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659 records · Page 37Linked to original sources
USGS1999

Seasonal movements, migration, and range sizes of subadult and adult Bamforth Lake California Gulls

We investigated seasonal migration patterns of three age classes of California Gulls (Larus californicus). Using band recovery data and reported sightings of patagially marked gulls, we constructed location maps for fledglings, one to two-year-old gulls, and breeding-age adult gulls during five time periods: spring migration, breeding season, early and late fall migration, and winter. Using repeated observations, we also produced a location map with directional vector plots. Gulls followed a triangular pattern of movements. At the conclusion of breeding, gulls migrated west and northwest to the Pacific coast, distributing themselves mainly between San Francisco and British Columbia. During winter, gulls moved south along the Pacific coast and by spring were concentrated in southern California and northern Mexico. The range size was largest among fledgings which provided the northernmost and southernmost observations for the population. Few subadult gulls migrated to the breeding colony. During the breeding season, a substantial portion of breeding-aged adults remained on the Pacific coast and throughout the intermountain west but were not observed at other California gull colonies. While fledgings moved directly toward the Pacific coast at the end of the breeding season, many adults lingered near the colony site at aquatic habitats south of the colony. We suggest that adults remain longer in the area to feed and to rejuvenate before attempting migration.

Waterbirds↗
USGS2000

Late summer survival of adult female and juvenile spectacled eiders on the Yukon-Kuskokwim Delta, Alaska

We used radio-telemetry to examine survival of adult female and juvenile Spectacled Eiders (Somateria fischeri) from 30 days after hatch until departure from the Yukon-Kuskokwim Delta (YKD) during 1997-1999. Juvenile survival was 71.4%; adult female survival was 88.5%. Mink (Mustella vison) were the most common predator identified for both adults and juveniles. Detectable levels of lead were found in bones of 74% of juvenile carcasses recovered and 21% had levels indicative of acute exposure. Average age at departure was 59 ?? 1 days old for juveniles and 56 ?? 1 days after hatch for adults. Most broods (60.5%) departed the YKD synchronously. Overall our data indicate that mortality during the latter half of brood-rearing is higher than previously thought. We conclude that brood rearing is a period of high mortality for brood-rearing females and that lead poisoning is responsible for reductions in juvenile survival to fledging. Received 15 February 2000, accepted 1 April 2000.

Waterbirds↗
USGS2000

Performance of implantable satellite transmitters in diving seabirds

We report on the first deployment of satellite transmitters in large alcids. In 1995 and 1996, we surgically implanted 51 transmitters in Common and Thick-billed murres ( Uria aalge and U. lomvia ) and Tufted Puffins ( Fratercula cirrhata ) at three colonies in Alaska. These devices furnished more than 2,900 locations over succeeding months (eight months maximum transmitter life), some 30-40% of which had calculated errors of <1,000 m. We considered other data to be reliable if locations were repetitive within a short period of time. As measures of data collection efficiency, we calculated location indices (number of locations per hour of transmission) of 0.44 during the breeding season and 0.35 overall. Those values compared favorably with satellite transmitters previously deployed on large mammals at similar latitudes. Transmitters did not last as long as expected because lithium batteries tended to self-discharge when kept at the high internal temperature of a bird. Most importantly, we encountered high mortality of instrumented birds, especially in the interval from 11-20 days after release. Our results suggest that radio transmission itself somehow impaired normal feeding behavior or otherwise compromised the birds' health. Those two problems (battery life and bird mortality) will need to be solved before implantable devices can be applied effectively to the same or similar species in the future.

Alaska↗
USGS2000

Do male breeding displays function to attract mates or defend territories? The explanatory role of mate and site fidelity

Many shorebirds show elaborate breeding displays that include aerial flights and ground displays accompanied by song. The mate attraction hypothesis suggests that breeding displays function to attract mates and maintain pair bonds, whereas the territory defense hypothesis suggests breeding displays function in defining and defending nesting and feeding territories. We tested these hypotheses in the Western Sandpiper ( Calidris mauri ) by contrasting the duration and level of male breeding displays among pairs that differed in their mate and site fidelity. As predicted by the mate attraction hypothesis, males performed the highest number of song sequences during pair formation, and males paired with their mate of a prior year sang less than males paired to new mates. Further, sitefaithful males mated to a new but experienced mate displayed significantly more than remated males or males new to the area. This suggests a male's prior familiarity with an area and his neighbors does not lessen his display rate as was predicted under the territory defense hypothesis. Limited support for the territory defense hypothesis came from observations of males performing breeding displays with neighboring males along nest territory boundaries. This behavior was short-lived, however, as males abandoned nesting areas after pair-formation and used adjacent or disjointed feeding areas during egg-laying and incubation. Male aggression (i.e., aerial and ground chases), as opposed to breeding displays, appeared to be the principal means of maintaining territory boundaries. Indeed, the rate at which males chased other males remained fairly constant and high throughout the breeding season. Male chasing behavior may also serve as a paternity guard to protect against extra-pair copulations. Our study also found that a female's prior breeding experience in an area correlated with a reduced display rate by her mate, particularly if that mate was new to the area. This indicates female characteristics may not only drive nest initiation, as has been shown in other studies, but are important in determining the duration and extent of male display.

