Avian Foraging Patterns in Crop Field Edges Adjacent to Woody Habitat

As natural predators of pest insects, woodland birds provide biological pest suppression in crop fields adjacent to woody edges. Although many birds using these habitats forage widely, earlier studies have found that most foraging activity occurs within 50 m of the woody edge. The goals of this study were to determine the primary area of use, or functional edge, for birds foraging in crop fields adjacent to woody edges, and to evaluate their foraging distance patterns. During the summers of 2005 and 2006, avian foraging behavior was observed at 12 research sites in east central Nebraska that contained either a shelterbelt or woody riparian edge. At each site, perches were provided at 10 m intervals out from the edge and insect larvae were placed in feeders at random locations to simulate a pest insect food resource. Birds were recorded foraging in five distance categories out from the edge (0–10, 10–20, 20–30, 30–40, and 40–50 m). Seven species foraged primarily within 20 m of the edge (72% all observations; 79% without perch or feeder observations). Ten species foraged throughout the plots but six of these generally foraged more often (45% and 49%) and four less often (30% and 30%) within 20 m of the edge. The 13 species that tended to forage more often within 20 m of the edge, with 56% of their foraging overall in this area, also tended to forage farther when perch and feeder observations were included, indicating willingness to forage farther when food resources were available. Based on a repeated measures analysis of variance, foraging distances appeared to be greater at sites with soybean as the planted crop, although this apparent trend was significant for only some species. There was no clear difference in foraging distances outward from shelterbelt versus riparian sites. These results indicate that conservation efforts within the 20 m functional edge offer potential to enhance the sustainability of both birds and crops in agricultural

Avian Foraging Patterns in Crop Field Edges Adjacent to Woody Habitat

As natural predators of pest insects, woodland birds provide biological pest suppression in crop fields adjacent to woody edges. Although many birds using these habitats forage widely, earlier studies have found that most foraging activity occurs within 50 m of the woody edge. The goals of this study were to determine the primary area of use, or functional edge, for birds foraging in crop fields adjacent to woody edges, and to evaluate their foraging distance patterns. During the summers of 2005 and 2006, avian foraging behavior was observed at 12 research sites in east central Nebraska that contained either a shelterbelt or woody riparian edge. At each site, perches were provided at 10 m intervals out from the edge and insect larvae were placed in feeders at random locations to simulate a pest insect food resource. Birds were recorded foraging in five distance categories out from the edge (0–10, 10–20, 20–30, 30–40, and 40–50 m). Seven species foraged primarily within 20 m of the edge (72% all observations; 79% without perch or feeder observations). Ten species foraged throughout the plots but six of these generally foraged more often (45% and 49%) and four less often (30% and 30%) within 20 m of the edge. The 13 species that tended to forage more often within 20 m of the edge, with 56% of their foraging overall in this area, also tended to forage farther when perch and feeder observations were included, indicating willingness to forage farther when food resources were available. Based on a repeated measures analysis of variance, foraging distances appeared to be greater at sites with soybean as the planted crop, although this apparent trend was significant for only some species. There was no clear difference in foraging distances outward from shelterbelt versus riparian sites. These results indicate that conservation efforts within the 20 m functional edge offer potential to enhance the sustainability of both birds and crops in agricultural

Effects of Stock Use and Backpackers on Water Quality in Wilderness in Sequoia and Kings Canyon National Parks, USA

During 2010-2011, a study was conducted in Sequoia and Kings Canyon National Parks (SEKI) to evaluate the influence of pack animals (stock) and backpackers on water quality in wilderness lakes and streams. The study had three main components: (1) a synoptic survey of water quality in wilderness areas of the parks, (2) paired water quality sampling above and below several areas with differing types and amounts of visitor use, and (3) intensive monitoring at six sites to document temporal variations in water quality. Data from the synoptic water quality survey indicated that wilderness lakes and streams are dilute and have low nutrient and Escherichia coli concentrations. The synoptic survey sites were categorized as minimal use, backpacker-use, or mixed use (stock and backpackers), depending on the most prevalent type of use upstream from the sampling locations. Sites with mixed use tended to have higher concentrations of most constituents (including E. coli) than those categorized as minimal-use (P ≤ 0.05); concentrations at backpacker-use sites were intermediate. Data from paired-site sampling indicated that E. coli, total coliform, and particulate phosphorus concentrations were greater in streams downstream from mixed-use areas than upstream from those areas (P ≤ 0.05). Paired-site data also indicated few statistically significant differences in nutrient, E. coli, or total coliform concentrations in streams upstream and downstream from backpacker-use areas. The intensive-monitoring data indicated that nutrient and E. coli concentrations normally were low, except during storms, when notable increases in concentrations of E. coli, nutrients, dissolved organic carbon, and turbidity occurred. In summary, results from this study indicate that water quality in SEKI wilderness generally is good, except during storms; and visitor use appears to have a small, but statistically significant influence on stream water quality