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Geology topics

John Y. Takekawa

Publications and source records attributed to John Y. Takekawa.

At least 235 records · Page 13Linked to original sources
USGS2004

Effects of radiotransmitters on the reproductive performance of Cassin's auklets

We examined whether radiotransmitters adversely affected the reproductive performance of Cassin's auklets ( Ptychoramphus aleuticus ) breeding on the California Channel Islands during 1999-2001. We attached external radiotransmitters to 1 partner in 108 Cassin's auklet pairs after nest initiation and used 131 unmarked, but handled, pairs as controls. Compared to alpha chicks raised by radiomarked pairs, alpha chicks raised by unmarked pairs had faster mass growth rates (1.95 ± 0.30 g d −1 vs. 3.37 ± 0.53 g d −1 , respectively), faster wing growth rates (2.46 ± 0.10 mm d −1 vs. 2.85 ± 0.05 mm d −1 ), greater peak fledging masses (118.9 ± 3.5 g vs. 148.3 ± 2.4 g), and higher fledging success (61% vs. 90%). Fledging success was reduced more when we radiomarked the male (50% fledged) rather than the female partner (77% fledged). After fledging an alpha chick, unmarked pairs were more likely to initiate a second clutch (radiomarked: 7%; unmarked: 39%) but did not hatch a second egg (radiomarked: 4%; unmarked: 25%) or fledge a second (beta) chick (radiomarked: 4%; unmarked: 18%) significantly more often than radiomarked pairs. We resighted 12 radiomarked individuals nesting during a subsequent breeding season; each bird had shed its transmitter and healed the site of attachment. We suggest caution in using telemetry to evaluate the reproductive performance of alcids, but marking only females may minimize adverse effects.

California↗
USGS2004

Differential spring migration by male and female Western Sandpipers at interior and coastal stopover sites

Western Sandpipers Calidris mauri are differential migrants on their non-breeding areas, with females wintering farther south. Earlier passage of males in the spring has been explained by sexual differences in winter latitude (male-biased sex ratios at more northerly areas) and onset of migration (males departing earlier). We investigated sex differences during spring migration by capturing and radio-marking Western Sandpipers at two Pacific coast sites, San Francisco Bay, California and Grays Harbor, Washington and at a Great Basin interior wetland, Honey Lake, California. We monitored northward migration of 132 radio-marked birds at a network of 12 major stopover sites and 4 breeding areas. At the banding sites, we observed differences in sex by date and site, with males preceding females. We found sex differences in departure time of radio-marked birds from the banding site. their arrival time at the Copper River Delta, Alaska (our most frequently used stopover site), and in the likelihood that a stopover was used. Our data suggest that by mid to late April, migration timing becomes more compressed and sex differences are less pronounced and harder to detect.

Ardea↗
USGS2003

Long term productivity of canvasbacks ( Aythya valisineria ) in a snowpack-driven desert marsh

Ruby Lake, Nevada, is a large palustrine wetland that hosts the southern-most major breeding population of Canvasbacks ( Aythya valisineria ). That arid marsh, fed by springs derived from mountain snowpack, differs in climate and hydrology from glaciated potholes of the northern prairies where most Canvasbacks breed. Fourteen years of nesting data on Canvasbacks over a 31 year period (1970–2000) were analyzed to determine factors affecting breeding performance at Ruby Lake and whether they differed from those in the prairies. Long-term Mayfield nest success at Ruby Lake (50% of all nests) was in the range of that in the northern prairies (21–65%). Of all Canvasback nests, 73% were parasitized (mostly by Redheads [ Aythya americana ]) as compared to 83–97% in a large Manitoba marsh and 57–65% in Manitoba potholes. However, as in the northern prairies, nest parasitism generally had little or no effect on either nest success or percentage of host eggs that hatched. In Manitoba potholes, nest success was unrelated to habitat variables measured; but successful nests at Ruby Lake were over shallower water, farther from shore, in wider bands of emergent vegetation, and surrounded by lower stem densities than unsuccessful nests. Water level is the key factor in breeding performance of Canvasbacks at both Ruby Lake and the northern prairies; however, the source of water differs (mountain snowpack at Ruby Lake, direct precipitation in the prairies) and effects of water-level variations are reversed. In small prairie potholes (mostly <0.4 ha) with many mammalian predators, productivity of Canvasbacks (which build floating nests) is increased by high water that floods the emergent fringe. At Ruby Lake, a very large marsh (2,830 ha) with mostly avian predators, Canvasback productivity is decreased by high water that floods interior emergent stands too deeply. Water level at Ruby Lake was highly correlated (multiple R 2 = 0.91) with mountain snowpack up to three years earlier, emphasizing the strong effect of climatic variations on wetland birds in that arid region.

