Invasive exotic plants can persist and successfully spread within ecosystems and negatively affect the recruitment of native species. The exotic invasive Ailanthus altissima and the native Robinia pseudoacacia are frequently found in disturbed sites and exhibit similar growth and reproductive characteristics, yet each has distinct functional roles such as allelopathy and nitrogen fixation, respectively. Spatial point pattern analysis of trees in a silvicultural experiment was used to analyze the potential intraspecific and interspecific interference between these two species by looking at their individual spatial distribution and their spatial association. Analysis of spatial point patterns in the field with Ripley's K indicated that A. altissima and R. pseudoacacia were positively associated with each other along the highly disturbed skid trails in the majority of the field sites. Robinia pseudoacacia was clumped in the majority of the sites, whereas A. altissima was randomly distributed in most sites. Locally, increased disturbances could lead to more opportunities for A. altissima to invade, interact with R. pseudoacacia and other native species and potentially have an effect on the native plant community.

Depressional wetlands are a natural feature of the longleaf pine-wiregrass ecosystem on the southeastern Coastal Plain. Fire is an essential part of the longleaf pine forest with prescribed burns occurring at 1–3 y intervals. In 2000 and 2001 we sampled wetlands whose surrounding uplands had been burned and reference wetlands (i.e., no fire) to determine the short-term changes (<1 mo) in surface water quality. In 2000 pH, alkalinity and dissolved inorganic carbon (DIC) were higher in burned wetlands than reference sites based on ranked ANOVA. In 2001 dissolved organic carbon (DOC) and NH₄-N were higher in burned wetlands than reference ones. Differences between years suggest that field conditions are very important in determining fire's affect on water quality. To clarify our findings we conducted a laboratory experiment where we looked at changes in water quality when exposed to material (wiregrass, dead pine needles and soil) that had undergone simulated fire (muffle furnace at 340 C for 1 h). Results indicated that water exposed to burned soil had elevated pH, alkalinity, DOC, NH₄-N and soluble reactive phosphorus (SRP) compared to unburned soil. Burned wiregrass and pine needles had lower DOC and DIC levels compared to unburned material, but burned wiregrass had higher NH₄-N and SRP concentrations than the unburned treatment. Overall our results suggest that the linkage of fire and water quality of wetlands is through fire's effect on soils rather than vegetation.

We examined the effects of isolation and site size on the abundance, density, emigration and immigration of the butterfly Parnassius smintheus in a series of sub-alpine meadows. Site size was measured either as habitat area or as number of host plants within each meadow. This distinction allowed us to test the hypothesis that population density measured over area (a generalized individuals-area relationship) should tend to decrease with increasing area due to inclusion of more ‘non-habitat’ in larger areas. In general, area measured either as meadow area or host plant abundance explained little deviance in butterfly abundance or movement. Immigration increased with the connectivity (the inverse of isolation) of meadows. We found that individuals-area relationships defined over meadow area showed patterns of decreasing butterfly density with increasing meadow area. This pattern was partially generated by a trend for host plant density to decrease with increasing meadow area. However, this trend was not universal as some small meadows had similar host plant densities to large meadows. Decreasing density with increasing meadow area primarily arose due to decreasing butterfly density with increasing host plant abundance, indicating that multiple mechanisms can produce decreasing population density with increasing area.

