Geology topics

Dennis G. Raveling

Publications and source records attributed to Dennis G. Raveling.

5 recordsLinked to original sources

USGS2011

Seasonal variation in nutritional characteristics of the diet of greater white-fronted geese

We studied diet and habitat use of greater white-fronted geese ( Anser albifrons ) from autumn through spring on their primary staging and wintering areas in the Pacific Flyway, 1979–1982. There have been few previous studies of resource use and forage quality of wintering greater white-fronted geese in North America, and as a consequence there has been little empirical support for management practices pertaining to habitat conservation of this broadly distributed species. Observations of >2,500 flocks of geese and collections of foraging birds revealed seasonal and geographic variation in resource use reflective of changes in habitat availability, selection, and fluctuating physiological demands. Autumn migrants from Alaska arrived first in the Klamath Basin of California and southern Oregon, where they fed on barley, oats, wheat, and potatoes. Geese migrated from the Klamath Basin into the Central Valley of California in late autumn where they exploited agricultural crops rich in soluble carbohydrates, with geese in the Sacramento Valley feeding almost exclusively on rice and birds on the Sacramento–San Joaquin Delta primarily utilizing corn. White-fronted geese began their northward migration in late winter, and by early spring most had returned to the Klamath Basin where 37% of flocks were found in fields of new growth cultivated and wild grasses. Cereal grains and potatoes ingested by geese were low in protein (7–14%) and high in soluble nutrients (17–47% neutral detergent fiber [NDF]), whereas grasses were low in available energy (47–49% NDF) but high in protein (26–42%). Greater white-fronted geese are generalist herbivores and can exploit a variety of carbohydrate-rich cultivated crops, likely making these geese less susceptible to winter food shortages than prior to the agriculturalization of the North American landscape. However, agricultural landscapes can be extremely dynamic and may be less predictable in the long-term than the historic environments to which geese are adapted. Thus far greater white-fronted geese have proved resilient to changes in land cover in the Pacific Flyway and by altering their migration regime have even been able to adapt to changes in the availability of suitable forage crops.

Pacific Flyway↗

USGS1996

Migration, fidelity, and use of autumn staging grounds in Alaska by Cackling Canada Geese Branta canadensis minima

Cackling Canada Geese were studied annually (1985-88) on autumn migration staging areas in Alaska during a period of rapid population growth. Geese concentrated at two estuaries (Ugashik Bay and Cinder Lagoon) along the north side of the Alaska Peninsula. Birds arrived on the staging areas in late September, numbers peaked during mid-October, and departure occurred by late October or early November. Annual peak counts combined for the two staging areas ranged from 16,000-54,000 geese, or from 23-120% of the autumn population index. Up to 30,000 geese were recorded at each estuary, but relative use of the two staging areas varied among years. Within-year fidelity to staging areas was high; only three of 242 neck-banded geese seen more than once were observed at both areas within a season. Between-year fidelity to staging areas was highest among hatching-year females (11 of 11) and adult males (14 of 17), lowest among hatching-year males (4 of 9), and intermediate among adult females (18 of 28). Use of the two staging areas was independent of family status, reproductive status, and age. Late arrivals on the staging areas consisted of a higher proportion of single and paired birds than of geese in family groups. Most geese departed the staging grounds with the onset of freezing conditions and the passage of low pressure systems that produced winds favourable for migration. Transoceanic flights to the wintering grounds in Oregon and California were completed in about 48 h. During years with mild weather on the breeding grounds and years with early freezing conditions on the staging areas, few geese staged on the Alaska Peninsula, indicating that geese can sometimes obtain sufficient energy reserves to migrate directly from the breeding grounds without stopping on the staging areas. Only 25% of the area used for staging is legally protected. Use of unprotected areas may become increasingly important if the population continues to increase.

Alaska↗

USGS1992

Survival of cackling Canada geese, 1982-1988

We estimated seasonal and annual survival rates of cackling Canada geese ( Branta canadensis minima ) for the period 1982-1989 to identify periods of high mortality and assess effects of harvest management decisions. We tested hypotheses about age- and sex specific variation in survival, seasonal variation in survival rates, and variation in survival between years in which hunting seasons were open and closed. Geese were marked with individually identifiable neckbands and observed from autumn through spring. We used these data to estimate survival rates for 3-month periods in early (EW) and late (LW) winter and a 6-month period in summer (SU). Mean annual survival rates of immature females were lower than those of adults over the entire study. Survival rates of immature males were lower than those of adults during the 2 years with sport hunting seasons. We found no evidence of sex-specific differences in seasonal or annual survival rates of immature geese. Mean survival rates of adult males and females were similar during EW and LW, but there was evidence of higher survival of females during SU. Annual survival rates of adult females were higher than those of adult males. Mean annual survival rates of adult females and immatures of both sexes were lower in the years during which sport hunting was permitted. Tests for different survival rates in years before and after an agreement with the Eskimos to cease summer hunting yielded equivocal results.

Alaska, California↗

USGS1989

Body composition and weight dynamics of wintering greater white-fronted geese

Adult greater white-fronted geese ( Anser albifrons frontalis ) wintering in southern Oregon and California increased or maintained body weight in autumn, lost weight from autumn through winter, and rapidly increased in weight before spring migration in late April. We documented significant annual differences in body weights for both sexes. We related seasonal changes in body weight to changes in lipid levels, which were lowest (12-13% of wet wt in M and F) in mid-March and highest in late April (24% in F). Greater white-fronted geese maintained lipid levels during winter similar to those reported for large subspecies of Canada geese ( Branta canadensis ), and greater than those reported for small subspecies of Canada geese and other small species of geese. Protein content of carcasses varied significantly in females; i.e., lowest in early October and highest in late October and late April. Differences among species in patterns of weight change and body composition during winter seem to be related to social organization, body size, food type, and foraging behavior. Females left spring staging areas weighing relatively less than most other species of geese and may have benefited from foraging opportunities on the nesting grounds.

California, Oregon↗

USGS1984

Breeding biology of Pacific white-fronted geese

Nesting ecology of Pacific white-fronted geese ( Anser albifrons frontalis ) was studied on a 9.9-km 2 area on the Yukon-Kuskokwim (Y-K) Delta, Alaska, during 1977-79. Availability of nesting habitat varied considerably among years because of differences in time of snow- and icemelt. Mean clutch size was 3.7 eggs in the late spring thaw year and 5.2 and 5.7 eggs in early snowmelt years. Peak (and duration) of nest initiation was 1-2 June (16 days) in the late spring and 15-18 May (20-21 days) during early springs. When nest sites were available early, the time interval between arrival and date of nest initiation closely approximated the time required for rapid yolk development. This suggests that whitefronts may be physiologically prevented from nesting earlier in such years. The duration of nest initiation was comparable to that of other goose species nesting on the Y-K Delta, but longer than for goose populations of several species nesting farther north or in the midcontinent. Overall, 68% of whitefront nests were in lowland habitat, 23% in intermediate habitat, and 10% in upland habitat, but habitat use varied significantly between early and late years. Whitefronts most commonly nested on slough banks (55%), lake shores (23%), and grass-sedge meadows (11%). A quantitative description of vegetation associated with nest sites is given. Major causes of nest destruction were flooding (28%) and predation (9%). Nesting success over the 3-year period averaged 62%.

Alaska↗