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Conservation of obligate grassland species requires not only the protection of a sufficiently large area of habitat but also the availability of necessary vegetation characteristics for particular species. As a result land managers must understand which habitat characteristics are important for their target species. To identify the habitat associations of eight species of grassland birds, we conducted bird and vegetation surveys on 66 grassland habitat patches in southwestern Minnesota in 2013 and 2014. Species of interest included sedge wren (Cistothorus platensis), Savannah sparrow (Passerculus sandwichensis), grasshopper sparrow (Ammodramus savannarum), Henslow's sparrow (Ammodramus henslowii), dickcissel (Spiza americana), bobolink (Dolichonyx oryzivorus), and western meadowlark (Sturnella neglecta). We calculated correlation coefficients between vegetation variables and species density as measures of linear association. We assessed curvilinear relationships with loess plots. We found grassland birds on 95.5% of surveyed sites, indicating remnant prairie in southwestern Minnesota is used by grassland birds. In general individual species showed different patterns of association and most species were tolerant of a wide variety of habitat conditions. The most consistent pattern was a negative association with both the quantity and proximity of trees. Our findings that individual species have different habitat preferences suggest that prairie resource managers may need to coordinate management efforts in order to create a mosaic of habitat types to support multiple species, though tree control will be an important and ongoing management activity at the individual site level.
Forests in the eastern United States have become fragmented by urban development and agriculture, creating a landscape of remnant forest patches. Many bird species rely on these fragments for breeding habitat, but habitat selection in these patches is not well-understood. Our objective was to examine the effects of forest structure, native plants, and invertebrate biomass on the occupancy of an assemblage of common Eastern songbird species in suburban forest fragments. We collected data at 98 plots in remnant forest patches in Delaware and Maryland. Avian point counts were conducted three times per season between 15 May–7 August 2009–2010. We estimated occupancy probability, while accounting for imperfect detection, for nine common songbird species in order to understand how they are influenced by invertebrate biomass and vegetation characteristics. We ranked competing models using Akaike Information Criteria (AIC). Occupancy of six of our 10 candidate species was affected by forest structure, native plant density, or invertebrate biomass. Species we identified to have occupancy relationships with forest structure variables in suburban forest fragments appear to align well with habitat relationships that have been previously identified for the species in more forested areas. This supports that managing for structural characteristics associated with these species in more heavily forested areas could improve habitat quality for these species in suburban forest fragments as well. Occupancy of only one species we examined was related to native plants, suggesting vegetation structure, rather than composition, was a more important factor in occupancy.
Home range size, location, and movements between home ranges may differ markedly within species. Some populations of Bald Eagles breed in summer and move south in winter, whereas others breed in winter and move north in summer, while even others stay in the same area all year. We studied winter breeding and summer nonbreeding home range sizes and locations for 10 Bald Eagles (five adults, three subadults, and two subadults that became adults) captured in Louisiana and tracked with GPS satellite transmitters. Individuals were tracked from 2012–2014, during which, all spent the winter breeding season in Louisiana and all migrated north to Canada for at least one summer nonbreeding season. Most held clearly defined home ranges, which varied from 19.7–2368.3 km2, with no significant difference between adults and subadults, winter breeding and summer nonbreeding ranges, year, or their interactions. All nesting home ranges were less than 66 km2 and, on average, nonnesting home rages were 730.3 ± 183.4 km2; however, there was no significant difference in home range size between nesting and nonnesting adults on winter breeding grounds. Individuals exhibited a high degree of fidelity to winter breeding home ranges and relatively high fidelity to summer nonbreeding home ranges. Our baseline estimates of home range size and fidelity for adults and subadults on their winter breeding and summer nonbreeding areas provides insight into the spatial requirements of Bald Eagles, whereas locations and movements between these areas provides insight into intraspecific variation among populations.