The Auk↗
USGS2003

Winter distribution and survival of a high-desert breeding population of canvasbacks

The southernmost major breeding area of Canvasbacks ( Aythya valisineria ) is located at the Ruby Lake National Wildlife Refuge, Nevada, in the high desert of the western Great Basin. We determined winter distributions, recovery rates, and survival for Canvasbacks banded in Nevada from March to November, 1968–2000. Winter recovery distributions did not differ by sex or age, but differed between direct recoveries (same year as banding) and indirect recoveries (after year of banding), indicating variable site use between years. Of direct band returns (October–March), 92% were from the Pacific Flyway and 56% were from California alone. In California, recovery distributions shifted from southern California and the San Francisco Bay estuary in the 1970s to the Central Valley in the 1980s and 1990s. In the 1990s, there were no recoveries in San Francisco Bay, historically the major wintering area for Canvasbacks in the Pacific Flyway. Adult and juvenile survival decreased by 24% between the 1980s and 1990s. Ruby Lake Canvasbacks exhibited weaker fidelity to wintering sites than Canvasbacks wintering on the Atlantic and Gulf coasts. Moreover, no major concentrations occurred during fall migration, unlike patterns in eastern North America. Shifts in distribution and survival may correspond to effects of El Niño weather on habitat conditions in Nevada and San Francisco Bay, and to major improvements in water delivery and wetland restoration in the Central Valley. Canvasbacks that use widely distributed and variable habitats may be good indicators of the effects of changing climate and water-use practices on waterbirds throughout this arid region.

Condor↗
USGS2003

Science support for managing migratory waterfowl.

Migratory birds in North America are an international resource shared by Canada, the United States, and Mexico. Ultimate population management authority in the U.S. lies with the U.S. Fish and Wildlife Service (FWS), but states participate in development of management decisions through the Flyway system. The FWS, state wildlife agencies, and nongovernmental organizations participate through independent actions and cooperative Joint Ventures under the North American Waterfowl Management Plan (NAWMP) to acquire, protect, restore, and enhance wetlands and other habitats critical to the long-term conservation of breeding, migrating, and wintering waterfowl. A thorough base of scientific information is required to support and evaluate waterfowl populations and habitat management in North America.

WERC Fact Sheet↗
USGS2003

Satellite telemetry and wildlife studies in India: Advantages, options and challenges

Greater spatial coverage, accuracy and non-invasiveness of satellite technology make it one of the best tools to track long-distance migrants, which is otherwise difficult using conventional radio telemetry. In this article, we review the evolution of satellite telemetry and its application. We provide examples of three recent studies in India that have demonstrated and created a widespread appreciation of the use and benefits of satellite telemetry among biologists and managers. We also discuss the future prospects of this technology vis-a-vis benefits and challenges in the Indian subcontinent.

Current Science↗
USGS2002

Relating body condition to inorganic contaminant concentrations of diving ducks wintering in coastal California

