Criteria for Oil Spill Recovery: A Case Study of the Intertidal Community of Prince William Sound, Alaska, Following the Exxon Valdez Oil Spill

Marine intertidal organisms in Prince William Sound were exposed to crude oil following the T/V Exxon Valdez oil spill in 1989. The intertidal communities were also subjected to mechanical disturbance during invasive oil spill remediation and cleanup efforts. Using monitoring data collected from 1989 to 1997, impacts and eventual recovery were assessed at oiled but uncleaned sites and oiled and cleaned study areas. A statistical model where recovery was defined as parallelism between the time profiles at control and oiled sites was evaluated. Statistical analysis and graphical presentations of the data suggest intertidal epibiota communities recovered from the oil spill by 1992 at the oiled sites and by 1994 at the oiled and remediated sites. Empirical data from the intertidal monitoring program supports the use of tests of parallelism in evaluating recovery and the need to avoid simply the comparison of sample means from control and oiled sites.     

Managing Birds and Controlling Aircraft in the Kennedy Airport–Jamaica Bay Wildlife Refuge Complex: The Need for Hard Data and Soft Opinions

During the 1980s, the exponential growth of laughing gull (Larus atricilla) colonies, from 15 to about 7600 nests in 1990, in the Jamaica Bay Wildlife Refuge and a correlated increase in the bird-strike rate at nearby John F. Kennedy International Airport (New York City) led to a controversy between wildlife and airport managers over the elimination of the colonies. In this paper, we review data to evaluate if: (1) the colonies have increased the level of risk to the flying public; (2) on-colony population control would reduce the presence of gulls, and subsequently bird strikes, at the airport; and (3) all on-airport management alternatives have been adequately implemented. Since 1979, most (2987, 87%) of the 3444 bird strikes (number of aircraft struck) were actually bird carcasses found near runways (cause of death unknown but assumed to be bird strikes by definition). Of the 457 pilot-reported strikes (mean = 23 ± 6 aircraft/yr, N= 20 years), 78 (17%) involved laughing gulls. Since a gull-shooting program was initiated on airport property in 1991, over 50,000 adult laughing gulls have been killed and the number of reported bird strikes involving laughing gulls has declined from 6.9 ± 2.9 (1983–1990) to 2.6 ± 1.3 (1991–1998) aircraft/yr; nongull reported bird strikes, however, have more than doubled (6.4 ± 2.6, 1983–1990; 14.9 ± 5.1, 1991–1998). We found no evidence to indicate that on-colony management would yield a reduction of bird strikes at Kennedy Airport. Dietary and mark–recapture studies suggest that 60%–90% of the laughing gulls collected on-airport were either failed breeders and/or nonbreeding birds. We argue that the Jamaica Bay laughing gull colonies, the only ones in New York State, should not be managed at least until all on-airport management alternatives have been properly implemented and demonstrated to be ineffective at reducing bird strikes, including habitat alterations and increasing the capability of the bird control unit to eliminate bird flocks on-airport using nonlethal bird dispersal techniques. Because the gull-shooting program may be resulting in a nonsustainable regional population of laughing gulls (>30% decline), we also recommend that attempts be made to initiate an experimental colony elsewhere on Long Island to determine if colony relocation is a feasible management option.     

PATH CHOICE AND VISUAL STIMULI: SIGNS OF HUMAN ACTIVITY AND ARCHITECTURE

This paper is concerned with the exploratory behaviour of first-time visitors to an environment and specifically with the importance of visual stimuli in path choice. Forty-five participants were asked to select among photos representing the path choices at 13 street intersections in the historic centre of Montpellier, providing reasons as they proceeded. Preference among choices at intersections varied significantly in 10 of 13 cases. Eight intersections with the greatest differences in preference between choices were modified such that persons, signs, planters and awnings were removed from the most preferred scenes and inserted into the least preferred. The virtual tour was run again with a new group of participants. In comparison with the first group, the second expressed greater preference for path choices with added elements and diminished preference for photos with removed elements. Choices were also related to verbalizations and rated architectural properties.     

