Eric T. Linder

Breeding bird response to field border presence and width.

Abstract Avian communities can benefit from reconstructed herbaceous, strip habitats among agriculture; however, any benefits may be limited by width-dependent factors such as edge effects. We used 2 years of strip-transect surveys to evaluate avian density, richness, and conservation value between non-, narrow (mean width  =  8.2 m), and wide (mean width  =  40.7 m) field borders on intensive row-cropped field margins in the agriculture-dominated Mississippi Alluvial Valley. Wide field borders supported two times more birds (7.0 birds/0.2 ha) than narrow borders (3.6 birds/0.2 ha), which supported six times more birds than no border (0.6 birds/0.2 ha). Mean bird species richness was over five times greater in bordered (0.80–1.10 species/0.2 ha) than non-bordered margins (0.14 species/0.2 ha), but was largely uninfluenced by border width. We documented more bird use of agricultural fields and wooded fencerows adjacent to bordered than non-bordered margins. Red-winged Blackbirds (Agelaius phoeniceus) and Dickcissels (Spiza americana) had the strongest positive response to field border presence and width. Wide borders attracted high densities (2.0 birds/0.2 ha) of Dickcissels, an edge-sensitive species, suggesting the conservation potential of herbaceous vegetation patches <50 m of wooded edges for grassland birds. Extensive implementation of field borders, particularly of enhanced width, may contribute substantially to grassland bird conservation strategies in intensive, agricultural landscapes, although confirmation of these benefits requires additional demographic information.

Winter Avian Community and Sparrow Response to Field Border Width

Abstract Transformations of agricultural practices in the southeastern United States have drastically reduced preexisting quantities of strip-cover habitat along field margins. The National Conservation Buffer Initiative has promoted the establishment of herbaceous field borders to restore wildlife benefits once provided by such habitat. We evaluated effects of native warm-season grass field border establishment and width on winter bird response. Narrow (approx. 8-m) field borders represented a marginal improvement to non-bordered margins that were cropped ditch to ditch, whereas wide (approx. 30-m) borders significantly enhanced total avian conservation value, abundance, species richness, and sparrow abundance compared to non- or narrow borders. Furthermore, presence of wide borders altered bird use of row-crop fields. We observed increased sparrow (Emberizidae) abundances in agricultural fields adjacent to wide borders, which likely resulted from enhanced waste grain foraging opportunities. Given these benefits to wintering farmland birds, we advocate the integration of herbaceous field border habitat in agricultural landscapes, particularly borders of enhanced width.

Tardigrades of Alaska: distribution patterns, diversity and species richness

During the summer of 2010, a biotic survey of tardigrades was conducted along a latitudinal transect in central Alaska from the Kenai Peninsula, via Fairbanks and the Arctic Circle to the coastal plain. Work was centred at the Toolik and Bonanza Creek Long Term Ecological Research Network sites and supplemented by opportunistic collections from the Kenai Peninsula and Anchorage areas. The 235 samples collected at 20 sites over 10 degrees of latitude yielded 1463 tardigrades representing two classes, three orders, 10 families, 23 genera and 73 species from 142 positive samples. A total of 50 species are new to Alaska, increasing the states known species richness to 84. Several environmental metrics, such as pH, substrate, elevation, location and habitat were measured, recorded and analysed along the latitudinal gradient. Contrary to expectations, pH did not appear to be a predictor of tardigrade abundance or distribution. Density and species richness were relatively consistent across sites. However, the assemblages were highly variable within and between sites at only 14–20% similarity. We detected no correlation between species diversity and latitudinal or environmental gradients, though this may be affected by a high (59.9%) occurrence of single-species samples (containing individuals of only one species). Estimates of species richness were calculated for Alaska (118) and the Arctic (172). Our efforts increased the number of known species in Alaska to 84, and those results led us to question the validity of the estimate numbers.

Biotic and Abiotic Factors Governing Nestling-Period Length in the Ovenbird (Seiurus aurocapilla)

ABSTRACT. In many songbirds, the nesting period for a breeding attempt is extremely short, often lasting only a few weeks. Breeding adults can shorten this period by decreasing the number of eggs laid or reducing the length of the nestling period. Nestling-period length has received little attention in the literature but could have profound effects on annual fecundity, because each day represents a risk of nest depredation. Consequently, we were interested in assessing the biotic and abiotic factors that govern the nestling period in the Ovenbird (Seiurus aurocapilla). We provide evidence that food availability, more than predation pressure and climatic factors, influences nestling-period length, with increases in food availability decreasing the nestling period. We suggest that the nestling period is dictated by physiological constraints, which may be influenced by food availability and, thus, the ability to provision young. However, the greatest variation in nestling period was individual variation among breeding pairs. Thus, we believe that large-scale variation in ecological and environmental factors may determine the physiological constraints of the nestling period but parental behavior and quality within this framework dictate the actual length of the nestling period.

Are urban and rural tardigrade (Tardigrada) communities distinct and determined by pH: A case study from Fresno County, California

Abstract Tardigrades were collected from 73 urban sites and 24 rural locations in Fresno County, California to determine if differences existed in community structure between the two environments. Only 22 percent of urban samples were positive for tardigrades, as compared to 74 percent of rural samples. Samples from urban sites contained significantly fewer species than rural sites, although the average density did not vary significantly between urban and rural sites. Twenty-six different species were identified, with seven exclusively in the urban samples, 16 found only from rural samples, and three species found in both environments. Similarity analysis indicated urban communities were more similar to one another compared to similarities among rural communities, indicating significant differences between urban and rural communities. Tardigrades appeared to prefer habitat with a lower pH in both urban and rural locations. While our findings do support the negative relationship between urban sites and tardigrade richness, it was not explained by the lower pH typically associated with urban habitats. Further, we identified two species of Isohypsibius not previously recorded in the Western Hemisphere. The genus Eremobiotus was found for the first time in the Americas, and a species of Ramazzottius for the first time in North America.