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The northern pitcher plant (Sarracenia purpurea) receives some of its nutrients from the decomposition of prey that fall into its pitcher-shaped leaves. The majority of prey consists of ants, beetles, spiders, and slugs, and in rare cases, frogs and lizards. Here we report on the unusual occurrence of 22 Red-spotted Newt larvae (Notophthalmus viridescens viridescens) trapped within northern pitcher plants during a nutrient manipulation experiment in a Massachusetts bog in the summer of 2003. Newts were found among the larger of our experimental plants, but were not associated with any particular nutrient-addition treatment. High nitrogen levels in newts could contribute significantly to the nutrient budget of northern pitcher plants. Furthermore, this observation suggests that the trapping of amphibian prey by northern pitcher plants might not be as rare an event as previously believed.
We evaluated three possible functions of clonal growth related to genet persistence in the root-suckering understory tree pawpaw, Asimina triloba (L.) Dunal: (1) risk spreading through multiplication of stems, (2) enhanced establishment and survival of new stems, and (3) horizontal expansion growth of patches. The number, diameter growth, and spatial distribution of annual stem recruits were examined over three years in a natural population of pawpaw. The rate of stem recruitment was consistently higher than stem mortality. We found no difference in stem turnover rate for patches of different size, indicating that stem production is more than high enough to avoid patch extinction. Although newly formed stems were considerably smaller than previously established stems, they grew and survived as well as established stems. We found no evidence for clonal growth contributing to extensive horizontal expansion of patches. Our results suggest that ensuring survivorship of new stems is the main ecological role of clonal growth in pawpaw.
The exotic tree, Acer platanoides, is increasing in forests of northeastern North America, largely within the range of its native congener, Acer saccharum. A combination of field and controlled experiments was used on seeds and seedlings of these congeners to determine species characteristics that may be contributing to these floristic changes. Acer platanoides experienced lower rates of seed predation than A. saccharum in field experiments. Differences in the dispersal and allocation characteristics of the two species were small and not likely to explain the relative success of A. platanoides. Greenhouse-grown seedlings of A. platanoides were much larger than those of A. saccharum because of differences in seed size, not differences in growth rate. These data suggest that preferential seed predation and initial seed size differences may explain greater relative success in Acer platanoides seedlings.
Frugivores and fruit-producing plants often have a mutualistic relationship in which plants provide animals with nutritious fleshy pulp in return for the dispersal of seeds within the fruit. Although the selection and dispersal of invasive plant species by birds has major implications for native animals, plants, and communities, few studies have focused on whether birds select invasive versus native fruits. I compared fruit removal and fruit choice by birds, and fruit energy content of two invasive plant species, Lonicera tatarica and Rosa multiflora, and two native plant species, Cornus amomum and Viburnum opulus, in central Maine. Frugivores preferentially consumed fruit from L. tatarica and C. amomum, and they did not discriminate between R. multiflora and V. opulus during choice trials. Although the two native plant species had significantly higher caloric content than the two invasive species, higher energy density of native plants was not directly correlated with more rapid fruit removal or fruit preference.
Understanding space-use patterns of highly mobile animals, such as woodland caribou (Rangifer tarandus caribou Gmelin), is required for ecosystem conservation. We consider the use of lakes in winter as important habitat for woodland caribou both to reduce predation risk and acquire food. To test scale differences relative to caribou use of ice-covered lakes in winter, we compare the use of ice-covered lakes within a regional study area and within sub-regional landscapes at two spatial levels: (1) seasonal selection of winter ranges and (2) daily locations. We used 100% minimum convex polygons with a 500-m buffer for winter ranges, and 500-m radius buffer around individual radio telemetry locations of 27 caribou from 1995 to 2000 as spatial measures of use of lakes of various dimensions by caribou. In the winter-range analysis, caribou used areas with more lakes in the 5–100-ha size class, including lakes with more perimeter, larger area, and higher fractal dimensions as compared with the relative distribution of available lakes. These patterns were confirmed at the regional level (Manitoba border in the west to the Hudson Bay lowlands to the east) and at the sub-regional level. At the finest level of resolution of daily locations, caribou selected lakes with greater area and perimeter in the west but not in the east. Our findings should be considered when developing local plans for forest management and designing landscapes where the conservation of woodland caribou is a goal.
A cytological and morphological survey of the black flies of Prince Edward Island revealed 20 species of which 13 represent new provincial records. An additional three species have been recorded in the literature but were not found in this study. All 20 species are widely distributed on the North American mainland. Three species are significant pests of humans, six feed on birds, two species do not take blood, and the remaining species feed on non-human mammals.
