An index of reproductive activity provides an accurate estimate of the reproductive success of Palm Warblers

ABSTRACT.   Various indices of reproductive activity (IRA) have been used to estimate the reproductive success of songbirds. However, the performance of IRAs varies among systems examined, and this approach still requires more effort than standard surveys. We tested the accuracy of an IRA in a survey of birds nesting in bogs in eastern New Brunswick, Canada. We compared an IRA obtained through point counts with playbacks ("extensive" IRA) to another IRA obtained through intensive searches for evidence of breeding ("intensive" IRA) by Palm Warblers ( Dendroica palmarum ). Both the extensive IRA and associated abundance index were correlated with the intensive IRA, the former correlation being stronger. However, the extensive IRA tended to underestimate the status of breeding birds and overestimate the status of nonreproducing individuals that behaved more conspicuously. Nonetheless, the extensive IRA obtained using song playbacks represents a time-efficient alternative to intensive nest monitoring when estimating habitat quality at the scale of small (0.78 ha) study plots.     

Effects of exotic <Emphasis Type="Italic">Spartina alterniflora</Emphasis> on the habitat patch associations of breeding saltmarsh birds at Chongming Dongtan in the Yangtze River estuary,China

Smooth cordgrass (Spartina alterniflora) is one of the most invasive exotic plants of saltmarshes worldwide. To understand the effects of smooth cordgrass invasion on the habitat use and selection by breeding saltmarsh birds, we compared species number and abundance of breeding birds in native reed (Phragmites australis) and smooth cordgrass-invaded habitats (reed-cordgrass mixed habitats and cordgrass monocultures) at Chongming Dongtan in the Yangtze River estuary, China. We further examined the similarity of bird communities in different habitats and habitat selection by dominant bird species. For saltmarsh generalists, species number and abundance did not differ among the habitats. For saltmarsh specialists, species number and abundance did not differ in reed monocultures and reed-cordgrass mixed habitats but were significantly lower in cordgrass monocultures than in reed monocultures and reed-cordgrass mixed habitats. ANOSIM indicated that the difference in bird communities was larger between cordgrass monocultures and the habitats with reed than between the habitats with reed. The saltmarsh specialists preferred reed monocultures, while saltmarsh generalists avoided reed monocultures. Most species indicated no selection (neither preferred nor avoided) on reed-cordgrass mixed habitats, and no species preferred the cordgrass monocultures. The use of cordgrass monocultures by the common saltmarsh birds was negatively related to their body size. This study suggests that the spread of exotic smooth cordgrass has greatly affected the species composition and structure of local bird communities and has been especially disadvantageous to the saltmarsh specialists.     

Abundance of Snowy and Wilson's Plovers in the lower Laguna Madre region of Texas

ABSTRACT.   Snowy Plovers ( Charadrius alexandrinus ) and Wilson's Plovers ( C. wilsonia ) are shorebird species of increasing conservation concern, with populations apparently declining in North America. However, estimates of current populations are needed before initiating long-term monitoring or planning. In 2004, we estimated abundance of breeding Snowy and Wilson's plovers in the lower Laguna Madre region of Texas using occupancy abundance estimation. We made repeated visits to survey plots from April to June, recording the number of adults of both species observed and the amount of suitable breeding habitat within each plot. We considered Bayesian occupancy abundance models with and without habitat covariates to explain the abundance of both species. For both Snowy and Wilson's plovers, the number of birds counted in each plot was influenced by the amount of suitable breeding habitat within the plot (Snowy Plover α_habitat= 0.52, SD = 0.10, 95% CI = 0.33–0.71; Wilson's Plover α_habitat= 0.48, SD = 0.12, 95% CI = 0.24–0.71). Using the habitat covariate models for each species, we estimated that 416 adult Snowy Plovers (95% CI = 394–438) and 279 adult Wilson's Plovers (95% CI = 262–296) were present in our study area. Our results illustrate the use of a relatively new method for abundance estimation, and indicate that the lower Laguna Madre region of Texas is an important breeding area for both Snowy and Wilson's plovers. Given the documented and suspected population declines for Snowy and Wilson's plovers, we recommend protection of their breeding habitats along the coast of Texas from development and degradation resulting from unregulated use.     

