Patterns Of Site Use Research Articles

Assessing the Movements, Habitat Use, and Site Fidelity of the Giant Freshwater Whipray (Urogymnus polylepis) with Acoustic Telemetry in the Maeklong River, Thailand

We used acoustic telemetry to assess site fidelity, movement patterns, and habitat use within the lower Maeklong River, Thailand, by 22 giant freshwater whipray Urogymnus polylepis. This study is the first of its kind for this rare, endangered species, and it begins to fill critical information gaps about its ecology and life history. Study animals were tagged subcutaneously in the dorsal area with acoustic transmitters and tracked for 12 months using a fixed array of eight receivers. Receivers were positioned within an 18 rkm section of the Maeklong, starting approximately 4 rkm upstream from the mouth. We calculated individual residency indices, tracked longitudinal movements, and assessed annual and seasonal patterns of site use. We also investigated spatial use patterns, diel activity patterns, and relationships of temperature and site fidelity. We detected 86% of our tagged whiprays, 53% of which were detected for the majority of the study period. Whiprays exhibited high site fidelity across seasons. Individuals made long longitudinal movements within the site for much of the study period but seemed to remain closer to the estuary during the second half of the rainy season and early winter. All receivers had large numbers of detections, but upstream receivers were visited for longer time durations than downstream receivers. A receiver in the middle of the study area had the highest detection rate, but low detection durations, suggesting that this receiver is in a migration corridor. A mix of immature and mature males and females was present in the site throughout the study period, suggesting that this area is not exclusively a breeding or nursery site. However, the high site fidelity suggests that this is an important aggregation site for the species. Effective conservation measures may include conservation zones and a shrimp reintroduction program upstream, ensuring fish passage through the middle of the site, and regulating traffic and pollution downstream. We found acoustic telemetry to be an effective study method and encourage its use to improve understanding of the giant freshwater whipray.

Effects of human-induced habitat changes on site-use patterns in large Amazonian Forest mammals

The Amazon is one of the most diverse biomes around the globe, currently threatened by economic and industrial development and climate change. Large mammals are keystone species, playing an important role in ecosystem structure and function as ecological engineers, while being highly susceptible to deforestation, habitat degradation, and human exploitation. Using a unifying hierarchical Bayesian spatial approach, we examine the site-use patterns of four large Amazonian Forest mammals and their relationships to anthropogenic factors at a biome-wide scale. Our results showed that species’ patterns of site use are correlated with human induced habitat changes, and that this correlation is species-specific. The white-lipped peccary shows highest site-use estimates within strict protected areas, affected by proximity to urban areas and benefiting from indigenous territories, the tapir responding slightly to proximity to burned forested areas, while the giant armadillo and the jaguar were primarily affected by vegetation cover loss; disturbances related to the colonization of the Amazon. Our findings contribute to the understanding of how human-induced environmental changes influence the site-use patterns of these four large mammals, and inform future conservation and land use planning. Transboundary conservation efforts, empowering and integrating native (indigenous and non-indigenous) communities in land governance schemes, involving the private sector and securing the commitment of developed countries are important paths for the protection and sustainability of the globally-crucial Amazon rainforest.

A micro-geoarchaeological view on stratigraphy and site formation processes in the Middle, Upper and Epi-Paleolithic layers of Sefunim Cave, Mt. Carmel, Israel

