Autumnal migration of Eared Grebes ( Podiceps nigricollis ) through southwestern Wyoming: a key to assessing the size of the North American population

In autumn the vast majority of the North American population of Eared Grebes ( Podiceps nigricollis ) congregates for several months at Great Salt Lake, Utah, and Mono Lake, California. Because the lakes are so large, it has not been possible to monitor grebe migration with sufficient accuracy to determine when peak numbers are reached. To clarify migration phenology, we analyzed data from 2 isolated wetland areas in southwestern Wyoming where grebes land en route between breeding areas in the interior and Great Salt Lake. Occasional birds, probably nonbreeders or failed breeders, begin moving southward as early as mid-June. Migration of postbreeding birds starts in late July, peaks in late August and September, and is largely completed by the end of October, with very small numbers arriving into November. The pattern of migration and number of birds encountered varied annually, but 95% of the migration was usually completed by 15 October. As a result, censuses at the major staging lake made on or after 15 October but before the grebes depart for wintering areas can be used to study trends in size of the North American population.     

Terrestrial vertebrates of the Mono Lake islands, California

We compared vertebrate populations between the two major islands (paoha and Negit) in Mono Lake, California and the adjacent mainland to further elucidate the mechanisms underlying island colonization. Deer mice ( Peromyscus maniculatus ) and montane voles ( Microtus montanus ) were captured on Paoha, but only deer mice were captured on Negit. In contrast, eight species of rodents were captured on the mainland. Overall rodent abundance on Paoha and the mainland was similar, but on Negit it was about three times greater than on Paoha or the mainland. Adult deer mice from Paoha were significantly ( P Canis latrans ) and one or two species of lagomorphs were observed on the islands and the mainland. No amphibians or reptiles were found on the islands; both occurred in low numbers on the mainland. Rafting and human transport are probable means of colonization for mice and voles. The occurrence of coyotes on the islands may have modified historic predator-prey relationships, and thus the population of rodents and lagomorphs.     

Detection of doubled shot noise in short normal-metal/superconductor junctions

Shot noise refers to the fluctuations in electrical current through a device arising from the discrete nature of the charge-carrying particles. Recent experiments have exploited the fact that the shot noise is proportional to the charge of the carriers to establish fractional quantization of quasiparticles in the fractional quantum Hall effect. By a similar argument, it is expected that when a superconducting reservoir emits Cooper pairs, (which have a charge twice that of an electron) into a short normal-metal wire, the shot noise should be double that obtained for a normal-metal reservoir. Although the charge of Cooper pairs has been well established by flux quantization and tunnel experiments, doubling of their shot noise has not yet been observed. Here we report a shot-noise experiment using a short diffusive normal-metal superconductor contact, in which we confirm the predicted noise behaviour for double charges. The measurements, taken over a large range of bias current, establish that phase coherence is not required to observe the effect.     

Biology of Red-necked Phalaropes ( Phalaropus lobatus ) at the western edge of the Great Basin in fall migration

Large numbers of Red-necked Phalaropes migrate overland across the Great Basin in fall, occurring commonly at highly saline lakes. Migrants occur at Mono Lake, California, from mid-July to mid-October. The earliest migrants are adult females, followed several weeks later by adult males, and finally by juveniles. Adults make up ca 75% of the population, with males outnumbering females by 5:4. From 1980 through 1984 an estimated 52,000–65,000 birds passed through the area each year, except in 1983, when only 36,000 were recorded. The low number might be attributable to high mortality on oceanic wintering grounds in the Southern Hemisphere in 1982 associated with the severe El Ni&#241o. At Mono Lake the phalaropes concentrate near the shore and feed almost exclusively on brine flies. The migrants neither gain much weight nor accomplish much molt during their sojourn, which suggests that the average stay is only a few days. Some aspects of the molt pattern differ from those reported elsewhere.