Estimating breeding season abundance of golden-cheeked warblers in Texas,USA

Population abundance estimates using predictive models are important for describing habitat use and responses to population-level impacts, evaluating conservation status of a species, and for establishing monitoring programs. The golden-cheeked warbler (Setophaga chrysoparia) is a neotropical migratory bird that was listed as federally endangered in 1990 because of threats related to loss and fragmentation of its woodland habitat. Since listing, abundance estimates for the species have mainly relied on localized population studies on public lands and qualitative-based methods. Our goal was to estimate breeding population size of male warblers using a predictive model based on metrics for patches of woodland habitat throughout the species' breeding range. We first conducted occupancy surveys to determine range-wide distribution. We then conducted standard point-count surveys on a subset of the initial sampling locations to estimate density of males. Mean observed patch-specific density was 0.23 males/ha (95% CI = 0.197–0.252, n = 301). We modeled the relationship between patch-specific density of males and woodland patch characteristics (size and landscape composition) and predicted patch occupancy. The probability of patch occupancy, derived from a model that used patch size and landscape composition as predictor variables while addressing effects of spatial relatedness, best predicted patch-specific density. We predicted patch-specific densities as a function of occupancy probability and estimated abundance of male warblers across 63,616 woodland patches accounting for 1.678 million ha of potential warbler habitat. Using a Monte Carlo simulation, our approach yielded a range-wide male warbler population estimate of 263,339 (95% CI: 223,927–302,620). Our results provide the first abundance estimate using habitat and count data from a sampling design focused on range-wide inference. Managers can use the resulting model as a tool to support conservation planning and guide recovery efforts. © 2012 The Wildlife Society.     

Can spatial and temporal food variability explain the winter foraging movements of a threatened saltmarsh insectivore?

The white‐fronted chat (Epthianura albifrons) is a small, insectivorous passerine that is threatened with extinction in the north‐eastern part of its range, partially due to loss and degradation of its saltmarsh habitat. Food availability is a potential limiting factor for the disjunct populations that survive in saltmarsh refugia, surrounded by urbanized land, because the anthropogenic matrix reduces the capacity of birds to commute to alternative grassland habitat to exploit temporary insect outbreaks. This limitation is likely to be exacerbated during the winter months when local arthropod abundance in saltmarsh is reduced. This study measured temporal and spatial variation in the abundance of saltmarsh arthropods to determine whether patch switching by foraging flocks can be explained by variation in food availability. Arthropods in the size range known to be important in the diet of white‐fronted chats were vacuum‐sampled from six patches within a continuous area of Sarcocornia‐dominated saltmarsh over a four‐month period. The location of foraging birds was recorded during the same period. Despite superficial similarity in vegetation composition and structure, there was significant variation in arthropod biomass among sites through time, such that the patches with the highest food abundance changed from month to month. There was little evidence, however, to suggest that white‐fronted chats foraged in saltmarsh patches with the highest overall food abundance. During the course of the study, birds were discovered flying 2 km from the saltmarsh to a development site where they foraged in weedy grassland. Arthropod samples collected from this site contained an extremely high abundance of Hemiptera and Neuroptera larvae, supporting previous research indicating that white‐fronted chats forage on irruptions of particular arthropod taxa. These findings indicate that food abundance is unlikely to be the main determinant of foraging site selection within saltmarsh, but highlights the potential importance of alternative foraging habitat types for this species.     

Predicting the distribution of a suitable habitat for the white stork in Southern Sweden: identifying priority areas for reintroduction and habitat restoration