Geomys pinetis (Southeastern pocket gopher) is a fossorial rodent historically associated with Pinus palustris (longleaf pine) communities. Conversion and fragmentation of longleaf pine communities have reduced quality and quantity of southeastern pocket gopher habitat. It is therefore important to determine characteristics of suitable habitat for future conservation efforts focusing on maintaining or restoring appropriate habitat conditions. We quantified understory vegetation structure (i.e., ground cover categories) and soil characteristics (i.e., soil texture, pH, nitrogen, and carbon at multiple depths) in areas with and without pocket gopher activity. We evaluated a suite of models to determine whether understory vegetation structure, soil characteristics, or a combination of vegetation and soil characteristics were better predictors of gopher presence. Soil characteristics predicted pocket gopher presence better than understory vegetation structure with the best overall model combining percent clay, percent silt, pH, nitrogen, and carbon. Percent clay, percent silt, pH, and nitrogen were the most informative predictors. We suggest vegetation variables were of lesser importance because suitable understory vegetation was common across our study site. Our data suggest presence of suitable understory vegetation structure may be insufficient for southeastern pocket gopher restoration if soil characteristics are unsuitable.
In mammals, expression of certain melanocortin receptor ligands is correlated with both dark pigmentation and increased stress resistance and higher levels of aggression. Though many studies of captive and laboratory animals have explored this pleiotropic interaction, relatively few studies of animal behavior have occurred in free-living wild animals. This playback study focused on the antipredator behavior differences between melanistic and gray morphs of eastern gray squirrels (Sciurus carolinensis) in Hiram, Ohio. Vigilance, tail flagging, freezing, and escape behaviors were recorded in response to digital playback of an American robin call, a chickadee call, a car alarm, a buzzer, or one of two different red-tailed hawk calls. All squirrels exhibited increased antipredator behavior after hearing increasingly threatening stimuli. Consistent with prior findings in other species with color polymorphism, gray morphs were more likely to escape after hearing a threatening call. A growing body of evidence indicates it is possible to study pleiotropic effects of genes in free living animals.
Conservation and management of rare fishes relies on managers having the most informed understanding of the underlying ecology of the species under investigation. Cisco (Coregonus artedi), a species of conservation concern, is a cold-water pelagic fish that is notoriously variable in morphometry and life history. Published reports indicate, at spawning time, Cisco in great lakes may migrate into or through large rivers, whereas those in small lakes move inshore. Nonetheless, during a sampling trip to Follensby Pond, a 393 ha lake in the Adirondack Mountains, New York, we observed gravid Cisco swimming over an outlet sill from a narrow shallow stream and into the lake. We opportunistically dip-netted a small subsample of 11 individuals entering the lake from the stream (three female, eight male) and compared them to fish captured between 2013 and 2015 with gillnets in the lake. Stream-captured Cisco were considerably larger than lake-captured individuals at a given age, had significantly larger asymptotic length, and were present only as mature individuals between age of 3 and age 5. These results could suggest either Cisco are migrating from a nearby lake to spawn in Follensby Pond, or that a distinct morphotype of Cisco from Follensby Pond migrates out to the stream and then back in at spawning time. Our results appear to complement a handful of other cases in which Cisco spawning migrations have been documented and to provide the first evidence for such behavior in a small inland lake.
Grazers may increase grassland plant species diversity through mechanisms such as selective consumption of graminoids resulting in release from competition in subordinate forb species, or the enhancement of small-scale habitat heterogeneity. This study tested the hypothesis bison on tallgrass prairie reduce local plant competition and increase the growth, reproduction, abundance, and diversity of forbs. In addition, because grazers, fire, and other drivers result in high spatio-temporal variation in limiting plant resources in tallgrass prairie, we tested the hypothesis that prairie forbs show high phenotypic plasticity in life history traits in response to large grazers.
The growth, reproduction, biomass allocation, and abundances of six common perennial forb species, and estimates of local neighborhood and physical environmental factors were compared in replicate tallgrass prairie sites with and without bison. Greater light availability and percent bare ground; and lower grass canopy density, height, and cover in habitats with bison indicated reduced aboveground plant competition in sites with large grazers. The activities of bison resulted in higher growth and reproduction for all six forb species studied and higher forb species richness. Habitats with bison were also characterized by much higher seed reproduction but no differences in vegetative reproduction compared to habitats without large grazers. Patterns of biomass allocation also showed high plasticity in these species, with reduced allocation to stem and increased allocation to reproduction in habitats with bison. The results of this study provide evidence the activities of bison reduce grass-forb competition, and that release from aboveground competition with grasses increases the growth, seed reproduction, abundance, and ultimately the diversity of perennial forb species in tallgrass prairie. The results further indicate perennial forbs in tallgrass prairie show high phenotypic plasticity in life history traits such as growth, reproduction, and resource allocation patterns.