The Sydenham River, a tributary to Lake St. Clair in southwestern Ontario, historically supported the richest freshwater mussel community of any river in Canada. Surveys conducted between 1971 and 1991 suggested that the mussel fauna was in decline, with only 13 to 26 of the 33 native species still present. We conducted timed searches (4.5 person-h/site) for mussels at 17 sites in 1997–1998 and additional sampling at several sites in 1998–1999 and found 30 live species, including one new record for the system (Obliquaria reflexa). Four of five species recently designated as endangered in Canada, i.e., Epioblasma triquetra, Villosa fabalis, Simpsonaias ambigua and Epioblasma torulosa rangiana, were found alive in the east branch; the first three species are found nowhere else in Canada. Although the mussel community is in a better state than previously thought, there are signs that conditions are deteriorating. Lampsilis fasciola appears to be extirpated from the system although it is still found in other Ontario rivers. Obovaria subrotunda and L. siliquoidea have significantly declined in the east branch. There is some evidence that L. cardium, Strophitus undulatus and V. iris are also declining in the east branch. Truncilla truncata and Leptodea fragilis may be declining in the north branch. Furthermore, several tolerant species, i.e., Potamilus alatus, Quadrula quadrula, Lasmigona complanata complanata and L. costata are significantly expanding their ranges, especially in the east branch. The latter finding suggests that increases in opportunistic species could provide an earlier warning of environmental degradation than the gradual decline of sensitive species that are often rare to begin with. The primary land use in the Sydenham River basin is agriculture (mainly row crops), and there is an extensive tile drainage system. Increased sedimentation, reduced water clarity and the loss of fish hosts are likely causes of the observed changes in the mussel community. The east branch of the river currently supports 28 species, whereas the smaller north branch sustains only 15 species. These differences were attributed to better water quality, swifter flows and a greater variety of habitat types in the east branch. The mussel fauna of the Sydenham River is nationally and globally important and should be preserved.

Prey populations exposed to different sets of predators often adopt distinct antipredator behaviors. We investigated the refuge use of a freshwater pulmonate snail, Physa integra, in the presence and absence of fish predators. Over 80% of snails in sites with fish used refuge, while only 50% used refuge in sites without fish. Snails in sites with fish were also significantly smaller than snails in sites without fish. In a laboratory experiment, the presence of fish did not alter the habitat use of snails collected from a no-fish site, whereas snails collected from a site with fish used refuge when exposed to predation risk. These results support the hypothesis that P. integra exhibit local behavioral adaptations to their predator regime.

The Topeka shiner (Notropis topeka) is a small native cyprinid species that has declined throughout its range in the Central Great Plains Region of the United States. Declines of the species have been associated with numerous factors including water quality, physical habitat alteration and predation. The N. topeka occurs in the Moniteau Creek Watershed of Cooper and Moniteau Counties of Central Missouri. We studied the Moniteau Creek population of N. topeka over a 1 y period to identify the primary physical, chemical and biological factors associated with population distributions. Fish community composition, water quality data and physical habitat variables were collected at 20 sites distributed across 8 sub-watersheds. Notropis topeka were collected at 8 of the 20 locations; 3 of these sites represent a recent within-watershed range expansion. Notropis topeka were confined to upper reaches of the sub-watersheds in areas typified by relatively high gradient and coarse substrate conditions. Water quality was significantly influenced by both precipitation and locations of sub-watersheds. Although there were isolated sub-watersheds with anthropogenic water quality impacts, we did not detect any relationships between water quality conditions and N. topeka distributions. Collectively, the data indicated that the Moniteau Creek Watershed contains a relatively stable population of N. topeka associated with good water quality and habitat conditions. This study provides baseline data that can be used to identify other watersheds where rehabilitation efforts are most likely to be successful.

Movements and dispersal distances are fundamental aspects of ecology and evolutionary biology. Northern bobwhites (Colinus virginianus) generally are considered the least mobile of all gallinaceous species, but dispersal events of bobwhites (commonly referred to as “shuffling”) are well known. Although dispersal may be a key component in regulating population densities and inbreeding avoidance, few studies have attempted to explain relationships between dispersal, mortality and nest success in northern bobwhites. To examine these relationships, we monitored 957 radio-marked bobwhite from 1991 to 1996. Mean dispersal distance did not differ between sexes (P = 0.699). Mean dispersal distances of adults (2821 m) were shorter than those of juveniles (3411 m; P = 0.042). We found no sex- or age-related differences in survival rates among dispersers and non-dispersers. Despite associated risks with increased movement activity in unfamiliar areas, survival rate was 1.5-times greater for dispersers (Ŝ = 0.72) than non-dispersers (Ŝ = 0.50). Further, we found no relationships between nest success and dispersal distance, suggesting that dispersal distance had little influence on reproductive output of bobwhites. Thus, dispersers may play a key role in bobwhite population dynamics whereby declining populations escape extinction through recruitment from productive populations.