The loss of wetlands and semi-natural grasslands throughout much of Europe has led to a historic decline of species associated with these habitats. The reinstatement of these habitats, however, requires spatially explicit predictions of the most suitable sites for restoration, to maximize the ecological benefit per unit effort. One species that demonstrates such declines is the white stork Ciconia ciconia , and the restoration of habitat for this flagship species is likely to benefit a suite of other wetland and grassland biota. Storks are also being reintroduced into southern Sweden and elsewhere, and the a priori identification of suitable sites for reintroduction will greatly improve the success of such programmes. Here a simple predictive habitat-use model was developed, where only a small but reliable presence-only dataset was available. The model is based on the extent and relative soil moisture of semi-natural pastures, the extent of wetlands and the extent of hayfields in southern Sweden. Here the model was used to predict the current extent of stork habitat that is suitable for successful breeding, and the extent of habitat that would become suitable with moderate habitat restoration. The habitat model identifies all 10 occupied nesting sites where breeding is currently successful. It also identifies ∼300 km² of habitat that is predicted to be suitable stork habitat, but that is presently unused; these sites were identified as potential areas for stork reintroduction. The model also identifies over 100 areas where moderate habitat restoration is predicted to have a disproportionate effect (relative to the restoration effort) on the area of suitable habitat for storks; these sites were identified as priorities for habitat restoration. By identifying areas for reintroduction and restoration, such habitat suitability models have the potential to maximize the effectiveness of such conservation programmes.     

Seasonal Abundance and Species Richness of Birds in Common Reed Habitats in Lake Erie

Abstract: Common reed (Phragmites australis) forms dense stands with deep layers of residual organic matter that negatively affects plant diversity and possibly habitat use by wetland birds. We sought to determine whether seasonal relative abundance and species richness of birds varied among 3 habitat types in Great Lakes coastal wetland complexes recently invaded by common reed. We used fixed-distance point counts to determine species relative abundances and species richness in edge and interior locales within common reed, cattail (Typha spp.), and meadow marsh habitats of various sizes during 2 summers (2001 and 2002) and 1 autumn (2001) at Long Point, Lake Erie, Ontario, Canada. We found that total relative abundance and species richness of birds were greater in common reed habitat compared to cattail or meadow marsh habitats. However, we also found that relative abundance of marsh-nesting birds was greater in meadow marsh habitat than in cattail and common reed during summer. Lastly, we found that, irrespective of habitat type, habitat edges had higher total relative abundance and species richness of birds than did habitat interiors. Our results show that common reed provides suitable habitat for a diversity of landbirds during summer and autumn but only limited habitat for many marsh-nesting birds during summer. Based on these results, we recommend restoration of meadow marsh habitat through reduction of common reed in Great Lakes wetlands where providing habitat for breeding marsh-nesting birds is an objective. Managers also might consider reducing the size of nonnative common reed stands to increase edge effect and use by birds, possibly including wetland birds.     

The numerical response of breeding Northern Saw-whet Owls Aegolius acadicus suggests nomadism

We used a 13-year time series of abundance estimates of breeding Northern Saw-whet Owls (Aegolius acadicus), and of small mammals from central Ontario, Canada, to assess the numerical response of the owls to small-mammal prey species. We found that the finite rate of increase of breeding owls was directly related to estimates of red-backed vole (Myodes gapperi) abundance. Thus, it appeared that the owls were nomadic, and made decisions about where to breed based on vole supply. The owls showed a much weaker response to deer mouse (Peromyscus maniculatus) abundance. Across all years, 55% of variation in owl rate of increase could be uniquely attributed to vole abundance, whereas only 3% could be attributed to mouse abundance. Consistent with the model of nomadism, there was only a weak relationship between the proportion of hatch-year owls caught at fall banding stations, and small-mammal abundance. Instead, it appeared that Northern Saw-whet Owls avoided years of widespread reproductive failure through the nomadic strategy of selecting breeding sites based on vole supply.     

Fishes of a subtropical Australian saltmarsh and their predation upon mosquitoes

Synopsis The fishes occurring in a subtropical Australian saltmarsh were studied from January to December 1984 to determine the seasonal abundance and feeding of the most common species. Wide variations in pool water levels and salinity were recorded. Eight species of fish were collected, four of which are of economic importance to fisheries. Three taxa, Gambusia affinis, Pseudomugil signifer, and gobiids predominated in terms of abundance and occurrence. The abundance of fishes fluctuated markedly on a seasonal basis with few fish being taken in winter and spring (June–November) when pool water levels were low. Diets of the most common species were similar with terrestrial foods forming an important component of all diets. Feeding activity was highest in summer (December to February) when mosquito larvae, copepods, and larval coleopterans formed a large proportion of the fishes' diets. Results from the present study indicate that fish important to commercial fisheries rarely utilise the upper littoral saltmarsh habitat and that resident fishes are unlikely to effectively control mosquito larvae in saltmarsh.     