This research addresses three primary goals: (1) to ascertain the genetic diversity of natural populations of Euhrychiopsis lecontei, a biological control agent currently used for the management of the invasive aquatic weed, Eurasian watermilfoil; (2) to determine the presence of any potential cryptic species of E. lecontei; and (3) to examine the phylogeography of E. lecontei to determine whether geographic patterns are identifiable in the genetic diversity. Sequence data from the cytochrome c oxidase subunit I (COI) gene were determined for E. lecontei from 35 populations throughout their native range in North America. A maximum likelihood tree indicates all haplotypes of E. lecontei form a monophyletic group. Based on branch lengths, the tree indicates there are two major subgroupings of haplotypes. This tree structure is further supported by the haplotype network, the SAMOVA results, and the geographic barrier to gene flow which clearly demonstrates genetic and geographic structuring within the species. Multiple lines of evidence support the hypothesis all individuals sampled from a broad geographic region throughout E. lecontei's range represent a single species. No cryptic species were discovered in this study, although distinct geographic and genetic structuring was revealed, likely due to current geographic isolation of the sampled waterbodies, as well as the locations of historical glacial refugia.
The spread of weedy plant species is a constant and increasing problem in the United States. A number of weed seed dispersal mechanisms are recognized, but one that may not have received attention is the potential for movement via the production and distribution of bagged soils for commercial sale. Our objective was to test the most common and inexpensive soils available at gardening supply stores in South Carolina for the presence of weeds. We identified 80 species or genera from 20 families in 19 different soil products. Most of the species were ubiquitous and many are restricted to the southern states, but some species are locally uncommon. We suggest the movement of different genotypes, even of common weeds, may create new evolutionary potential that could have long-term consequences for local adaptation of these species. The constant influx of weed seeds also creates propagule pressure and could contribute to further spread. We recommend commercial soil producers and distributors take steps to reduce the densities of viable weed seeds in their products.
An event of numerous adults of Platyneuromus honduranus (Navás) gathering near the Usumacinta River in Chiapas state, Mexico, is reported. A sex ratio of 1:1.4 (male to female) was observed on a sample taken (n = 44), and it is compared to recorded sex ratios for other megalopteran species in the Sialidae and Chauliodinae. Oviposition far from the water is documented and discussed.
Consumption of fine-textured soils by birds is common in South and Central America and some parts of Southeast Asia. Many bird species eat fine-textured soils to aid in digestion, detoxification, and mineral supplementation, but there are few documented cases of such behavior in North America. Here, I describe the consumption of clay soils from an expansive clay bank in north-central British Columbia, Canada by a Northern Flicker (Colaptes auratus L.) in the autumn of 2015. Texture analysis of soils used by the Flicker and collected from the clay bank indicated the soil texture was 61.84% silt, 38.16% clay, and 0.00% sand, which is similar to soils eaten by tropical birds where geophagy has been recorded. Trace element analysis indicated total concentrations of main elements tested ranged from 9 ppm for boron to nearly 40,000 ppm for iron, while minor elements ranged from below detectable limits for mercury, molybdenum, antimony, selenium, and tin to over 1700 ppm for titanium. Total concentrations (1510 ppm) and exchangeable cations (1.5 CMOL /Kg) of sodium in soils used by the Flicker were nearly identical to those found in soils used by tropical birds. Exchangeable cations were below detectable limits for iron and were 4.8 and 7.8 CMOL /Kg for calcium and magnesium, respectively. Total nitrogen, carbon, and sulfur were all below 0.38 weight percent. What drove this Flicker to geophagy is unknown, but the literature and the bird's pattern of use suggest the bird may have consumed these soils as a way to boost mineral intake or as a way to detoxify plant metabolites found in local fruits such as elderberries and wild cherries that Flickers are known to consume.