This paper presents a micro-geoarchaeological study carried out on the sedimentary sequence exposed at the entrance of Sefunim Cave, Israel, a sequence that spans from the Middle Paleolithic to the early Epipaleolithic periods. Using FTIR and micromorphological techniques, we investigated the stratigraphic sequence to reconstruct patterns of site use and archaeological formation processes. We identified formation processes that are common among Paleolithic caves sites in the Southern Levant, mainly the deposition of local terra rossa through colluvial sedimentation. Taphonomic disturbances of the deposits range from minimal to moderate, exhibited mainly by root and burrowing activity, but with no evidence for significant transport of archaeological materials. While the upper layers (II–III) are decalcified, the precipitation of secondary calcite results in increasing cementation of the sediments with depth in the lower layers (V–VII). We observed variation at the microscopic scale and identified an inverse correlation between human and carnivore activity throughout the layers. We observed human activity by the presence of micro-archaeological materials such as chert, bone, charcoal, rubified clay, burnt bone and shell, and wood ash. We observed carnivore activity by the presence of phosphatic grains and coprolite fragments as well as chewed and digested bones. We conclude that human activity at the site was characterized by episodes of varying intensity, based on the frequency of archaeological finds within the different layers. The alternating episodes of human and carnivore activity at Sefunim Cave may demonstrate the close-knit interactions and reciprocal relations that humans and carnivore shared at Paleolithic caves.

Coherent changes in wood charcoals, site occupation and lithic technology across the MIS 4/3 transition at Klein Kliphuis rock shelter, South Africa

AbstractWe explore the correspondence between changing palaeoenvironments, patterns of site use, and lithic technology at the rock shelter site Klein Kliphuis (South Africa) across the interval 65–55 000 years before present. This period coincides with the termination of Marine Isotope Stage (MIS) 4, and the disappearance of an iconic late Pleistocene archaeological unit known as the Howiesons Poort. Wood charcoals indicate sufficient soil moisture around Klein Kliphuis throughout the Howiesons Poort to support diverse tree species at a time when site occupation was relatively intense. At least some fuelwood‐gathering in this period may have been undertaken to support heat treatment of silcrete, which was the dominant lithology in tool production. A coherent set of changes occurs across the MIS 4/3 transition: occupational intensity declines, tracked by declining diversity of fuelwood species, an increase in the proportion of charcoals from shrubs and small flowering plants, lower prevalence of silcrete, and less heat treatment. While declining soil moisture is implied, there appears to be a significant change in behaviour relating to site usage, whereby foraging for dense fuelwoods was replaced by the construction of ‘fast fires’ that may reflect briefer visits and increased forager mobility in early MIS 3.

Fit for purpose: investigating adaptations in late Pleistocene lithic technology to an island environment at Buang Merabak, New Ireland, Papua New Guinea

ABSTRACTThe occupation of Buang Merabak, a cave located on the island of New Ireland, by 42,000 years ago demonstrates that the colonisation of the Bismarck Archipelago occurred soon after that of Sahul. This provides the opportunity to consider the adaptation of small groups of people to a depauperate island environment. An analysis of a lithic assemblage from Buang Merabak was used to consider how technological organisation reflects changing patterns of site use and subsistence strategies from the late Pleistocene through to the early Holocene. A strategy of small simple flake technology was identified, which would have allowed site occupants flexibility in the face of fluctuating patterns of faunal resource use. During the late Pleistocene, a broad range of local lithic materials were used expediently. Gradual change occurred in the early Holocene to a smaller variety of materials with dominant use of local chert flakes and conservation of specific volcanic materials.

Reindeer Demographics at Iarte VI, Iamal Peninsula, Arctic Siberia

ABSTRACT This study focuses on constructing a demographic profile for a large set of reindeer (Rangifer tarandus) remains from the Iron Age Iarte VI site on the Iamal Peninsula in Siberia. Iarte VI produced one of the largest reindeer assemblages in the entire Arctic, totalling ∼22,000 specimens. Age assessment is conducted by examining teeth eruption sequences in 686 mandibular fragments. Sex identification is based on analysis of 595 os coxae through visual observation of the acetabulum ventro-medial rim or border. Our assessments demonstrate that inhabitants at Iarte VI accessed various reindeer age categories, with adults being the most often utilised group of animals. Adults were found in all excavated sections and cultural strata at the site and consisted of both males and females. Other age groups such as newborns, yearlings, and juveniles were also present but in smaller quantities. The majority of the sub-adult individuals were under six months of age, indicating the use of this location during the warmer seasons, most often in fall. This seasonal pattern of site use is similar to historic seasonal migrations by many Indigenous reindeer herding families, who move north to utilise the tundra of Iamal Peninsula during the spring, summer, and early fall.