The reproductive endocrinology and behavior of Vancouver Island marmot (Marmota vancouverensis)

The Vancouver Island marmot (Marmota vancouverensis; VIM) is one of North America's most endangered species with fewer than 150 individuals remaining in the wild. A captive breeding program was established across four facilities in Canada as an insurance population and source of animals for reintroduction to the wild. The purpose of this study was to gather information about the basic reproductive biology and behavior of this species, which is essential to improve captive breeding programs. Regular fecal samples were obtained from adult female (n = 14) and male (n = 10) marmots, 2 years of age and older, over 1-3 breeding seasons (2-3 months duration posthibernation) for steroid hormone analysis. Enzyme immunoassays were validated for quantifying fecal testosterone metabolite concentrations for males, and fecal estrogen and progesterone metabolite concentrations for females. Results indicated that fecal progesterone metabolite concentrations can be used to monitor ovulation and pregnancy. Behavioral monitoring through infrared video surveillance was conducted in four breeding pairs over a 2-year period (n = 7 behavioral profiles). Breeding behaviors correlated strongly with changes in reproductive endocrine profiles. A high frequency of play behavior or "wrestling" was observed in conjunction with breeding activity before an elevation in progesterone metabolite concentrations. Impending parturition was associated with increased aggression and exclusion of the male from the maternal nestbox as well as an increase in nesting activity. Observational data combined with hormonal analysis suggest that female VIMs are induced ovulators and that multiple breeding attempts may be required for ovulation and conception. Gestation appears to be approximately 34 days from peak breeding activity (32 days from estimated ovulation). Fecal testosterone concentrations suggest that testicular activity is seasonal with the reproductive activity occurring immediately posthibernation. Monitoring breeding behavior is a useful means of indicating estrus, conception and pregnancy, which can also be supported by the hormonal analysis of daily fecal samples of individual animals.     

Effects of local and landscape-scale habitat variables on abundance and reproductive success of wetland birds

Both local and landscape-scale habitat variables influence the abundance of wetland breeding birds. Few studies, however, simultaneously assess the effects of habitat variables at multiple spatial scales or consider effects on reproductive success. Therefore, we examined the effects of wetland and landscape-scale habitat variables on the abundance of nine breeding bird species and the effects of nest, wetland, or landscape-scale habitat variables on the nest success, clutch size, or number of fledglings of four species at 15 cattail (Typha sp.)-dominated wetlands in an agricultural region around Peterborough, Ontario, Canada. The abundance of Least Bittern (Ixobrychus exilis), Common Moorhen (Gallinula chloropus), and Marsh Wren (Cistothorus palustris) increased as wetland water depth increased; the abundance of Common Moorhen and Marsh Wren increased as wetland size increased; and the abundance of Marsh Wren increased as the amount of wetland in the surrounding landscape increased. Red-winged Blackbird (Agelaius phoeniceus) nest success decreased as nest cover increased. Clutch sizes were uninfluenced by the habitat variables that we considered. The number of Red-winged Blackbird fledglings per successful nest increased as wetland size increased and as the amount of wetland in the surrounding landscape increased. We speculate that food limitation in small wetlands may be responsible for the pattern in Red-winged Blackbird fledging success. The abundance and nest success of Virginia Rail (Rallus limicola) and Sora (Porzana carolina) were uninfluenced by the habitat variables we considered. Future research should consider mate attraction and productivity in relation to local and landscape-scale habitat variables for these and other secretive species. Our study suggests that wetland conservation will be most effective if it considers habitat variables at multiple spatial scales.     