Phoxichilidium tubulariae exhibits an encysted protonymphon development. Its fast developmental mode reduced the typical number of pycnogonid molts and developmental time from months as described for other pycnogonid species to fewer than 21 days. This developmental strategy exploited the seasonal abundance of Tubularia larynx. The larvae hatched, infested the hydroid, and developed inside the gastrovascular cavity. The larvae developed for several molts and then emerged, destroying the hydranth. Annual population dynamics of P. tubulariae were seasonal; density of adult animals was highest in mid-to-late summer with reproduction being greatest in July and August. The abundance of pycnogonids peaked as the hydroid population declined.
The flight activity of the apple leaf midge, Dasineura mali (Kieffer), was determined in the field and laboratory. Males and females began emerging at the onset of the photophase. In the field, delta-shaped traps baited with 6 virgin females caught males exclusively, with the most abundant catches on the ground as compared to those at 1 and 2 m. Most males were captured at 1100 hours and males remained in the vegetation under the trees throughout the day. Sweep netting revealed that conspecifics mate in the vegetation under orchard trees in the morning hours, and females move from the ground to the orchard canopy to oviposit at 1000 hours. Gas chromatographic-electroantennographic detection (GC-EAD) analyses indicated the presence of an electrophysiologically active compound in solid phase microextraction (SPME) effluvial collections and pheromone gland extractions from virgin females.
We examined the influence of habitat type (wooded, open, or edge) on behavioral responses of avian scavengers (Black Vultures [Coragyps atratus Bechstein], Turkey Vultures [Cathartes aura Linnaeus], American Crows [Corvus brachyrhynchos Brehm], and Blue Jays [Cyanocitta cristata Linnaeus]) at Gettysburg National Military Park (Gettysburg Park), PA, during winter of 2000 and 2001. We baited 18 sites once during January 2000–March 2000 and again during December 2000–March 2001 with the soft tissue of white-tailed deer (Odocoileus virginianus Zimmerman) for one 3-hour sampling period. We observed at least one scavenger species at bait areas (75-m radius of bait) in 97% of the 36 three-hour sampling periods; bait was eaten during 50% of the sampling periods. Turkey Vultures arrived first at bait areas most often, but American Crows were usually the species we observed eating the bait first. We observed Turkey Vultures most frequently (present in 14% of the 5-minute intervals) at bait areas, followed by American Crows (12%), Blue Jays (9%), and Black Vultures (6%). We observed Turkey Vultures, Black Vultures, and Blue Jays more commonly at bait areas in wooded habitat compared with those in open or edge habitat. In contrast, American Crows were more common at bait areas in open or edge habitat than in wooded habitat.
Turkey Vultures presumably were more vigilant (i.e., higher percentage of pausing) in wooded habitat than in open and edge habitat, Black Vultures were more vigilant in edge habitat, and American Crows were more vigilant in wooded and edge habitats than in open habitats. Because we observed Black Vultures more frequently at bait areas with Turkey Vultures than alone and Black Vultures arrived at bait areas later than the other species, Black Vultures seem to use the presence of other species, specifically Turkey Vultures, to find food.
Because wintering Willow Ptarmigan (Lagopus lagopus) display sex segregation with management implications, we obtained age and sex ratios from 340 hunter-harvested Willow Ptarmigan from 4 winter areas in Labrador: Javelin Mountain 1998–1999 (111 birds), Javelin Mountain 1999–2000 (96 birds), Lobstick Structure 1999–2000 (98 birds), and Mokami Hill 1998–1999 (35 birds). Those data illustrate a considerable age and sex segregation among wintering areas: Lobstick Structure birds were disproportionately male, 70% (46% adult male), Javelin Mountain birds were disproportionately female, 78% in 1998–1999 and 77% in 1999–2000. Mokami Hill, produced sex ratios between those of the other two areas: 69% female. Sex segregation on our wintering areas likely resulted from females dispersing farther from breeding areas than males. Because the climates of Javelin Mountain and Mokami Hill are successively warmer than that of Lobstick Structure, females may be selecting wintering areas that produce higher quality food than areas occupied by males. If Willow Ptarmigan are disproportionately taken from the Javelin Mountain area, then the substantial sex segregation on wintering areas suggests that hunter-harvest can suppress breeding success.
We describe the first observation of a male American Redstart (Setophaga ruticilla L.) brooding nestlings. Although this behavior has been documented in other North American members of the Family Parulidae, this is the first case in American Redstarts.