Coastal subsistence and settlement at the Hane dune site, Ua Huka (Marquesas Islands): New insights from Pacific rat (Rattus exulans) stable isotope analysis

The Pacific rat (Rattus exulans) is a small commensal omnivore; its close association with humans throughout Polynesian prehistory suggests that dietary change in this species can provide insight into localized trends in site ecology and activity. Carbon and nitrogen stable isotope analysis was applied to archaeologically recovered Pacific rat remains from recent re-excavations of the Hane dune site, Ua Huka Island (Marquesas Islands) to investigate prehistoric patterns of human subsistence and site use. Our results indicate that early subsistence at Hane was marine-oriented and focused on exploitation of high trophic level marine carnivores including offshore fish and seabirds. A rat dietary shift in later prehistory (Phase III) points to greater investment by Marquesan people towards terrestrial arboriculture and animal husbandry, as well as to restriction of fishing practices to largely inshore exploitation. These results provide a new line of evidence towards interpreting the archaeofaunal record at Hane. Stable isotope analysis of small commensal species complements archaeofaunal and ethnographic data to provide further resolution to localized patterns of site use and subsistence practices. This analysis advances a low-impact method for investigating past environments and human activity.

Neandertal mobility and large-game hunting: The exploitation of reindeer during the Quina Mousterian at Chez-Pinaud Jonzac (Charente-Maritime, France)

Neandertals were effective hunters of large ungulates throughout their geographic and temporal ranges. Equipped with this knowledge, researchers in paleoanthropology continue to seek insight on the relationships between hunting and subsistence strategies with other components of the Neandertals’ niche, such as mobility, site use, and lithic technology. The Quina Mousterian deposits from the rockshelter site of Chez Pinaud Jonzac (Charente-Maritime, France; hereafter Jonzac) offer an excellent opportunity to pursue these issues. This paper focuses on the extensive and well-preserved skeletal remains of reindeer (Rangifer tarandus) recovered from recent excavations of the site, representing at least 18 individuals that were hunted by Neandertals during the fall through winter. Our zooarchaeological results indicate that all ages of reindeer were hunted but adult individuals predominate. No bias is evident in the comparable frequencies of males and females. These prey were butchered on-site, with abundant evidence of meat filleting and marrow exploitation. In the excavated sample, the absence of hearths and the almost complete lack of burned bones or stones suggest that Neandertals were not using fire to assist with processing the reindeer carcasses. The zooarchaeological results presented here indicate that reindeer were hunted during a restricted window of time when they were seasonally abundant in the local area near Jonzac. Taken together with the lithic industry based on bifacial elements, the evidence is consistent with a pattern of site use by highly mobile hunter-gatherers making frequent, short-term visits. Ongoing research at Jonzac and other Quina Mousterian localities will contribute to a better understanding of Neandertal behavior during cold climate phases.

Habitat selection and waterbody-complex use by wintering Gadwall and Shoveler in South West London: Implications for the designation and management of multi-site protected areas