One egg from each of 114 red-breasted merganser (Mergus serrator) nests in 1977 and 92 nests in 1978 was collected and later analyzed for organochlorines, polybrominated biphenyls (PBBs), polychlorinated styrenes (PCSs). and metals. One egg was also collected from each of the dabbling duck nests located: Twenty-nine of these eggs were analyzed for organochlorines and metals in 1977; 10 eggs were analyzed in 1978. All merganser eggs contained DDE, polychlorinated biphenyls (PCBs), and dieldrin; all but one egg collected in 1978 contained DDT. DDE and PCB levels had declined since 1975 to a geometric mean of 7.4 ppm DDE and 20 ppm PCBs in 1977 and 7.6 ppm DDE and 19 ppm PCBs in 1978. Dieldrin residues in eggs had not declined from 1975 Ievels; the geometric mean was 0.78 ppm in 1977 and 0.76 ppm in 1978. Other organochlorines were present at low levels. Mercury residues averaged >0,50 ppm in merganser eggs and had not declined since 1975. Other metals were present at low levels. Dabbling ducks generally had much lower organochlorine and Hg residues than mergansers; DDE and PCBs were the only organochlorines present in the majority of eggs. Geometric means of PCBs and DDE in dabbling duck eggs did not exceed 2.0 ppm and 1.0 ppm, respectively. PBBs and PCSs were detected only in a few merganser eggs, at low levels. Eggshell thickness for red-breasted merganser eggs averaged 0.359 mm in 1977 and 0.355 mm in 1978, which is only 2%-3% below pre-1946 thicknesses. Mallard (Anas platyrhynchos) eggshell thicknesses averaged 0.331 mm in 1977 and 0.337 mm in 1978.

Archives of Environmental Contamination and Toxico↗
USGS2002

Western Sandpipers ( Calidris mauri ) during the non-breeding season: Spatial segregation on a hemispheric scale

The nonbreeding distribution of Western Sandpipers ( Calidris mauri ) was documented using 19 data sets from 13 sites along the Pacific and Atlantic coasts of the Americas. Western Sandpipers showed latitudinal segregation with regard to sex and age. Females wintered farther south than males. A “U” shaped pattern was found with respect to age, with juveniles occurring at higher proportions at both the northern and southern ends of the range. Distribution of sexes might be affected by differences in bill length and a latitudinal trend in depth distribution of prey. For age class distribution, two different life-history tactics of juveniles might exist that are related to the higher cost of feather wear for juveniles compared to adults. Most juveniles complete three long-distance migrations on one set of flight feathers whereas adults complete two. Juveniles may winter either far north, thereby reducing feather wear induced by ultraviolet light, migration, or both, or far south and spend the summer on the nonbreeding area.

The Auk↗
USGS2002

Clam density and scaup feeding behavior in San Pablo Bay, California

San Pablo Bay, in northern San Francisco Bay, California, is an important wintering area for Greater ( Aythya marila ) and Lesser Scaup ( A. affinis ). We investigated variation in foraging behavior of scaup among five sites in San Pablo Bay, and whether such variation was related to densities of their main potential prey, the clams Potamocorbula amurensis and Macoma balthica . Time-activity budgets showed that scaup spent most of their time sleeping at some sites, and both sleeping and feeding at other sites, with females feeding more than males. In the first half of the observation period (12 January–5 February 2000), percent time spent feeding increased with increasing density of P. amurensis , but decreased with increasing density of M. balthica (diet studies have shown that scaup ate mostly P. amurensis and little or no M. balthica ). Densities of M. balthica stayed about the same between fall and spring benthic samples, while densities of P. amurensis declined dramatically at most sites. In the second half of the observation period (7 February–3 March 2000), percent time feeding was no longer strongly related to P. amurensis densities, and dive durations increased by 14%. These changes probably reflected declines of P. amurensis , perhaps as affected by scaup predation. The large area of potential feeding habitat, and alternative prey elsewhere in the estuary, might have resulted in the low correlations between scaup behavior and prey densities in San Pablo Bay. These low correlations made it difficult to identify specific areas of prey concentrations important to scaup.

Condor↗
USGS2002

Waterbird use of bayland wetlands in the San Francisco Bay estuary: Movements of long-billed dowitchers during the winter

