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R. L. Jarvis

Publications and source records attributed to R. L. Jarvis.

9 recordsLinked to original sources
USGS1997

Relationship between waterfowl nutrition and condition on agricultural drainwater ponds in the Tulare Basin, California: Waterfowl body composition

We examined carcass composition and proximate food composition of ruddy ducks ( Oxyura jamaicensis ), northern shovelers ( Anas clypeata ), and northern pintails ( Anas acuta ) wintering on agricultural drainwater ponds in California during 1983–84. Lipids varied seasonally in northern shovelers and northern pintails. Protein did not fluctuate except in ruddy ducks whose protein mass increased over winter, suggesting that some protein was catabolized prior to arrival on wintering areas or that a buildup of protein occurred prior to spring migration. Waterfowl diets varied among species and time, but the nutritional composition of the diets was relatively stable. Ruddy ducks and shovelers consumed mostly animal foods rich in protein (53–60%) and low in Nitrogen Free Extract (NFE) (1–7%). Pintail diets contained more NFE (23–38%) and less protein (14–38%) because of greater consumption of plant foods. Nutritional composition of pintail diets varied with lower protein consumption occurring from November through January.

California↗
USGS1992

Ecology of band-tailed pigeons in Oregon

The ecology of band-tailed pigeons ( Columba fasciata ) was investigated in western Oregon to assess the roles of survival and recruitment to population status and the relation of food, minerals, and diet to reproduction strategy. Band-tailed pigeons congregated at mineral deposits to consume minerals from mid-June to mid-September. Males generally arrived and departed between daylight and 1000 h and females between 0930 and 1200 h, the inverse of the nest attentive schedules for the sexes. The pigeons used one or several adjacent mineral sites throughout the summer and most returned to the same mineral site in subsequent years. Band-tailed pigeons were resident from April through September; migration apparently did not begin before late September. Three indirect sources of evidence indicated that fledging began in June, reached a peak in mid- August, and continued until late September. Second year (SY) band-tailed pigeons apparently began nesting later than and were about one-third as productive as adults. In Oregon, most of the adult population could fledge as many as two young over the 100-110-day nesting period, resulting in a maximum potential recruitment of 47-50% juveniles. We estimated that the fall population contained about 23% juveniles, 12% yearlings, and 65% adults. Mean annual survival of adults was 63.7%, but was year-specific. To maintain a stable population with the estimated survival rates required production near the biotic potential (40.8%). Conversely, a stable population could be attained with the estimated rate of recruitment (23%) and high but realistic rates of survival (adults, 83%; juveniles, 68%). Counts of band-tailed pigeons at mineral sites in Oregon indicated that the population had undergone two periods of modest increase (2.4-7.1% per year) and two periods of sharp decline (10.4-11.1% per year). In 1988 the population index was only 34% of the 1950-88 average. Harvest of band-tailed pigeons in the three Pacific Coast states averaged 414,000 from 1957 to 1983; about 55% of the harvest took place in California, 23% in Washington, and 22% in Oregon. In Oregon, about 65% of the harvest took place in the first 10 days of September and 40% was at mineral sites. Fewer juveniles were shot at mineral sites (13%) than at feeding areas (25%). Hunting at mineral sites was directed at experienced breeders and may be particularly detrimental to the population. However, the overall effect of hunting on abundance was not determined. Band-tailed pigeons fed extensively on elder ( Sambucus spp.) and cascara buckthorn ( Rhamnus purshiana ) berries while nesting. The emergence of Pacific red elder (S. callicarpa) berries in June provided the food resources necessary for initiation of reproduction in Oregon, and probably throughout the Northwest. Elder berries contain little calcium (0.06-0.12%), therefore, the pigeons in the Northwest may require a mineral supplement in their diet. Mineral sites may be the scarcest resource required for reproduction by band-tailed pigeons in the Northwest.

Oregon↗
USGS1991

Standing crops and ecology of aquatic invertebrates in agricultural drainwater ponds in California

We examined standing crops and ecology of aquatic invertebrates in agricultural drainwater evaporation ponds in California from October 1982 to March 1983 and September 1983 to March 1984. Evaporation ponds supported low diversities but high standing crops of aquatic invertebrates. A water boatman ( Trichocorixa reticulata ) and a midge ( Tanypus grodhausi ) were the most abundant invertebrates, constituting 44.9% and 51.4% of total macroinvertebrate biomass. Regression models indicated that of 6 environmental variables measured, only electrical conductivity (EC) and Julian date affected biomass and density of water boatmen. EC was the only significant correlate of midge biomass in evaporation ponds.

California↗
USGS1991

Feeding ecology of waterfowl wintering on evaporation ponds in California

We examined the feeding ecology of Northern Pintails (Anas acuta), Northern Shovelers (A. clypeata), and Ruddy Ducks (Oxyura jamaicensis) wintering on drainwater evaporation ponds in California from 1982 through 1984. Pintails primarily consumed midges (Chironomidae) (39.3%) and widegeongrass (Ruppia maritima) nutlets (34.6%). Shovelers and Ruddy Ducks consumed 92.5% and 90.1% animal matter, respectively. Water boatmen (Corixidae) (51.6%), rotifers (Rotatoria) (20.4%), and copepods (Copepoda) (15.2%) were the most important Shoveler foods, and midges (49.7%) and water boatmen (36.0%) were the most important foods of Ruddy Ducks. All three species were opportunistic foragers, shifting their diets seasonally to the most abundant foods given their behavioral and morphological attributes.

Condor↗