Annual variability in the radiocarbon age and source of dissolved CO2 in a peatland stream

Radiocarbon dating has the capacity to significantly improve our understanding of the aquatic carbon cycle. In this study we used a new passive sampler to measure the radiocarbon (14C) and stable carbon (δ13C) isotopic composition of dissolved CO2 for the first time in a peatland stream throughout a complete year (May 2010 – June 2011). The in-stream sampling system collected time-integrated samples of CO2 continuously over approximately one month periods. The rate of CO2 trapping was proportional to independently measured streamwater CO2 concentrations, demonstrating that passive samplers can be used to estimate the time-averaged dissolved CO2 concentration of streamwater. While there was little variation and no clear trend in δ13CO2 values (suggesting a consistent CO2 source), we found a clear temporal pattern in the 14C concentration of dissolved CO2. The 14C age of CO2 varied from 707±35 to 1210±39 years BP, with the youngest CO2 in the autumn and oldest in spring/early summer. Mean stream discharge and 14C content of dissolved CO2 were positively correlated. We suggest that the observed pattern in the 14C content of dissolved CO2 reflects changes in its origin, with older carbon derived from deeper parts of the peat profile contributing proportionally more gaseous carbon during periods of low stream flow

Modeling Avian Nest Survival in Program MARK

Understanding the factors infl uencing nesting success is a primary goal of many studies. To do this effectively, more advanced tools than Mayfi eld’s ad hoc estimator are needed. The recent development of a nest-survival model in program MARK provides a powerful and fl exible tool for the study of avian nest survival that can incorporate seasonal variation in survival and nest-specifi c covariates. We briefl y review the model and its development, illustrate how to include the effects of daily nest age and observer visits to nests, and conclude with an example analysis of Red-winged Blackbird (Agelaius phoeniceus) nest survival in Iowa. In this example, we found evidence for stagespecifi c differences in nest survival, seasonal patterns in nest survival that were best explained by a quadratic-time trend, and that survival differed between years. An exploration of several nestspecifi c covariates revealed that blackbird nest survival was positively affected by nest height, weakly affected by nest placement (nests placed in living vegetation may have experienced slightly higher survival), and unaffected by clutch size and within- and between-cell nest placement

Wildlife-habitat Relationships: Concepts and Applications

The study of wildlife populations often includes a habitat component, and understanding the functional relationship between a species and its habitat is challenging. The theoretical and analytical tools for doing so are many, and there are numerous texts that focus on but a fraction of this material. Morrison et al. provide a broad yet thorough overview of wildlifehabitat relationships in a well organized and easy to read book that includes background material, summarizes contemporary techniques for measuring these relationships, and offers links to management strategies

Atmosphere-soil-stream greenhouse gas fluxes from peatlands

The project aims to produce a complete inventory of greenhouse gas fluxes and emissions from a Scottish peatland. Carbon dioxide, methane and nitrous oxide emissions from the land surface (soil and vegetation) to the atmosphere, losses to streamwater and degassing will all be considered. The study is carried out at Auchencorth Moss, Midlothian, with intensive monitoring and measurements being made over a 2-year period, starting March 2006. The site consists of a patchwork of different vegetation communities including areas dominated by Calluna or Juncus, grassy hummocks and hollows and a narrow riparian zone again dominated by Juncus. GHG flux measurements will be made using chambers covering each vegetation type allowing for both a comparison between vegetation types and the subsequent scaling up to catchment level emissions. A flux tower on site provides further data on CO2 net exchange. In addition the concentrations of GHG in the soil are measured using gas permeable tubing. Other land based measurements will include water table depth, soil moisture, soil temperature and soil NO3, NH4 and DOC content. A datalogger is in place adjacent to the stream allowing for almost continuous measurements of stream temperature, conductivity and height; this data along with regular measurements of stream solute and dissolved gas concentrations will be used to estimate both stream gaseous emissions and lateral outputs. Routine measurements of carbon (DOC, DIC, POC, CO2 and CH4) and nitrogen (NO3, NH4, DON, N2O) will also be made along the stream length to measure spatial variability

