Geology topics

Robert L. Jarvis

Publications and source records attributed to Robert L. Jarvis.

7 recordsLinked to original sources

USGS2005

Do wintering Harlequin Ducks forage nocturnally at high latitudes?

We monitored radio-tagged Harlequin Ducks ( Histrionicus histrionicus ) to determine whether nocturnal feeding was part of their foraging strategy during winter in south-central Alaska. Despite attributes of our study site (low ambient temperatures, harsh weather, short day length) and study species (small body size, high daytime foraging rates) that would be expected to favor nocturnal foraging, we found no evidence of nocturnal dive-feeding. Signals from eight radio-tagged Harlequin Ducks never exhibited signal loss due to diving during a total of 780 minutes of nocturnal monitoring. In contrast, the same eight birds exhibited signal loss during 62 ± 7% (SE) of 5-minute diurnal monitoring periods (total of 365 minutes of monitoring). Our results suggest that Harlequin Ducks in south-central Alaska face a stringent time constraint on daytime foraging during midwinter. Harlequin Ducks wintering at high latitudes, therefore, may be particularly sensitive to factors that increase foraging requirements or decrease foraging efficiency.

Condor↗

USGS2005

Evaluation of current population indices for band-tailed pigeons

There is no formal population survey specifically designed to index population abundance of band-tailed pigeons ( Patagioenas fasciata ) throughout their range. Data from the Breeding Bird Survey (BBS), Washington and Oregon Mineral-Site (WAORMS) surveys, and Washington Call Count (WACC) survey offer evidence of long-term population decline. We investigated the potential to augment BBS, WACC, and WAORMS surveys to provide more precise population indices for the Pacific Coast band-tailed pigeon ( P. f. monilis ) and augment the BBS to index the Interior or “Four Corners” population ( P. f. fasciata ). We calculated statistical power, the probability of detecting population change given that a change exists, and analyzed survey data to investigate the effect of route length, survey repetition, and sample size. Sample sizes of 50 sites or routes yielded corresponding powers of 99% for WAORMS, 54% for WACC, and 30% for Pacific BBS, to detect a 10% annual change over a 5-year period (a = 0.10). Route length and repetition of surveys had little impact on power. Mineral-site surveys provide the greatest potential to monitor breeding populations and detect short-term trends in the Pacific Coast population. New survey techniques are needed for the Interior band-tailed pigeon.

Wildlife Society Bulletin↗

USGS2004

Habitat selection by female northern pintails wintering in the Grassland Ecological Area, California

To determine relative importance of habitats available in the Grassland Ecological Area (GEA) to wintering female northern pintails, Anas acuta, we studied habitat use relative to availability (i.e., habitat selection) in the GEA during September through March, 1991-94 for 196 Hatch-Year (HY) and 221 After-Hatch-Year (AHY) female pintails that were radio tagged during August-early October in the GEA (n = 239), other San Joaquin Valley areas (n = 132), or other Central Valley areas (n = 46). Habitat availability and use varied among seasons and years, but pintails always selected shallow and, except on hunting days, open habitats. Swamp timothy, Heleochloa schoenoides, marsh was the most available, used, and selected habitat. Watergrass, Echinochloa crusgalli, marsh in the GEA was used less than available at night in contrast to previous studies in other SJV areas. Preferred late-winter habitats were apparently lacking in the GEA, at least relative to in the Sacramento Valley and Delta where most pintails moved to in December each year. Impacts on pintails of the increasing practice of managing marshes for increased emergent vegetation to attract other species should be monitored. Shallow, open habitats that produce seeds and invertebrates available to pintails in late winter would help maintain pintail abundance in the GEA.

California Fish and Game↗

USGS2003

Selection of flooded agricultural fields and other landscapes by female northern pintails wintering in Tulare Basin, California

Habitat selection and use are measures of relative importance of habitats to wildlife and necessary information for effective wildlife conservation. To measure the relative importance of flooded agricultural fields and other landscapes to northern pintails ( Anas acuta ) wintering in Tulare Basin (TB), California, we radiotagged female pintails during late August-early October, 1991-1993 in TB and other San Joaquin Valley areas and determined use and selection of these TB landscapes through March each year. Availability of landscape and field types in TB changed within and among years. Pintail use and selection (based upon use-to-availability log ratios) of landscape and field types differed among seasons, years, and diel periods. Fields flooded after harvest and before planting (i.e., pre-irrigated) were the most available, used, and selected landscape type before the hunting season (Prehunt). Safflower was the most available, used, and-except in 1993, when pre-irrigated fallow was available-selected pre-irrigated field type during Prehunt. Pre-irrigated barley-wheat received 19-22% of use before hunting season, but selection varied greatly among years and diel periods. During and after hunting season, managed marsh was the most available, used, and, along with floodwater areas, selected landscape type; pre-irrigated cotton and alfalfa were the least selected field types and accounted for <13% of pintail use. Agricultural drainwater evaporation ponds, sewage treatment ponds, and reservoirs accounted for 42-48% of flooded landscape available but were little used and least selected. Exodus of pintails from TB coincided with drying of pre-irrigated fallow, safflower, and barley-wheat fields early in winter, indicating that preferred habitats were lacking in TB during late winter. Agriculture conservation programs could improve TB for pintails by increasing flooding of fallow and harvested safflower and grain fields. Conservation of remaining wetlands should concentrate on increasing the amount and productivity of marsh that is shallow-flooded as pre-irrigated grain fields dry. If pin- tails were provided with adequate preferred field and marsh habitats, including hunt-day sanctuaries, contaminant risks associated with exposure to drainwater evaporation ponds probably should remain low for these waterfowl even if their abundance in TB increased.