The San Francisco Bay estuary is a migration and wintering area for more than 1.5 million waterbirds on the west coast of North America. Because the estuary is located in a metropolitan area, development and diking of baylands (the region between the edge of the bay and the historical high tide line) have greatly altered the wetland landscape. Recently, conservation interests have promoted restoration of diked baylands to tidal salt marshes for the benefit of endangered native species. However, effects of tidal marsh conversion on the existing community of waterbirds in the baylands are largely unknown, especially in muted tidal marshes with restricted inflows and in artificial salt evaporation ponds where high waterbird densities are found. The first radio-marking study of the Long-billed Dowitcher ( Limnodromus scolopaceus ) was conducted in November-December 2000 to examine their use of baylands. We captured 32 birds by rocket netting in a muted tidal marsh on the North Bay and radio-marked them with 1.2 g transmitters affixed with glue. Individuals were tracked for an average of 20.3 d (±8.5 SD) and obtained 217 high tide and 195 low tide locations. Movements between tides (x̄ = 1.29±1.48 SD km) and home range sizes (x̄ = 17.7±16.0 SD km 2 ) were highly variable. Long-billed Dowitchers preferred open habitats such as muted tidal marshes during the high tide, but the majority (78.5%) also remained in these wetlands during low tide rather than feeding at nearby mud flats. Their avoidance of mud flats contrasted sharply with Western Sandpipers ( Calidris mauri ) but was similar to Black-necked Stilts ( Himantopus mexicanus ). Seven Long-billed Dowitchers flew 110 km inland to Central Valley wetlands in mid-December, a regional movement documented earlier for Dunlin ( Calidris alpina ) wintering on the coast. However, unlike Dunlin, their movements were not in response to rainfall but may have been in response to a low pressure front or possibly predictable flooding of fields in the Central Valley. Although the estuary is a major wintering area supporting large numbers of waterbirds, some birds such as Long-billed Dowitchers move inland to freshwater wetlands in the Central Valley.

Waterbirds↗
USGS2002

Management and conservation of San Francisco Bay salt ponds: effects of pond salinity, area, tide, and season on Pacific Flyway waterbirds

Throughout the world, coastal salt ponds provide habitat for large numbers and diversities of water- birds. San Francisco Bay contains the most important coastal salt pond complexes for waterbirds in the United States, supporting more than a million waterbirds through the year. As an initial step in attempting to understand how the anticipated conversion of salt ponds to tidal marsh might affect the Bay's bird populations, the number of birds using salt ponds on high and low tides was counted during the winter months of 1999/00 and 2000/01. Be- havior and habitat use of birds in these ponds were assessed, and the effects of tide cycle, pond salinity, and pond area on bird use were examined. We recorded 75 species ofwaterbirds in surveys of salt ponds in the South Bay from September 1999 to February 2001, totaling over a million bird use days on high tide. Shorebirds and dabbling ducks were the most abundant groups of birds using the salt ponds. Waterbird numbers and diversity were significantly affected by the salinity of ponds in a non-linear fashion with lower numbers and diversity on the highest salinity ponds. With the exception of ducks and Eared Grebe (Podiceps nigricollis), tide height at the Bay significantly affect- ed bird numbers in the salt ponds with ponds at high tides having higher numbers of birds than the same ponds on low tides. Considerable numbers of birds fed in the salt ponds on high and low tides, although this varied greatly by species. Habitat use varied by tide. Management recommendations include maintaining ponds of varying salini- ties and depths. Restoring salt ponds to tidal marsh should proceed with caution to avoid loss of waterbird diversity and numbers in San Francisco Bay.

Waterbirds↗
USGS2002

Transportation impacts to wildlife on state route 37 in northern San Pablo Bay, California

State Route 37 bisects conservation lands managed by San Pablo Bay National Wildlife Refuge (U.S. Fish & Wildlife Service) and Napa-Sonoma Marshes Wildlife Area (California Department of Fish and Game) in Solano and Sonoma Counties. The 2-lane highway connects Interstates 101 and 80 in northern San Francisco Bay and experiences ~26,000 vehicles per day. Road-killed wildlife between Napa River and Tolay Creek bridges (14.7 km) were counted in 2000 to ascertain species composition, relative abundance, and relative occurrence (animal fatality interval). The primary objectives of the study were to determine if endangered salt marsh harvest mice (Reithrodontomys raviventris), California clapper rails (Rallus longirostris), or other species of concern were represented, and to collect baseline data on transportation impacts to wildlife in the area. During 51 surveys, 291 dead birds (54.6%) and mammals (45.4%) were observed. Endangered species were not positively identified dead on the highway. In total, 28 bird, 10 mammal and 1 reptile species were positively identified along this section of highway that traverses tidal marsh and diked baylands (i.e., salt ponds, seasonal wetlands, and oat-hay agriculture fields). The mean animal fatality interval for both lanes was one road-kill every 2.1km (2.1 km SD).

Transactions of the Western Section of the Wildlif↗