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599 records · Page 34Linked to original sources
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↗