The degree to which Special Protection Area (SPA) designation reflects ecological reality is of critical importance to wildlife conservation. We examined whether the designation of a large SPA designated to conserve wintering waterfowl (chiefly Gadwall Anas strepera and Northern Shoveler Anas clypeata), reflected the birds’ habitat preferences and their use of the SPA in the context of the broader geographic area. To do this, 67 discrete waterbodies in and around the South-West London Waterbodies Special Protection Area (SWL SPA) were surveyed regularly each winter from 2004/5 to 2006/7, and new analytical methods developed, to investigate habitat selection and multiple-site use by the birds. Significant pressure on these waterbodies for mineral extraction, development and recreation, together with a long history of human usage has resulted in a wide range of habitats and conditions for these wildfowl.We found that Gadwall and Shoveler were able to adjust their site preferences and patterns of site use in response to changes in food resources and other ecological variables both within and between winters. Akaike's Information Criterion (AIC) was used to model the distribution of wildfowl between sites using a large number of physical and ecological predictor variables. This showed that Gadwall and Shoveler differ in many of their habitat preferences, to the extent that managing a site for one will not necessarily directly benefit the other.At the time of this study the habitat preferences of Gadwall and Shoveler do not closely match the ecological condition of the SWL SPA waterbodies. Furthermore, an investigation into the use of multiple sites by Gadwall and Shoveler indicated that although there is evidence for populations of wintering birds using groups of waterbodies in the SW London area, their patterns of site use do not closely match the distribution of the seven separate SPA component waterbodies.We provide guidelines for managing habitats for Gadwall and Shoveler, and suggest that in addition to bird counts the SPA designation process for multi-site protected areas should consider the behaviour, habitat requirements and the influence of human disturbance on the species concerned. In this instance, the patterns of wildfowl site use present a reasoned argument for the inclusion of additional sites in the SW London Waterbodies SPA, or for dealing with the SPA in a different manner to a site with a more contiguous boundary.

Scale and pattern of broadnose sevengill shark Notorynchus cepedianus movement in estuarine embayments

The detailed movements of 32 acoustically tagged broadnose sevengill shark Notorynchus cepedianus were documented in and around north-east Pacific Ocean estuarine embayments from 2005 to 2007. Arrangements of passive acoustic receivers allowed analysis of movement at several spatial scales, with sex and size examined as possible factors influencing the pattern and timing of these movements. Notorynchus cepedianus exhibited a distinctly seasonal pattern of estuary use over three consecutive years, entering Willapa Bay in the spring, residing therein for extended periods of time during the summer and dispersing into nearshore coastal habitats and over the continental shelf during the autumn. Notorynchus cepedianus within Willapa Bay showed spatio-temporal patterns of segregation by size and sex, with males and small females using peripheral southern estuary channels early in the season before joining large females, who remained concentrated in central estuary channels for the entire season. Individuals displayed a high degree of fidelity not only to Willapa Bay (63% were documented returning over three consecutive seasons), but also to specific areas within the estuary, showing consistent patterns of site use from year to year. Cross-estuary movement was common during the summer, with most fish also moving into an adjacent estuarine embayment for some extent of time. Most winter and autumn coastal detections of N. cepedianus were made over the continental shelf near Oregon and Washington, U.S.A., but there were also examples of individuals moving into nearshore coastal habitats further south into California, suggesting the feasibility of broad-scale coastal movements to known birthing and nursery grounds for the species. These findings contribute to a better understanding of N. cepedianus movement ecology, which can be used to improve the holistic management of this highly mobile apex predator in regional ecosystems.

Moments in Time: Differential Site Use Patterns at Meadowcroft Rockshelter (36WH297)

Meadowcroft Rockshelter (36WH297) currently manifests the longest, if explicitly episodic, occupational sequence in the Americas. Interestingly, despite the long persistence of an essentially stable seasonal visitation pattern which is centered upon latest summer through mid- to late-fall site use, the intensity of rockshelter utilization (measured in length of visitation interval and/or persons per visit) is highly variable. Prior to and after Late Archaic/Transitional and Early Woodland times (ca. 4000–100 B.C. uncalibrated), the pattern of site visitation by any index is rather light. During the Late Archaic/Transitional and Early Woodland intervals, site utilization is much heavier based on all available lines of evidence. The spatial and temporal patterns of site use at Meadowcroft during the Holocene are detailed and related to broader patterns of Cross Creek Drainage-wide prehistoric visitation. Several potential explanations are offered for the heavier pattern of site use documented for the Late Archaic/Transitional and Early Woodland periods.