Range Expansion of the Great-tailed Grackle in the 1900s

In 1900, the range of the Great-tailed Grackle extended north of the Mexican border only into Texas. Since then, it has expanded its range greatly. It now nests in 14 states and has strayed to an additional eight states and three Canadian provinces. Much of this expansion has occurred since 1960. Great-tails often stray far from their normal range, especially in spring. Most of these strays are single individuals. In states where they have nested, breeding birds typically reach the state a few years after the first reports of the species. Great-tailed Grackles do well in a variety of human altered habitats. Their range expansion in North America rivals that of the Cattle Egret both in its extent and as an example of a species thriving while living in close association with humans

The Influence of Habitat on Nest Survival of Snowy and Wilson\u27s Plovers in the Lower Laguna Madre Region of Texas

Snowy Plovers (Charadrius alexandrinus) and Wilson’s Plovers (Charadrius wilsonia) are two shorebird species that nest along the Gulf Coast of the US. We modeled the daily nest survival of both species in the lower Laguna Madre region of Texas during the 2003 and 2004 breeding seasons as a function of nest age, year, day in the season, maximum daily temperature, daily precipitation, and habitat features at three spatial scales (microhabitat, a 25-m radius of the nest, and landscape). Daily survival of Snowy Plover nests increased with nest age ( Age = 0.03, 95% confi dence limits were –0.01, 0.07, on a logit scale), but did not vary between years. Nests inland had substantially lower daily survival than nests on the coast ( Inland = –0.18, 95% confi dence limits were –1.03, 0.67, on a logit scale). The presence of a conspicuous object at the nest site increased daily nest survival. A quadratic trend occurred on the coeffi cient of variation (CV) for low vegetation (CV used as an index of low vegetation spatial heterogeneity) at the 25-m scale for Snowy Plover nests. Daily nest survival of Wilson’s Plovers was best explained by a combination of two habitat metrics at the microhabitat scale. Less vegetation at the immediate nest site increased daily survival ( Veg = –1.35, 95% confi dence limits were –2.28, –0.42, on a logit scale) while daily nest survival was higher for nests with lower contagion at the microhabitat scale ( Contagion = –0.87, 95% confi dence limits were –1.65, –0.10, on a logit scale). We found no evidence for yearly differences or an effect of weather on the daily nest survival of either species. Our results illustrate the role that selected habitat features play in the nest survival of Snowy and Wilson’s plovers and further our understanding of their nesting ecology. We anticipate that our results will assist in the identifi cation and protection of habitats critical to breeding populations of these and other shorebird species

Egg crypsis in a ground-nesting shorebird influences nest survival

Coloration of exposed eggs of ground-nesting birds is thought to reduce predation, with camouflaged eggs that more closely match the area around the nest having greater survival. We tested this hypothesis using digital photographs of 374 Mountain Plover (Charadrius montanus) nests and the substrate surrounding each nest to produce covariates in nest survival models. Covariates included values representing the difference between the color of the eggs and that of the substrate, the average egg and substrate colors, and variation in both egg and substrate color. Nest survival decreased as the difference between the color of the eggs and substrate increased (accounted for by two different methods of quantifying color and increased with increasing variability in substrate color, although after model-averaging these effects were not well-supported. Model-averaged estimates of daily nest survival ranged from 0.90 to 0.98 (unconditional SEs from 0.004 to 0.129). Our results support the egg crypsis hypothesis because eggs that closely match their surroundings have greater survival

Density and Abundance of Mountain Plovers in Northeastern Montana

Estimates of local abundance for declining species provide important information necessary for conservation measures. We estimated the density and abundance of Mountain Plover (Charadrius montanus) in Phillips and Valley counties in north-central Montana in 2004 using distance sampling methodology. Sampling efforts were stratified to include active prairie dog (Cynomys sp.) colonies, an Area of Critical Environmental Concern (ACEC) specifically established for Mountain Plover, and all other habitats. The density of plovers was greatest on prairie dog colonies (7.20 ± 0.42 [SE] plovers/km2) and much lower on both the ACEC (1.60 ± 0.31 plovers/km2), and all other habitats (0.07 ± 0.01 plovers/km2). An estimated 1,028 (95% CI = 903–1,153) plovers inhabited this region in 2004, most (74%) on prairie dog colonies. Our results highlight the importance of prairie dog colonies to plovers in this region and suggest that as much as 10% of their continental population may breed in north-central Montana

Goodbye, Mother

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