Effect of beta-carotene administration on reproductive function of horse and pony mares

The objective of this study was to determine whether supplemental beta-carotene would influence reproductive function in mares maintained on spring and summer pastures and to characterize plasma carotene concentrations during the estrous cycle. Carotene concentrations in plasma did not vary with day of estrous cycle (P = 0.7455). Mares receiving every other day injections of beta-carotene (400 mg; n = 4) or saline (10 ml; n = 4) during proestrus/estrus did not differ in plasma estradiol (E(2)) concentrations (P = 0.6313), follicle development (P = 0.8068), or plasma progesterone (P(4)) concentrations during the following diestrus (P = 0.4954). Moreover, no differences in plasma P(4) concentrations (P = 0.9047) were detected between mares receiving every other day injections of beta-carotene (400 mg; n = 4) or saline (10 ml; n = 4) during diestrus. However, administration of beta-carotene raised plasma carotene concentrations relative to controls when injected during proestrus/estrus (P = 0.0096) and diestrus (P = 0.0099). Pregnancy rates (P = 0.4900) and number of cycles required for pregnancy (P = 0.2880) were similar for mares administered injections of saline (10 ml; n = 37), beta-carotene (400 mg; n = 37), vitamin A (160,000 IU; n = 38), or vitamin A + beta-carotene (160,000 IU + 400 mg; n = 43), on the first or second day of estrus and on the day of breeding. Therefore, these results collectively suggest that supplemental beta-carotene does not affect the reproductive function of mares fed adequate dietary carotene. Whether supplemental beta-carotene would enhance reproductive function in mares on low carotene diets warrants further investigation.     

Temporal variability of stream bioassessments using benthic macroinvertebrates

1. When using benthic macroinvertebrate communities for bioassessment, temporal variation may influence judgement as to whether or not a site is degraded.
2. In a survey of sixteen reference and sixteen test sites in the upper Thames River catchment area (UTRCA) in south-western Ontario, Canada, consistent differences between summer and winter samples were found for taxon richness (increase; P = 0.06) and the Family Biotic Index (decrease; P = 0.11). A bioassessment based on these results would indicate better water quality in the same streams in winter relative to summer. No consistent pattern of seasonal difference was detected for Simpson's Diversity and Equitability, or percentage Dominant Taxon.
3. The Reference Condition Approach to bioassessment uses predictive modelling to explain variation in reference communities with the environmental conditions at these sites as predictors. The community at a test site is compared with that predicted by the model. Several predictive models were constructed using simple geographic and habitat characteristics (i.e. catchment area, distance to source, stream width, substrate and habitat diversity) as predictors. By including season of sampling in the models, we increased their predictive power and the ability of the bioassessment to detect degradation. The best results were achieved when separate predictive models were built for each sampling season.     

Spatial and seasonal trends of a natural population of Biomphalaria occidentalis in northeastern Argentina.

This study aims to analyze the age structure of a population of Biomphalaria occidentalis on a pond of Riachuelo river basin, which is one of the three most important Middle Paraná river affluents in Corrientes province. Samples were drawn from three stations, where spatial and temporal numerical variations of the snail, as well as its relation with different environmental parameters, mainly temperature, rainfall, pH and conductivity, were analyzed. Snail abundance is given in number of individuals/hour. The differences between the three sampling stations, estimated by nonparametric tests, was nonsignificant. A relative scale to the greatest shell diameter was employed to build the age pyramids. Temporal fluctuations of snail abundance correlated negatively with the highest monthly accumulated temperatures (P < 0.05). Although different floristic compositions were observed at the three stations, no significant numerical variations were detected in B. occidentalis spatial distribution. Reproductive activity took place between March-April and November with overlapping cohort system. During summer (December-February) mortality increased along with temperature and reproductive activity was not evident.     