Haulout site selection by southern elephant seals at Marion Island

Using data from an ongoing mark–resight programme at Marion Island, we tested empirically whether southern elephant seals prefer certain terrestrial sites to others during the breeding, moulting and winter haulouts, and whether the pattern of site use is the same for different age and sex groups. Southern elephant seals preferred some sites, while discriminating against other sites, with different age and sex classes using different sites for certain haulout events. Wintering young animals did not show strong site selection. Some popular sites were used for all haulouts by all age and sex groups, and apparently have all the requirements of a good site for terrestrial haulout by southern elephant seals. Site selection becomes more apparent with age, suggesting the role of haulout experience in site selection.

Haulout site selection by southern elephant seals at Marion Island

Using data from an ongoing mark–resight programme at Marion Island, we tested empirically whether southern elephant seals prefer certain terrestrial sites to others during the breeding, moulting and winter haulouts, and whether the pattern of site use is the same for different age and sex groups. Southern elephant seals preferred some sites, while discriminating against other sites, with different age and sex classes using different sites for certain haulout events. Wintering young animals did not show strong site selection. Some popular sites were used for all haulouts by all age and sex groups, and apparently have all the requirements of a good site for terrestrial haulout by southern elephant seals. Site selection becomes more apparent with age, suggesting the role of haulout experience in site selection.

Internet-Based Interactive Health Intervention for the Promotion of Sensible Drinking: Patterns of Use and Potential Impact on Members of the General Public

Background Heavy drinking is responsible for major health and social problems. Brief interventions have been shown to be effective, but there have been difficulties in reaching those who might benefit from them. Pilot studies have indicated that a Web-based intervention is likely to be acceptable to heavy drinkers and may produce some health benefits. However, there are few data on how many people might use such a program, the patterns of use, and potential benefits.Objectives The aim was to examine the demographic characteristics of users of a free, Web-based, 6-week intervention for heavy drinkers and to describe the methods by which users identified the site, the pattern of site use and attrition, the characteristics associated with completing the program, and the self-reported impact on alcohol-related outcomes.Methods Cohort study. Visitors to the Web site were offered screening with the Fast Alcohol Screening Test, and those scoring above the cutoff for risky drinking were invited to register with the program. Demographic information was collected routinely at registration, and questionnaires were completed at the end of weeks 1 and 6. The outcome measures assessed dependency (Short Alcohol Dependency Data Questionnaire), harms (modified Alcohol Problems Questionnaire), and mental health (Clinical Outcomes in Routine Evaluation–Outcome Measure).Results The records of 10000 users were analyzed. The mean age was 37.4 years, 51.1% were female, 37.5% were single, and 42.4% lived with children. The majority were White British, lived in the United Kingdom, and reported occupations from the higher socioeconomic strata. Over 70% connected to the Down Your Drink (Down Your Drink) site from another Internet-based resource, whereas only 5.8% heard about the site from a health or other professional. Much of the Web site use (40%) was outside normal working hours. Attrition from the program was high, with only 16.5% of registrants completing the whole 6 weeks. For those who completed the program, and the final outcome measures, measures of dependency, alcohol-related problems, and mental health symptoms were all reduced at week 6.Conclusions The Web-based intervention was highly used, and those who stayed with the program showed significant reductions in self-reported indicators of dependency, alcohol-related problems, and mental health symptoms; however, this association cannot be assumed to be causal. Programs of this type may have the potential to reach large numbers of heavy drinkers who might not otherwise seek help. There are significant methodological challenges and further research is needed to fully evaluate such interventions.

