fall staging area, return rates to nesting grounds, and nesting rates of returning females in subsequent breeding seasons. Radio-tagged females (n = 62) carried either 35-g back-mounted transmitters attached with ribbon harnesses, or 26- or 32-g back-mounted transmitters affixed with plastic-coated wire harnesses (Dwyer 1972). Arrival and departure schedules at Izembek Lagoon, Alaska, did not differ (P > 0.05) between radio-tagged females and the entire population in 1987-89. Color-banded females with transmitters returned to the breeding colony in subsequent nesting seasons (1988-92) at a lower (P ≤ 0.003) rate (≤4%) than color-banded females without transmitters (57-83%). The 1 returning color-banded female with a transmitter did not breed, while an average 90% of the returning color-banded females without transmitters nested in subsequent breeding seasons (P = 0.005). Back-mounted, harness-attached transmitters may bias data in studies of waterfowl behavior, productivity, and survival.

Alaska↗

USGS1994

Response of staging brant to disturbance at Izembek Lagoon, Alaska

Human disturbance of migrating waterfowl concerns managers of wildlife populations and refuges. Human disturbance may reduce food intake through interruption of foraging bouts or by displacement from feeding areas (Madsen 1985, Belanger and Bedard 1989), and it may increase energy expenditure from additional time in flight (Korschgen et al., 1985). Reduced food intake and increased energy expenditure can affect the ability of waterfowl to acquire nutrient reserves for successful migration (Fredrickson and Drobney 1979, Davis and Wiseley 1974, Belanger and Bedard 1990). Furthermore, nutrient reserves acquired during fall migration may influence overwinter survival (Haramis et al. 1986). Over 90% of the Pacific Flyway population of brant (Branta bernicla nigricans) annually migrates to the Izembek Lagoon, Alaska and adjacent areas in fall (Bellrose 1976, Reed et al. 1989). During the 4- to 10-week staging period, brant feed predominantly on energy-rich common eelgrass ( Zostera marina ) prior to a transoceanic flight to coastal wintering areas in Washington, Oregon, California, and Mexico (Hansen and Nelson 1957, Morehouse 1974, Bellrose 1976). The lzembek Lagoon, a wetland of international importance (Smart 1987), also is a major staging area for Canada geese ( Branta canadensis taverneri ), emperor geese ( Chen canagica ), and other waterbirds (Ward and Stehn 1989). Brant are disturbed by aircraft and other human activities. Jones and Jones (1966) noted that aircraft caused brant to take flight in fall at the Izembek Lagoon. Aircraft influence movements of molting brant and evoke escape responses (Derksen et al. 1979, Jensen 1990). Aircraft, boats, and hunters affect distribution of wintering brant and cause premature departures from feeding areas (Owens 1977, Kramer et al 1979, Henry 1980). However, few data have been published concerning the extent to which disturbance affects behavior of fall-staging brant. Our objective was to measure current disturbance levels and to determine the extent to which disturbance affects the behavior of brant at the Izembek Lagoon during fall. This baseline information is needed to monitor any future changes in these levels and to provide guidelines for alleviating conflicts where increased human activities cause excessive disturbance.

Alaska↗

USGS1994

Management of Pacific brant: Population structure and conservation issues

Pacific brant ( Branta bernicla ) nest from the Yukon-Kuskokwim (Y-) Delta in southwestern Alaska along the coast of North America to the central Canadian arctic (Pacific Flyway Subcommittee on Pacific Brant 1992) (Figure 1). Birds from this population also nest in the Canadian arctic islands south of Prince Patrick Island and on the coast of the Chukotka Peninsula. Brant nest principally in colonies associated with productive river deltas but isolated nests and small aggregations are common, especially in the arctic. Most Pacific brant breed on the Y-K Delta (Sediger et al. 1993).

Transactions of the North American Wildlife and Na↗

USGS1993

Current status and recent dynamics of the Black Brant Branta bernicla breeding population

We summarize current knowledge about the distribution of Pacific Black Brant and recent dynamics of colonies, particularly on the Yukon-Kuskokwim (Y-K) Delta, Alaska. About 20,000 nests are required to produce the number of young in the autumn flight using estimates of clutch size, hatching success and gosling survival based on colonies on the Y-K Delta. More than 80% of the nests in the population can be accounted for currently on the Y-K Delta. Most moulting individuals that did not breed, or were unsuccessful, are unaccounted for in late summer. Numbers of Black Brant nesting in major colonies on the Y-K Delta declined >60% in the early 1980s, most likely as a result of local subsistence harvest combined with predation by arctic foxes. Effective management of this population requires a better understanding of the distribution of breeding and moulting birds, the importance of breeding habitat to colony dynamics and the role of both sport and subsistence harvest in population dynamics.

Wildfowl↗

USGS1993

Status of Pacific Black Brant Branta bernicla nigricans on Wrangel Island, Russian Federation

Abundance, distribution, and habitat selection of breeding and moulting Pacific Black Brant were studied on Wrangel Island in 1989-91. Two nests and <10 family flocks of Brant were found during ground searches in previously known nesting areas. The breeding population has declined from 1000-2000 pairs to probably <100 pairs. An estimated 4200 50 (Cl) moulting Brant were counted during the first aerial and photographic survey of the island in 1990. This population includes moult migrants from Alaska and mainland Russia. Most (67%) of the moulting flocks were concentrated in freshwater lakes and usually within 2 km of the coast. Lakes with low relief shorelines and adjacent preferred grasses were important habitats used by moulting birds. Breeding and moulting populations of Wrangel Island Brant are dependent on Izembek Lagoon Alaska, in autumn and disperse over the rest of eastern Pacific Flyway in winter and spring.

Wrangel Island↗

USGS1993

Life history strategies and habitat needs of the black brant

The black brant is a sea goose that depends on coastal habitats from high arctic nesting sites in Canada, Alaska, and Russia to wintering areas in the Pacific coastal states, the Baja California peninsula, and mainland Mexico estuaries. Population estimates are based on aerial surveys in Mexico, California, Oregon, and Washington during mid-winter. Despite much annual variability in estimates, a plot of the counts from 1964 to 1992 reveals a significant downward trend in the winter populations (Fig. 1). Three of four major colonies on the Yukon-Kuskokwim (Y-K) delta declined an average of 60% during the first half of the 1980’s. This is significant because about 79% of the world population of the black brant nest in these colonies (Table). Because few other breeding colonies have been consistently monitored, we have little understanding of their dynamics.

Fish and Wildlife Leaflet↗

USGS1989

Autumn use of Izembek Lagoon, Alaska, by brant from different breeding areas

Thirty-three adult brant ( Branta bernicla ) were radiomarked at 4 widely separated areas of the western Canadian arctic and 1 area in western Alaska during June-August 1987. Their use of the Izembek Lagoon on the Alaska Peninsula was monitored through the 1987 fall staging period (Sep-Dec). Eighty percent of the brant (n = 33), including ≥50% of individuals from each of the marking areas, were located at Izembek Lagoon. The mean arrival time for brant marked nearest to Izembek (the Yukon-Kuskokwim Delta [YK], Alas. [900 km away]) was 18 September, followed by those from the Mackenzie Delta, Northwest Territories, (3,500 km away) on 26 September, and brant from Victoria, Melville, and Prince Patrick islands, Northwest Territories [NT], (approx 4,500 km away) on 3 October. The mean duration of their stay at Izembek was 49 days. Within the 48-km-long lagoon there was considerable segregation between black brant ( B. b. nigricans ) and gray-bellied brant (intermediate between black brant and B. b. hrota ).

Alaska↗