Potential Role of Spruce Budworm in Range-Wide Decline of Canada Warbler

ABSTRACT The Canada warbler (Wilsonia canadensis) is one of many common neotropical migrants whose populations are in decline across their range. Influences of habitat loss and degradation on breeding or wintering grounds have been postulated as possible causes, but few empirical data exist to support a specific cause. Based on previous studies linking abundances of Canada warbler and spruce budworm (Choristoneura fumiferana), we hypothesized that the Canada warbler may be influenced by a persistent decline in spruce budworm throughout the bird's breeding range, a hypothesis that has received little attention. This hypothesis makes 5 predictions: 1) budworm outbreaks and warbler detections should be spatially and temporally coincident; 2) the relationship between Canada warbler and spruce budworm outbreaks should be similar to relationships for other warblers known to be spruce budworm associates; 3) the relationship should be stronger than for warblers lacking an association with spruce budworm; 4) because temporal trends of both spruce budworm and Canada warblers have varied throughout Canadian provinces, declines in Canada warblers should be seen only in provinces where spruce budworm also declined; and 5) variation in Canada warbler abundance should reflect variation in supply of preferred habitat for the spruce budworm if habitat rather than budworm abundance is the key. Our analyses supported predictions 1–4, suggesting that Canada warbler may be even more closely associated with spruce budworm than are known associated species, a phenomenon noted in the literature but previously unexplained. Prediction 5 was not supported, because budworm habitat (area of mature and older balsam fir [Abies balsamea] and white spruce [Picea glauca]) remained constant in Ontario while warbler abundance declined. Although the correlative nature of these results precludes inference of a causal relationship between the declines of the Canada warbler and spruce budworm, we postulate that potential links may exist directly, where spruce budworm outbreaks provide elevated levels of insect prey items for breeding Canada warblers, or indirectly through changes in forest structure and composition following outbreaks. These results have implications when considering long-term trends in Canada warbler populations, because it may be impossible to alter population trends for species linked to the timing and magnitude of spruce budworm outbreaks.     

Fire Elicits an Adaptive Reproductive Strategy Shift from Host Plant Quantity to Quality in a Capital Breeding Species

Capital breeding species, those that do not acquire resources over their reproductive period, are hypothesized to have more flexible reproductive strategies than income breeding species, enabling the former to better cope with environmental changes. Yet, empirical study of this life history attribute in a changing environment is rare. Hemileuca eglanterina (Saturniidae), a strict capital breeding, day-flying moth, should employ a different reproductive strategy to exploit temporary increases in host plant nutrient quality following fire. In wetlands, where one half was burned and the other left unburned, the number of eggs/clutch was positively correlated with host plant abundance in the absence of fire, suggesting that H. eglanterina uses a resource abundance matching reproductive strategy by default. However, following fire, H. eglanterina laid greater numbers of eggs/clutch and did not adjust clutch size to host plant abundance, appearing to shift to a host plant quality based reproductive strategy. Coinciding with the fire-induced shift in reproductive strategy, host plants from burned habitat contained a greater proportion of N-containing compounds in their foliage than plants from unburned habitat, and larvae fed only leaves from the burned habitat had significantly greater survival than siblings fed unburned foliage. These results suggest the shift in reproductive strategy by H. eglanterina following fire was adaptive and that capital breeding species can cope with sudden environmental changes via alternative reproductive strategies.     

Habitat diversity and fish assemblages in an African river basin (Nyagui River, Zimbabwe)

Little is known about the ecology of stream fishes in Zimbabwe and this study investigated fish communities in the Nyagui River basin and is one of the first to examine the relationship between fish assemblages and habitat diversity in Zimbabwe. Fourteen sampling stations were, for convenience, divided into three groups; upper (>1400 m above sea level), middle (1000–14000 m) and lower stations (<1000 m). A total of 24 species were collected, four of which were introduced, and the species composition differed according to the location of the stations. Species that favoured running water and/or rocks were generally absent from the upper stations, reflecting the fact that they were mostly sandy‐bottomed and still. Diversity and relative abundance increased in the mid‐ and low‐altitude stations, which were rockier and faster flowing. Both species diversity and relative abundance increased with the catchment area above each station, which was attributed to increased habitat diversity in larger streams. This view was supported by a strong correlation between habitat diversity and catchment area, and between habitat diversity and species richness and relative abundance. At present, the Nyagui system is relatively unregulated but the Kunzvi Dam, presently under construction, will change this situation and species diversity is likely to decrease owing to the loss of rheophilic species while other groups, notably cichlids and introduced species will increase.     