Alaska↗
USGS2001

Selection of habitats by Emperor Geese during brood rearing

Although forage quality strongly affects gosling growth and consequently juvenile survival, the relative use of different plant communities by brood rearing geese has been poorly studied. On the Yukon-Kuskokwim Delta, Alaska, population growth and juvenile recruitment of Emperor Geese (Chen canagica) are comparatively low, and it is unknown whether their selection of habitats during brood rearing differs from other goose species. Radio-telemetry was used to document the use of habitats by 56 families of Emperor Geese in a 70 km2 portion of the Yukon-Kuskokwim Delta during brood rearing in 1994-1996. When contrasted with available habitats (a set of six habitat classes), as estimated from 398 random sampling locations, Emperor Geese strongly selected Saline Ponds, Mudflat, and Ramenskii Meadow habitats and avoided Levee Meadow, Bog Meadow, and Sedge Meadow. These selected habitats were the most saline, comprised one-third of the study area, and 43% of all locations were in Ramenskii Meadow. I contrasted these Emperor Goose locations with habitats used by the composite goose community, as inferred from the presence of goose feces at random locations. The marked difference between groups in this comparison implied that Cackling Canada Geese (Branta canadensis minima) and Greater White-fronted Geese (Anser albifrons) collectively selected much different brood rearing habitats than Emperor Geese. Received 20 February 2001, accepted 18 April 2001.

Waterbirds↗
USGS2001

The importance of survey timing in monitoring breeding seabird numbers

We conducted weekly aerial surveys of islands along the central Maine coast from April-June of 1993-1997 and used aerial photographs to determine peak nest count dates for Double-crested Cormorants (Phalacrocorax auritus), Herring Gulls (Larus argentatus) and Great Black-Backed Gulls (Larus marinus). These data also were used to determine the potential effect of survey timing on the ability to detect long-term trends in the abundance of these species. The number of cormorant nests in the study area peaked in mid-June, while Great Black-backed and Herring gulls peaked in late May and early June, respectively. Peak nesting dates generally were consistent for each island across years, but varied by up to a month between islands during a given year. A 10-year monitoring program using annual surveys conducted between 23 May and 23 June, or biennial surveys conducted from 2-17 June, would have an 80% probability of detecting annual changes of ??5% for all three species in this region. Received 1 November 2000, accepted 4 December 2000.

Waterbirds↗
USGS2002

Accessible habitat for shorebirds: Factors influencing its availability and conservation implications

We examined the relationship between water levels and accessible habitat, and how accessible habitat influenced Dunlin (Calidris alpina) and Semipalmated Sandpiper (Calidris pusilla) numbers in managed wetlands at Pea Island (North Carolina) and Merritt Island (Florida) National Wildlife Refuges in 1998 and 1999. At Pea Island we experimentally manipulated water levels, which also allowed us to examine the effects of water level fluctuations on prey base. We examined these relationships because access to foraging habitat by shorebirds is positively related to the length of their tarsometatarsus, and in the southeastern United States, small calidrids are a numerically important component of the two million migrants using inland and managed wetlands. We confirmed the importance of shallow waters for Dunlin and Semipalmated Sandpiper-numbers increased with increasing availability of 0-4 cm habitat. At Merritt Island, Dunlin use was inversely related to variability in water depth of 0-4 cm. Minimizing the frequency and amplitude of water level fluctuations associated with single-capped culverts is necessary to improve habitat quality. After adjusting for accessibility, spring habitat requirements for Dunlin and Semipalmated Sandpiper at Pea Island were met under nearly all abundance scenarios. We identified water level targets that maximize accessible habitat at Pea Island. In contrast, winter habitat requirements for Dunlin at Merritt Island were not met except in one scenario. Seasonally low prey density contributed to the shortfall, suggesting that allocating more habitat is the primary management option. Manipulating water levels at Pea Island did not adversely affect the density of eight shorebird prey species. Estimates of accessible habitat and other parameters (e.g., turnover rates, prey biomass) are essential to set and implement realistic shorebird habitat conservation goals.