QUANTIFYING SPATIAL PATTERN WITH EVENNESS INDICES

Quantifying the spatial distributions of organisms in simple and meaningful ways is important for understanding the ecology and habitat needs of species subject to anthropogenic disturbances. Most multi‐species conservation and management programs do not yet account for the variation of space‐use patterns exhibited by species preferring the same habitat type. To measure species' space‐use patterns as a step toward determining habitat needs, we suggest using evenness indices. Although commonly used in characterizing communities (i.e., as a measure of species diversity), these indices are suitable for characterizing many other ecological patterns, including patterns of site use by individuals.We investigate the statistical properties of five indices (Camargo's index of evenness, E′; Simpson's index of evenness, E1/D^; Lloyd's index of mean crowding, J; Smith‐Wilson index Evar; and Dispersion index, DL, a variant of the Shannon diversity index) to evaluate their utility for quantifying broad‐scale spatial patterns of migratory shorebirds. We use a Monte Carlo simulation approach to compare these indices for their (1) ability to characterize a wide range of spatial patterns (from even to patchy); (2) ability to discriminate among distributions; and (3) robustness to incomplete sampling. In addition, we compare the ability of these indices to characterize spatial dispersion for four species of shorebirds migrating through the United States: Killdeer (Charadrius vociferus), Semipalmated Plover (C. semipalmatus), Sanderling (Calidris alba), and Red Knot (C. canutus).Overall, we recommend Camargo, Simpson, and Lloyd indices for quantifying spatial dispersion. All three indices gave precise and unbiased estimates once 35 or more sites (3.5% of 1000 simulated sites) were sampled randomly, regardless of the degree of patchiness. Nonrandom sampling resulted in biased estimates until a much greater proportion of sites (at least 30–50%) were sampled, highlighting the importance of site selection in sampling programs. Our analysis of shorebird spatial patterns revealed that evenness indices discriminate well among the species we considered, ranking Killdeer as most dispersed and Red Knot as most aggregated. Our results agree with earlier (independent) assessments of these species' migration strategies and illustrate how simple univariate metrics may be useful tools for characterizing complex spatial patterns.

PHABSIM modelling of Atlantic salmon spawning habitat in an upland stream: testing the influence of habitat suitability indices on model output

This paper reports the findings of research designed to assess the ability of PHABSIM to predict Atlantic salmon Salmo salar spawning habitat in the Girnock Burn, a tributary of the River Dee in northeast Scotland. It used an 18-year spawning data record to assess: (a) the ability of PHABSIM to predict between-year differences in the availability of habitat at the study site; (b) the ability of PHABSIM to predict patterns of relative suitability across the site; and (c) the influence of different Habitat Suitability Indices (HSIs) on the model's predictions with respect to (a) and (b). Predictions of between-year and within-site habitat availability based on ‘utilization’ and ‘preference’ HSIs developed in the Dee catchment corresponded significantly (chi-squared and regression tests, P < 0.05) with the use of the site by spawning fish. However, predictions based on utilization HSIs developed in streams in southern England did not correspond significantly with patterns of site use. Results of the study indicate that PHABSIM is capable of predicting Atlantic salmon spawning habitat in upland streams such as the Girnock, but that the use of appropriate HSIs is critical. Copyright © 2005 John Wiley & Sons, Ltd.

Competition, predation, and the distributions of four desert anurans.

Several studies have shown that larval competition and susceptibility to predation affect distributions of amphibian assemblages across ephemeral and perennial habitats. However, few studies have examined mechanisms affecting distribution patterns and site use of anurans adapted to highly ephemeral habitats. This study examines hypotheses about competition and predation as mechanisms creating non-overlapping patterns of site use in four anurans that breed in highly ephemeral habitats: Scaphiopus couchii (Couch's spade-foot toad), Gastrophryne olivacea (narrow-mouthed toad), Bufo speciosus (Texas toad), and Bufo punctatus (red-spotted toad). These four anurans showed a significantly nonrandom pattern of co-occurrence. Only 12% of 95 ephemeral breeding sites surveyed were occupied by more than one species. We tested the hypotheses that non-overlapping use of breeding sites was due to activity rates of their tadpoles that in turn reflect their competitive ability and susceptibility to predation. Tadpoles of S. couchii were significantly more active and more susceptible to predation than were tadpoles of G. olivacea, B. speciosus, and B. punctatus. The masses of G. olivacea, B. speciosus, and B. punctatus were less when they were reared with S. couchii, demonstrating the possible competitive dominance of S. couchii. These results suggest that the competitive ability of S. couchii may play a role in excluding G. olivacea, B. speciosus, and B. punctatus from very ephemeral breeding sites, and that susceptibility to predation could play a role in excluding S. couchii from breeding sites of longer duration that are more likely to be colonized by aquatic predators.