Odonates as biological indicators of grazing effects on Canadian prairie wetlands

Abstract.  1. Aquatic macro-invertebrates have frequently been used as biological indicators in lotic environments but much less commonly so in lentic habitats. Dragonflies and damselflies (Order Odonata) satisfy most selection criteria for lentic bioindicators of grazing impacts.
2. Intensive cattle grazing affects most of the Canadian prairie pothole region but the effects of grazing on wetlands are poorly understood.
3. Here the vegetation structure and invertebrate community composition of 27 prairie potholes in Alberta, Canada were studied and compared. Wetlands were evenly divided into three treatments of different grazing regimes.
4. Removal of emergent vegetation by cattle grazing decreased odonate abundance and reproductive effort. Shorter Scirpus acutus stems resulted in significantly fewer damselflies (Suborder Zygoptera) and lower reproductive efforts.
5. Overall odonate diversity was affected by the height of key plant species, highlighting the importance of the vegetation structure of both emergent vegetation for breeding and adjacent upland vegetation for nocturnal roosts. Wetland vegetation structure was more important than vegetation composition to the life history of odonates.
6. Wetland water quality parameters of nitrogen, phosphorus, total dissolved solids (TDS), and chlorophyll-a concentration did not change due to the presence of grazing cattle at wetlands so water quality influences were rejected as mechanisms of change.
7. Larval odonate diversity and abundance was positively correlated with overall aquatic macro-invertebrate diversity and abundance, hence it was concluded that the larval odonate community can be an accurate bioindicator of intactness and diversity of overall aquatic macro-invertebrate communities in Canadian prairie wetlands.     

Nest trampling and ground nesting birds: Quantifying temporal and spatial overlap between cattle activity and breeding redshank

Conservation grazing for breeding birds needs to balance the positive effects on vegetation structure and negative effects of nest trampling. In the UK, populations of Common redshank Tringa totanus breeding on saltmarshes declined by >50% between 1985 and 2011. These declines have been linked to changes in grazing management. The highest breeding densities of redshank on saltmarshes are found in lightly grazed areas. Conservation initiatives have encouraged low‐intensity grazing at <1 cattle/ha, but even these levels of grazing can result in high levels of nest trampling. If livestock distribution is not spatially or temporally homogenous but concentrated where and when redshank breed, rates of nest trampling may be much higher than expected based on livestock density alone. By GPS tracking cattle on saltmarshes and monitoring trampling of dummy nests, this study quantified (i) the spatial and temporal distribution of cattle in relation to the distribution of redshank nesting habitats and (ii) trampling rates of dummy nests. The distribution of livestock was highly variable depending on both time in the season and the saltmarsh under study, with cattle using between 3% and 42% of the saltmarsh extent and spending most their time on higher elevation habitat within 500 m of the sea wall, but moving further onto the saltmarsh as the season progressed. Breeding redshank also nest on these higher elevation zones, and this breeding coincides with the early period of grazing. Probability of nest trampling was correlated to livestock density and was up to six times higher in the areas where redshank breed. This overlap in both space and time of the habitat use of cattle and redshank means that the trampling probability of a nest can be much higher than would be expected based on standard measures of cattle density. Synthesis and applications: Because saltmarsh grazing is required to maintain a favorable vegetation structure for redshank breeding, grazing management should aim to keep livestock away from redshank nesting habitat between mid‐April and mid‐July when nests are active, through delaying the onset of grazing or introducing a rotational grazing system.     

Intertidal ecology and potential power impacts, Bay of Fundy, Canada

A large-scale tidal power project in the upper reaches of the Bay of Fundy would cause major changes in the tidal elevations of the headpond which would have a pronounced effect on intertidal ecology. The new mean low water level would be, on average, slightly above the present mean sea level whilst the new mean high water level would drop about 0.7 m. This would result in a much compressed intertidal zone. Mud and sand flats, below the present mean sea level, would be converted to sub-tidal habitat, whilst the high saltmarsh, flooded at present only on the highest spring tides, would become colonized by terrestrial vegetation. There would be major shifts in the relative importance of primary production by saltmarshes, intertidal microalgae and phytopiankton, but overall, it is likely that production would increase. Changes in both primary food sources and habitat area would affect the abundance of intertidal invertebrate organisms and the fish and migratory shorebirds that feed upon them.