Native tallgrass prairie and wetland habitat in the Prairie Pothole Region of the United States have declined over the past two centuries. Bird communities using these habitats have also experienced widespread declines that are often attributed to severe habitat loss and fragmentation. We estimated the change, or turnover, in bird populations in the Eagle Lake Wetland Complex, Iowa, with ongoing grassland and wetland restoration by linking geographic information system data and bird surveys in different land cover types (hayland, pasture, restored grassland, restored wetland and rowcrop agriculture) during the 1999–2001 breeding seasons. Habitat restoration efforts primarily converted rowcrop agriculture and pastures into grassland and wetland habitat. Based on land conversion, abundances of most species have likely increased in the area, including many species of management concern. Yet a few species, such as killdeer (Charadrius vociferus), have probably decreased in abundance. This estimation approach and these estimates provided a critical first step for evaluating restoration efforts; however, information on demographic parameters, such as nesting success, in restored areas is needed for understanding how restoration ultimately affects bird populations.

Brood cover is a critical component of ruffed grouse habitat during a period when chick mortality may be high. We compared microhabitat characteristics at ruffed grouse (Bonasa umbellus) brood locations with random locations to determine characteristics selected by females with broods in the Appalachian region of Virginia and West Virginia. Females with broods used forested sites with a well-developed overstory canopy (>70%). These sites had a higher abundance of arthropods in the first 3 wk after hatch (P = 0.02), taller ground cover (P < 0.1) and higher percent ground cover (P < 0.1) in the first 6 wk after hatch than random sites. Total woody stem densities were not different (P > 0.1) between brood and random sites as has been found in several studies from more northern sites. Most management prescriptions for ruffed grouse brood habitat are based on increasing hardwood stem densities; our results suggest alternative habitat management techniques that promote ground cover, such as prescribed burning and forest stand thinning, may be more appropriate in the southern Appalachian region.

We investigated how size and spatial arrangement of landscape-level habitat types influenced home range size of ruffed grouse (Bonasa umbellus) in Virginia. Grouse home ranges were overlaid onto a GIS database derived from Landsat TM imagery (30-m pixel scale) and landscape metrics were calculated for 22 habitat types. We used multiple regression to relate home range size to landscape metrics. The amount of core area within the habitat patches in a bird's home range, number of different habitat types, mean shape index of the habitat patches (all positive relations), and amount of high contrast edge (negative relation) predicted home range size (R_adj² = 0.617, P < 0.01). Our results suggested that landscapes containing small (0.5–5 ha), regularly shaped (e.g., square) patches with high interspersion of preferred habitat types and an extensive amount of high contrast edge will decrease ruffed grouse home range size and movement. Such landscapes may contain ruffed grouse habitat requirements within smaller areas, thereby reducing travel costs, decreasing exposure to predators and increasing survival.

Little is known about the natural history of the white-footed vole (Arborimus albipes). We present new information on habitat, diet and range of this mammal as a result of 13 captures in the southern Cascade Range of western Oregon. The study area represents a range extension for the species. White-footed vole encounters were correlated less with distance to water than with basal area and density of alder (Alnus rubra) and percent cover of hazel (Corylus cornuta v. californica). Association with hazel has not been reported previously. Analysis of white-footed vole fecal samples provided the first documentation of mycophagy in this species and of consumption of hazel pollen from unopened catkins. This latter information supports previous speculation that the white-footed vole is semi-arboreal and provides corroborating evidence for the observed correlation with hazel.

Fox squirrel (Sciurus niger) populations are declining in many areas of the eastern United States, and habitat loss may be partly responsible for these declines. We measured habitat variables at fox squirrel refuge sites and random sites and used an information theoretic approach to determine the influence of these variables on probability of a site being used for refuge. There was compelling evidence to support tree and stand level habitat variables as important predictors of refuge sites, but little evidence in support of understory variables. Fox squirrels were more likely to use hardwoods than pines (Pinus spp.) for refuge. Tree size (height and diameter) was positively associated with probability of use as was tree density around the refuge site. Percent debris groundcover, the only understory variable of importance, was positively related to probability of use as a refuge site, but the parameter estimate did not convincingly differ from zero. We conclude that large hardwoods within an open-canopy pine matrix are important as fox squirrel refuge sites.