California↗

USGS2002

Distribution and movements of female northern pintails radiotagged in San Joaquin Valley, California

To improve understanding of northern pintail (Anas acuta) distribution in central California (CCA), we radiotagged 191 Hatch-Year (HY) and 228 After-Hatch-Year (AHY) female northern pintails during late August-early October, 1991-1993, in the San Joaquin Valley (SJV) and studied their movements through March each year. Nearly all (94.3%) wintered in CCA, but 5.7% went to southern California, Mexico, or unknown areas; all that went south left before hunting season. Of the 395 radiotagged pintails that wintered in CCA, 83% flew from the SJV north to other CCA areas (i.e., Sacramento Valley [SACV], Sacramento-San Joaquin River Delta [Delta], Suisun Marsh, San Francisco Bay) during September-January; most went during December. Movements coincid- ed with start of hunting seasons and were related to pintail age, mass, capture location, study year, and weather. Among pintails with less than average mass, AHY individuals tended to leave the SJV earlier than HY individuals. Weekly distribution was similar among capture locations and years but a greater percentage of pintails radiotagged in Tulare Basin (south part of SJV) were known to have (10.3% vs. 0.9%) or probably (13.8% vs. 4.6%) wintered south of CCA than pintails radiotagged in northern SJV areas (i.e., Grassland Ecological Area [EA] and Mendota Wildlife Area [WA]). Also, a greater percentage of SJV pintails went to other CCA areas before hunting season in the drought year of 1991-1992 than later years (10% vs. 3-5%). The percent of radiotagged pintails from Grass- land EA known to have gone south of CCA also was greater during 1991-1992 than later years (2% vs. 0%), but both the known (19% vs. 4%) and probable (23% vs. 12%) percent from Tulare Basin that went south was greatest during 1993-1994, when availability of flooded fields there was lowest. The probability of pintails leaving the SJV was 57% (95% CI = 8-127%) greater on days with than without rain, and more movements per bird out of SJV occurred in years with more rain and fog but fewer days with southerly winds. Movements by pintails and changes in pintail distributions, direct recovery distributions, and harvest rates suggest the disproportionate decline of pin- tails in Tulare Basin was due to a lower percentage of pintails moving there in fall and a greater percentage or ear- lier movements north and south out of Tulare Basin. With fewer in Tulare Basin to replace Grasslands EA pintails going north in December, pintail abundance in the northern SJV declined during late winter. Changes in move- ment patterns correspond to habitat loss in Tulare Basin and increased habitats in SACV and western mainland Mexico. Habitat improvements, especially in Tulare Basin, that increase food, sanctuary, and winter survival would probably help restore pintails throughout the SJV.

Journal of Wildlife Management↗

USGS2000

Testing assumptions for unbiased estimation of survival of radiomarked harlequin ducks

Unbiased estimates of survival based on individuals outfitted with radiotransmitters require meeting the assumptions that radios do not affect survival, and animals for which the radio signal is lost have the same survival probability as those for which fate is known. In most survival studies, researchers have made these assumptions without testing their validity. We tested these assumptions by comparing interannual recapture rates (and, by inference, survival) between radioed and unradioed adult female harlequin ducks ( Histrionicus histrionicus ), and for radioed females, between right-censored birds (i.e., those for which the radio signal was lost during the telemetry monitoring period) and birds with known fates. We found that recapture rates of birds equipped with implanted radiotransmitters (21.6 ± 3.0%; x̄ ± SE) were similar to unradioed birds (21.7 ± 8.6%), suggesting that radios did not affect survival. Recapture rates also were similar between right-censored (20.6 ± 5.1%) and known-fate individuals (22.1 ± 3.8%), suggesting that missing birds were not subject to differential mortality. We also determined that capture and handling resulted in short-term loss of body mass for both radioed and unradioed females and that this effect was more pronounced for radioed birds (the difference between groups was 15.4 ± 7.1 g). However, no difference existed in body mass after recapture 1 year later. Our study suggests that implanted radios are an unbiased method for estimating survival of harlequin ducks and likely other species under similar circumstances.

Alaska↗

USGS1994

Survival of radio-marked mallard ducklings in northeastern California

Estimates of duckling survival are necessary to accurately assess recruitment of mallards ( Anas platyrhynchos ), yet few reliable estimates exist. During 1988-90, we estimated survival rates for 127 radio-marked mallard ducklings from 64 broods on Lower Klamath National Wildlife Refuge, California. In 1988, we restricted the survival estimate to the first 10 days post-hatch ( S = 0.18, SE = 0.07). Survival from hatching to 50 days was 0.37 (SE = 0.09) in 1989 and 0.34 (SE = 0.07) in 1990. Total brood loss differed among years ( P < 0.05); 81.2% in 1988 ( n = 16), 36.8% in 1989 ( n = 19), and 37.5% in 1990 ( n = 24). Ninety-three percent of mortality occurred during the first 10 days of life. We detected no differences in the proportion of radio-marked ducklings fledged from early-hatched versus late-hatched nests ( P = 0.74). During 1989-90, 16 females appeared to lose their entire brood; however, 3 radio-marked ducklings from 2 of these broods were fledged by other brood hens. Of 29 radio-marked ducklings that reached 44 days of life, 6 (20.7%) joined other broods. Habitat enhancement is the key to improving duckling survival because the large number of predator species that consume ducklings makes predator control difficult.

California↗