Habitat edge, land management, and rates of brood parasitism in tallgrass prairie.

Bird populations in North America's grasslands have declined sharply in recent decades. These declines are traceable, in large part, to habitat loss, but management of tallgrass prairie also has an impact. An indirect source of decline potentially associated with management is brood parasitism by the Brown-headed Cowbird (Molothrus ater), which has had substantial negative impacts on many passerine hosts. Using a novel application of regression trees, we analyzed an extensive five-year set of nest data to test how management of tallgrass prairie affected rates of brood parasitism. We examined seven landscape features that may have been associated with parasitism: presence of edge, burning, or grazing, and distance of the nest from woody vegetation, water, roads, or fences. All five grassland passerines that we included in the analyses exhibited evidence of an edge effect: the Grasshopper Sparrow (Ammodramus savannarum), Henslow's Sparrow (A. henslowii), Dickcissel (Spiza americana), Red-winged Blackbird (Agelaius phoeniceus), and Eastern Meadowlark (Sturnella magna). The edge was represented by narrow strips of woody vegetation occurring along roadsides cut through tallgrass prairie. The sparrows avoided nesting along these woody edges, whereas the other three species experienced significantly higher (1.9-5.3x) rates of parasitism along edges than in prairie. The edge effect could be related directly to increase in parasitism rate with decreased distance from woody vegetation. After accounting for edge effect in these three species, we found evidence for significantly higher (2.5-10.5x) rates of parasitism in grazed plots, particularly those burned in spring to increase forage, than in undisturbed prairie. Regression tree analysis proved to be an important tool for hierarchically parsing various landscape features that affect parasitism rates. We conclude that, on the Great Plains, rates of brood parasitism are strongly associated with relatively recent road cuts, in that edge effects manifest themselves through the presence of trees, a novel habitat component in much of the tallgrass prairie. Grazing is also a key associate of increased parasitism. Areas managed with prescribed fire, used frequently to increase forage for grazing cattle, may experience higher rates of brood parasitism. Regardless, removing trees and shrubs along roadsides and refraining from planting them along new roads may benefit grassland birds.     

Scale-dependent habitat selection in migratory frugivorous passerines

Frugivorous migrants may select fruit-rich habitats en route to attain high food rewards, yet their stopover behavior may also be shaped by other considerations, such as predation risk. During 1996–2001 we investigated autumn stopover habitat use of three Sylvia warblers (sylviids; S. hortensis, S. atricapilla and S. curruca) and three Turdidae chats (turdids; Cercotrichas galactotes, Oenanthe hispanica and Phoenicurus phoenicurus) in planted groves of the fruiting tree Pistacia atlantica in Lahav Forest, Israel, which is located at the edge of a desert. We used fecal analysis, a constant-effort trapping scheme and field observations to estimate the extent of frugivory, and bird habitat and microhabitat selection with regard to natural fruit and foliage densities. We also measured bird microhabitat selection in a set of fruit-manipulated trees. We trapped a total of 2,357 birds during the course of the study. Although sylviids exhibited higher frugivory level than turdids, both species groups exhibited a similar significantly positive correlation between bird and fruit densities at the habitat scale. However, at the microhabitat scale, sylviids selected densely foliated trees, whilst turdids were randomly distributed among trees. Our findings suggest that both species groups selected fruit-rich stopover habitats to take advantage of the high food availability before the demanding migration journey. No other mechanism except predation avoidance can explain the sylviids microhabitat selection; the migrants used foliage cover to reduce bird detectability by raptors. We conclude that en route passerines may use staging habitats in a sophisticated manner, by adopting scale-related behavior with regard to the availability of food and refuge cover.     

The role of distance,familiarity, and time of day in Carolina wrens responses to conspecific songs

Summary We tested two predictions of the ranging hypothesis (Morton 1982) which suggests that: (1) For distance estimation of singing intruders from them, birds compare degraded songs they hear to undegraded songs in their memory. (2) The strength of response of birds to songs depends on how well they can range the songs as coming from inside or outside the territory.In accordance with first prediction we found that, Carolina wrens discriminate significantly between songs played from outside to those played inside their territories only if they are familliar with the song type played (Fig. 1). In accordance with the second prediction, on the average, the birds in our study responded stronger to unfamiliar than to familiar songs when these were played from outside the territory, but stronger to familiar than to unfamiliar songs when played inside it (Fig. 2). We concluded that this was because they could range the familiar songs with greater certainty.The variance in the data was, in part, due to changes in the birds' responses during the day. We report for the first time, an increase in the strength of territorial defense of birds later in the morning, accompanied by a decrease in singing in response to song playback. We suggest that these changes reflect an increase in energy gain and worse acoustic conditions later in the day.     

如何在教学中做到“到位而不越位”——针对中年段语文教学的研讨

<正>中年级的语文阅读教学,既要完成本学段的学习目标,又要为高年级的阅读教学作准备,起着承上启下的作用,是学生语文学习的一个重要阶段。但是纵观中年段的语文课文安排,我们不难发现:有一些是原老教材的高年级课文,移到了中年级,如《太阳》《小英雄雨来》《西门豹》《一个中国孩子的呼声》等。这些文章篇幅长、内容深,对于中年级孩     

Shortened fetal long bones: a possible in utero manifestation of placental function

Shortened fetal long bones (SFLB) are usually indicative of a skeletal dysplasia. Our aim in this observational retrospective study was to describe a new association between SFLB, small for gestational age (SGA) fetuses and placental abnormalities, and to suggest an aetiologic explanation. During the last decade we have evaluated nine cases in which SFLB (more than 2SD below the mean) was associated with SGA, abnormal maternal serum placental hormones and abnormal placental sonography. Six cases had significantly increased second trimester maternal serum βhCG and four developed toxaemia of pregnancy or had chronic hypertension. On histology, mature placentas with vascular abnormalities, including chorangiosis, large infarcts and slightly increased syncytial knots were noted. The combination of SFLB, SGA fetuses and placental abnormalities (sonographic, as well as histological) suggested a possible common pathway in the aetiology of this association. Copyright © 2002 John Wiley & Sons, Ltd.     

Design considerations to enhance the safety of patient compartments in ambulance transporters

The safety of the interior of ambulances is dubious and, in the event of sudden impact during emergency transport, potentially perilous to patients they carry. The workplace ergonomics of the interior of the passenger cabin is lacking. This article discusses an improved ergonomic interior design based on study findings, observations and subjective perception. It suggests design aspects and safety concepts aimed at increasing the safety of patients and paramedic staff inside the ambulance as a mobile workstation.