Franklin's ground squirrel (Spermophilus franklinii) appears to be becoming increasingly uncommon in the eastern portion of its range, but current data on its status in Illinois are lacking. We conducted a mail survey of 166 wildlife professionals from throughout the historical range of the species in Illinois to obtain information pertaining to extant and extirpated populations and local population trends. Locations of potential populations were compared with 106 known historical points of occurrence. Twenty-six sites were chosen for livetrapping surveys to confirm the presence or absence of the species. We considered it likely that Franklin's ground squirrels might persist in these sites due to information provided in the mail survey and/or known historical occupancy. Franklin's ground squirrels inhabited only 3 of the 26 trapping sites; however, we located two other areas of probable occurrence in addition to the locations that we surveyed. While it is clear that Franklin's ground squirrel has declined in Illinois, the magnitude of this decline remains unknown due to the secretive behavior of the species and a lack of knowledge about its ecology. The methods described in this paper are an efficient means of collecting initial information concerning the status of a species that is difficult to observe or about which little is known.

Beavers (Castor canadensis) exhibit wide variations in colony composition and demographics over their broad geographic range, so regional population studies are important for sound management of this species. The objectives of this study were to investigate the: (1) size and sex-age composition of beaver colonies in Illinois, (2) reproductive potential of female beavers in these colonies and (3) efficacy of night-vision surveys versus removal trapping for estimating colony size. We harvested and aged 239 beavers (128 males:111 females) during the 1999–2000 and 2000–2001 trapping seasons. The average colony contained 5.6 beavers. Family groups consisting of a breeding pair and at least 1 offspring composed 86% of these colonies; the other 14% consisted of only a breeding pair. Samples of beavers harvested by commercial trappers were skewed towards yearlings and 2-y olds relative to samples taken from trapped-out colonies. Fetal rates were 3.0, 3.4 and 4.2/female for yearlings, 2-y olds and older adults, respectively. In utero loss was estimated as 13%. Our estimates suggest that over 50% of kits die during the first 6 mo of life. We found no evidence that the presence of older offspring in a colony allowed parents to raise more kits. Night-vision surveys conducted 10 m downwind from the den for 2.5 h after sunset underestimated the size of colonies, accounting for only 55% of the beavers present.

We investigated relationships between canopy closure, shrub cover and the use of coarse woody debris as a travel path by eastern chipmunks (Tamias striatus) in the north central United States. Fine scale movements of chipmunks were followed with tracking spools and the percentage of each movement path directly along coarse woody debris was recorded. Availability of coarse woody debris was estimated using line intercepts. We predicted that, if chipmunks used coarse woody debris to reduce their risk of predation, movement along coarse woody debris would be greater for animals tracked at sites with open canopies and thick shrub cover. Travel along coarse woody debris was negatively associated with canopy closure and positively associated with the percent of coarse woody debris available at a site and the percentage of shrub cover at a site. Sex and age of eastern chipmunks did not appear to influence the amount of use of coarse woody debris. Our results suggest that coarse woody debris is more important to chipmunks in areas with open canopies and thick shrubs and are consistent with the hypothesis that coarse woody debris provides chipmunks with some protection from predators.

Historically, bison were of great importance to the grassland ecosystem, affecting plants and other organisms directly through grazing and indirectly by creating soil disturbances, such as wallows. When bison were reintroduced to the Konza Prairie Biological Station, Kansas, they reactivated relic wallows as well as created new ones. Wallows, like other ephemeral pools, may be used by organisms as aquatic habitat and as breeding sites. The objective of our study was to systematically monitor bison wallows after they filled and to ascertain their use by amphibians. We also examined long-term climatic records from the Konza Prairie area to assess the past viability of bison wallows as breeding habitats for anurans, which must complete metamorphosis before wallows dry. The amount of precipitation and cool temperatures required to prolong the hydroperiod necessary for completion of metamorphosis occurred in only about 20% of the years examined. Bison may have been important in the life histories of prairie anurans by creating “pools” in the form of wallows that could be used as breeding sites. However, more information about the life history of individual species of anurans is needed before viability of bison wallows as a breeding habitat can be determined.