Waterbirds↗
USGS2003

A voluntary program to curtail boat disturbance to waterfowl during migration

A voluntary waterfowl avoidance area (VWAA) was established on Lake Onalaska in Navigation Pool 7 of the Upper Mississippi River, Wisconsin, USA, in 1986, to reduce boating disturbance to migratory waterfowl. We monitored boater compliance with the VWAA program in 1993 and 1997. Of 1,664 "boating events" observed on Lake Onalaska, boats intruded into the VWAA on 127 occasions. Boating events have increased from 1.82 boating events/h in 1986-88 to 1.97 in 1993 and 2.58 in 1997. Despite a 60% increase in boating traffic, the lake-wide disturbance rates in 1997 were comparable to that in 1981. We attribute this to a significant reduction in the proportion of lake-wide boating events that resulted in disturbance, a direct consequence of the VWAA program. Rate of intrusion into the VWAA was 0.11 per boating event in 1997 compared to 0.18 per boating event in 1986-88. Boating disturbances to waterfowl within the VWAA occurred at about half the rate (0.24 to 0.28 disturbances ?? hr1) observed prior to establishment of the program (0.48 disturbances ?? hr1 . We also identified access points used by boaters and boating activities that were most likely to result in intrusion into the VWAA and associated disturbance to waterfowl. Results of these analyses have provided useful information to resource managers for targeting public education efforts. The VWAA program has contributed to the value of Lake Onalaska as a waterfowl refuge and demonstrates an effective collaboration among government agencies and non-governmental organizations.

Waterbirds↗
USGS2002

Development of an expert system for assessing trumpeter swan breeding habitat in the Northern Rocky Mountains.

A decision support system for the management of the Rocky Mountain Population of Trumpeter Swans (Cygnus buccinators) is being developed. As part of this, three expert systems are also in development: one for assessing the quality of Trumpeter Swan breeding habitat; one for making water level recommendations in montane, palustrine wetlands; and one for assessing the contribution a particular site can make towards meeting objectives from as flyway perspective. The focus of this paper is the development of the breeding habitat expert system, which currently consists of 157 rules. Out purpose is to provide decision support for issues that appear to be beyond the capability of a single persons to conceptualize and solve. We propose that by involving multiple experts in the development and use of the systems, management will be significantly improved. The knowledge base for the expert system has been developed using standard knowledge engineering techniques with a small team of ecological experts. Knowledge was then coded using production rules organized in decision trees using a commercial expert system development shell. The final system has been deployed on the world wide web.

Rocky Mountains↗
USGS2002

Bayesian time series analysis of segments of the Rocky Mountain trumpeter swan population

A Bayesian time series analysis technique, the dynamic linear model, was used to analyze counts of Trumpeter Swans (Cygnus buccinator) summering in Idaho, Montana, and Wyoming from 1931 to 2000. For the Yellowstone National Park segment of white birds (sub-adults and adults combined) the estimated probability of a positive growth rate is 0.01. The estimated probability of achieving the Subcommittee on Rocky Mountain Trumpeter Swans 2002 population goal of 40 white birds for the Yellowstone segment is less than 0.01. Outside of Yellowstone National Park, Wyoming white birds are estimated to have a 0.79 probability of a positive growth rate with a 0.05 probability of achieving the 2002 objective of 120 white birds. In the Centennial Valley in southwest Montana, results indicate a probability of 0.87 that the white bird population is growing at a positive rate with considerable uncertainty. The estimated probability of achieving the 2002 Centennial Valley objective of 160 white birds is 0.14 but under an alternative model falls to 0.04. The estimated probability that the Targhee National Forest segment of white birds has a positive growth rate is 0.03. In Idaho outside of the Targhee National Forest, white birds are estimated to have a 0.97 probability of a positive growth rate with a 0.18 probability of attaining the 2002 goal of 150 white birds.

Idaho, Montana, Wyoming↗
USGS2000

Foods, trophic relationships, and migration of Sooty and Short-tailed Shearwaters associated with squid and large-mesh driftnet fisheries in the North Pacific Ocean

We salvaged dead birds from high seas driftnets in the Central North Pacific Ocean during a study of the impact of high seas driftnet fishing on marine ecosystems. Digestive tract contents and stable isotopes of nitrogen and carbon in breast muscles of these birds were analyzed to assess the effect of driftnets on the trophic relationships of marine birds. The diets of Sooty ( Puffinus griseus ) and Short-tailed ( P. tenuirostris ) Shearwaters associated with high seas driftnets in the transitional region of the North Pacific Ocean overlap broadly. The principal differences between them include 1) Sooties prey more heavily on immature stages of invertebrates, especially the barnacle Lepas fascicularis than do Short-tails, 2) Pacific saury ( Cololabis saira ) are the primary fish taken by Sooties while lanternfish ( Myctophidae ) are the primary fish taken by Short-tails, and 3) Sooties take a wider variety of prey than do Short-tails. During the last years of extensive high seas driftnet fishing (early 1990's), both shearwaters augmented their diets with about 15% offal and discards from fishing vessels. Values for stable isotopes of nitrogen and carbon in breast muscle tissues (δ 15 N and δ 15 C) indicate the extent and timing of movements of Sooty Shearwaters: including arrival of migrants from the south Pacific (April-May), east to west movement from the eastern Pacific (May-June), and west to east movement from Japan (August-September). Fall migrant Sooties were not detected. The only movements of Short-tails that we detected were a few south-bound migrants in September-November.

Waterbirds↗