Estimation of Core Terrestrial Habitat for Stream-Breeding Salamanders and Delineation of Riparian Buffers for Protection of Biodiversity

Abstract:  Many species of wildlife depend on riparian habitats for various life-history functions (e.g., breeding, foraging, overwintering). Although this unique habitat is critical for many species, delineations of riparian zones and buffers for various taxa are lacking. Typically when buffer zones are determined to mitigate edge effects, they are based on criteria that protect aquatic resources alone and do not consider impacts to wildlife and other terrestrial resources. Using two different survey methods (area-constrained daytime searches and nighttime visual encounter searches), we estimated core terrestrial habitat and buffer widths for stream-breeding salamanders in southern Appalachian streams from May to August 2004. A core terrestrial habitat of 27.0 m encompassed 95% of the salamander assemblage (four species of stream plethodontids), and an additional 50 m (to buffer edge effects) yielded a total buffer of 77.0 m. When each species of the assemblage was analyzed separately, the maximum core terrestrial habitat needed for the Blue Ridge two-lined salamander ( Eurycea wilderae ), a dominant member and the farthest-ranging species from the stream, was 42.6 m. Thus, we recommend an overall buffer width of 92.6 m in southern Appalachian streams. To protect stream amphibians and other wildlife dependent on riparian areas, land managers and policy makers must consider conserving more than aquatic resources alone. Developing core terrestrial habitat estimates and buffer zone widths for wildlife populations is a critical first step in the conservation of many semiaquatic organisms and protecting biodiversity.     

Behavioral Assumptions of Conservation Policy: Conserving Oak Habitat on Family-Forest Land in the Willamette Valley, Oregon

Abstract:  Designing policies that harness the motivations of landowners is essential for conserving threatened habitats on private lands. Our goal was to understand how to apply ethnographic information about family-forest owners to the design of conservation policy for Oregon white oak (Quercus garryana) in the Willamette Valley, Oregon (U.S.A.). We examined owners' knowledge, beliefs, values, and socioeconomic contexts through in-depth individual and focus-group interviews to understand their motivations to conserve oak. We then used Schneider and Ingram's (1990) policy analysis framework to compare owners' motivations to the logic of policy. Owners had complex motivations for conserving oak. Despite this complexity, all 5 categories of policy that Schneider and Ingram describe hold promise. Policies that use symbolism to inspire behavior and policies that build capacity can harness owners' stewardship ethics and moral obligations. Policies that offer tangible rewards can build on owners' utilitarian motives. Policies that permit and prohibit behavior can tap owners' concerns about rule violations. Policies that promote voluntary, collaborative efforts can accommodate owners' need for autonomy and flexibility.     

Using Parasitic Trematode Larvae to Quantify an Elusive Vertebrate Host

Abstract: Digenean trematode parasites require multiple host species to complete their life cycles, and their abundance can often be strongly correlated with the abundance of their host species. Species richness and abundance of parasites in easily sampled host species may yield an accurate estimate of the species richness and abundance of other hosts in a parasite's life cycle that are difficult to survey directly. Accordingly, we investigated whether prevalence and mean abundance of trematodes could be used to estimate the abundance of one of their host species, diamondback terrapins (Malaclemys terrapin), which are difficult to sample and are designated as near threatened (by the International Union for Conservation of Nature [IUCN Red List]) along some U.S. coasts. As an adult the trematode Pleurogonius malaclemys is specific to terrapins. Its larval stages live first inside mud snails (Ilyanassa obsoleta) and are subsequently shed into the environment where they form external metacercarial cysts on hard surfaces such as snail opercula. The life cycle of P. malaclemys is completed when terrapins ingest these cysts. At 12 sites along the coast of Georgia (U.S.A.), we determined the prevalence of internal P. malaclemys larvae in mud snails (proportion of infected snails in a population) and the prevalence and mean abundance of external trematode cysts. We examined whether these data were correlated with terrapin abundance, which we estimated with mark‐recapture methods. The abundance of external cysts and salinity explained ≥59% of the variability in terrapin abundance. We suggest that dependent linkages between the life stages of multihost parasites make them reliable predictors of host species’ abundance, including hosts with abundances that are challenging to quantify directly.