We documented mean and maximum body mass, mass accretion patterns and antler development patterns of Rocky Mountain elk in Michigan. Mean body mass of bulls averaged 9–11% heavier, and maximum body mass 23–27% heavier, in Michigan than in other Rocky Mountain elk populations. Mean live body mass of cows averaged 11% heavier in Michigan, but mean eviscerated body mass did not differ. Maximum body mass of cows was 10–24% heavier in Michigan. Body mass peaked at age 7.5 for bulls and 8.5 for cows, similar to other Rocky Mountain elk populations despite the greater body mass achieved in Michigan. Sexual dimorphism in bull and cow body mass increased until peak body mass was attained, whereupon bulls were ∼38% heavier than cows. Antler development of bull elk peaked at age 10.5, comparable to other Rocky Mountain elk populations. Relations between antler development and body mass within age classes were highly variable, but generally weak. Greater body mass seen in Michigan, and the peaking of antler development well after body mass in bulls, suggested a phenotypic response to nutritional conditions that allow Rocky Mountain elk in Michigan to maximize the species growth potential.

In tree holes, leaf scraping scirtid beetles increase the rate at which leaf litter is converted to fine particles, which may benefit fine particle feeding mosquitoes if these fine particles are valuable to mosquitoes. We tested whether the products of scirtid feeding are a valuable food resource for mosquito larvae [Ochlerotatus triseriatus (Say)] by introducing different amounts of scirtid feces to mosquito larvae and measuring mosquito performance. Mosquito larvae survived longer and developed to later instars in treatments with many scirtids (and, therefore, a lot of feces) compared to treatments with few or no scirtids. This result suggests that scirtid feces (and attached microorganisms) constitute a valuable food resource for O. triseriatus. Thus, other members of tree hole communities may have complex effects on the population growth of O. triseriatus.

Declines in amphibian species have become a worldwide concern. This concern is heightened by predicted global climatic changes that may result in shifts in current patterns of local precipitation. Because of the potential dependence of successful breeding by amphibians on rainfall patterns, we tested the relationship between breeding by the rare gopher frog (Rana capito) and rainfall. We used data collected from long-term (1988–2000) monitoring of breeding activity at two ponds (one ephemeral, one semi-permanent) located in the Lower Coastal Plain of Alabama. Egg-mass counts at both ponds showed a significant positive relationship between reproductive effort and rainfall during the breeding season. Individuals of R. capito disperse for considerable distances across a xeric landscape and wet conditions allow greater access to breeding sites for more distantly dispersed frogs. We did not find a significant trend in the number of egg masses laid over time at the ephemeral pond; however, there was a significant increase in egg masses deposited at the semi-permanent pond during the course of this study. Understanding the importance of environmental variables such as rainfall will hopefully lead to the successful conservation of this and other species of amphibians with similar environmental requirements.

The common nighthawk (Chordeiles minor) is a crepuscular species known to use visual signals for agonistic and sexual communication. To test the hypothesis that white plumage patches function in visual communication of reproductive quality, we measured the size of white patches present on the wing, tail and throat of the otherwise cryptic plumage of males of this species belonging to three age classes. There was a significant increase in wing-band and tail-band size with age, but no significant increase in throat-patch size. We argue that these white patches, combined with behavioral displays, likely function as visual signals of male quality.

We live-trapped small mammals at 12 sites and compiled data from 3 previous live-trapping studies to document the distribution of the eastern chipmunk (Tamias striatus) in the Shawnee National Forest (SNF) in southern Illinois. Chipmunks were not captured at sites in large areas of the eastern SNF. We collected data on canopy composition and coarse woody debris (CWD) at 8 sites where chipmunks were absent and 5 sites where they were present. Canopy composition and CWD did not differ significantly between sites with and without chipmunks. We could not recognize any geographic barriers that would prevent dispersal into the eastern SNF by chipmunks. Thus, the absence of chipmunks in the eastern SNF seems inexplicable at this time.