CHARACTERISTICS AND POSSIBLE FUNCTIONS OF TRADITIONAL NIGHT ROOSTING AGGREGATIONS IN RUBYSPOT DAMSELFLIES

Summary Many species of animals congregate into groups when roosting. While studies exploring roosting behavior are common, relatively few detailed, quantitative studies have been done on the roosting behavior of insects, and the adaptive value of roosting aggregations are still unclear for most edible (non-distasteful) species of any taxon. We investigated night roosting aggregations of the rubyspot damsele y, Hetaerina americana, along a creek in the Coastal Range Mountains of California. Both male and female rubyspots were found in roosting aggregations, although the aggregations tended to be male-biased relative to the population sex ratio. Rubyspots roosted on the west side of slow moving sections of the creek; within this habitat they were highly aggregated but were not associated with any particular habitat features. The spatial pattern of site use tended to change gradually over time and sites with a relatively large number of individuals were more likely to be used on subsequent nights. These results suggest that within suitable habitat, the specie c locations of roosting aggregations were traditional (socially learned). Rubyspot roosting patterns, when taken in combination with other aspects of this species’ biology, do not support habitat limitation, thermal or desiccation benee t, foraging, and aposematic hypotheses for the function of rubyspot roosting aggregations. Rather, the roosting aggregations most likely serve an antipredator function or are the result of using conspecie cs to choose safe sites.

Users and navigation patterns of a science World Wide Web site for the public

We report here initial findings of a multi-year study of public use of a World Wide Web site for science information. “The Why Files” strives to provide “the science behind the news” in story narratives that contain opportunities for both linear and non-linear navigation. We report results of two studies, one using survey data and another using computer-collected audit trails. The survey revealed that the typical user was male and well-educated, a pattern that reflects both Web users generally and the science-attentive segment of the public particularly. Audit trail data indicated that the site reached as many as 25,000 different individuals during a two-week measurement cycle. The typical pattern of site use was linear, with individuals making heavier use of in-text navigation features than of graphic ones such as page-turning buttons and page numbers. Additional information in glossaries, bibliographies, or via links to other Web sites went largely unused.

Flight Costs, Flight Range and the Stopover Ecology of Migrating Birds

1. Flight range equations are a central component in the analysis of avian migration strategies. These equations relate the distance that can be covered to the fuel load that the birds carry. Models of stopover decisions deal with the question of how birds should react to variations in fuel deposition rates. Time-minimization models generally predict an increasing relationship between departure fuel load and fuel deposition rate. 2. We show that quantitative details of predictions derived from optimality models depend critically on the flight range equation that is used. We use two classes of flight range equations: one class is based on theoretical assumptions of aerodynamics; the other is based on empirical measurements of metabolism during flight. 3. Most empirically derived equations can be written as Y(x) = c[1-(1 + x) -ζ ], where 0 < ζ < 1, and c is a constant that includes morphological traits and lean body mass. 4. Patterns of site use and departure loads in environments with discrete stopover sites depend in significant ways on flight costs. 5. Flight range estimates that are based on empirically derived, multivariate equations are sensitive to errors in the estimates of exponents of the equations. Varying some exponents within their confidence limits can alter flight ranges by an order of magnitude.