Size and Structure of a Wintering Avian Community in Southern Texas
Size and Structure of a Wintering Avian Community in Southern Texas
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德克萨斯州南部越冬鸟类群落的规模和结构
DOI：
10.2307/1934089
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发表时间：
1972
期刊：
影响因子：
--
通讯作者：
J. Emlen
中科院分区：
文献类型：
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作者：
J. Emlen
越冬的陆地鸟类的25.4平方公里的面积集中在焊工野生动物保护区是南部得克萨斯州进行系统的计数，计数被转换为绝对密度值，通过应用经验得出的转换因子校正变量的可检测性和减少调整后的值到一个共同的面积基地。植被被绘制成地图，7种植被类型-两个草地，三个灌木丛，两个林地和河流森林-被确认和定义的测量沿着突出参数的植被地貌。组成陆地鸟类群落的50种鸟类的总密度为918只，每平方公里的鸟类生物量为96公斤（371只，85磅）。每100英亩）。不包括体重较大的野生火鸡和Bobwhite鹌鹑，有729只，每平方公里33公斤。冬季入侵者的数量超过永久居民的物种，但有较少的个人和较小的生物量。没有鹌鹑和火鸡，有更多的个人食草动物比食虫动物，但较小的食草动物生物量，无论是在冬季入侵者和永久居民类别。冬季入侵的食草动物主要是小种子觅食者。物种数和物种多样性（H '）在乔木和高灌木生境中高于开阔草原，灌丛介于两者之间。密度和生物量高，在树林和开放的栖息地和低的灌木丛。反映在每个栖息地的物种多度曲线的陡峭程度的公平性的措施表现出较低的价值（陡峭的曲线）在森林和灌木草原栖息地。冬季入侵者在林地中的表现相对最好，在灌木丛中的表现最差。然而，在绝对数量上，它们在森林中最高。食虫动物在灌木丛中比在森林栖息地的草原中更有代表性。每种鸟类在七个栖息地都表现出独特的分布模式;有些是高度的真栖性，出现在所有栖息地;其他的则仅限于一个或多个栖息地。的Bobwhite鹌鹑占主导地位（密度最高），在所有植被类型，除了森林是红衣主教是一个强大的优势。前四名的物种在每个类型包括从55%到80%的类型的组合人口。生态振幅指数给出的数值从林地的野火鸡的0.00到无处不在的知更鸟的0.96不等。生态幅度与迁徙状态或食物习惯没有相关性。生态重叠的指数，得出每个两个物种的组合，通过总结的差异，代表性的两个在七个栖息地，并除以这个总数的最大可能的分数，如果这两个物种有相同的生态分布。数值范围从1%（白喉麻雀x萨凡纳麻雀）到94%（隐士画眉x红冠小王）。类别间二分体（夏季-冬季）的重叠量介于两个类别内二分体（夏季-夏季和冬季-冬季）的重叠量之间。一个二维排序描绘的内在生态独特性的共同物种在社会上显示了三个集群的点和一个单一的隔离。这三个集群对应于草原，森林，森林，灌木丛组，隔离是一个stenotopic灌木丛物种。永久居民和冬季入侵者在每组中都有很好的代表性。
The wintering land birds of a 25.4—km2 area centered at the Welder Wildlife Refuge is southern Texas ware subjected to systematic counting, and the counts were converted to absolute density values by applying an empirically derived conversion factor correcting for variable detectability and reducing the adjusted values to a common areal base. The vegetation was mapped, and seven vegetation types–two of grassland, three of brushland, and two of woodland and riverine forest–were recognized and defined in terms of measurements along prominent parameters of the vegetational physiognomy. The combined density for the 50 species constituting the land bird community was 918 individuals and 96 kg of avian biomass per km2 (371 individuals and 85 lb. per 100 acres). Discounting the heavy—bodied Wild Turkeys and Bobwhite Quail, there were 729 individuals and 33 kg per km2. Winter invaders outnumbered permanent residents in terms of species but had fewer individuals and a smaller biomass. Without the quail and turkey, there were more individual granivores than insectivores, but a smaller granivore biomass, both in the winter invader and the permanent resident categories. Winter invader granivores were primarily small—seed foragers. The number of species and the species diversity (H') were higher in the habitats containing trees and high shrubs than in open prairies; brushlands held an intermediate position. Densities and biomass were high in the wooded and open habitats and low in the brushlands. A measure of equitability reflecting the steepness of the species abundance curve in each habitat showed low values (steep curves) in the forest and scrubby prairie habitats. Winter invaders were relatively best represented in the woodlands and most poorly represented in the brushlands. In absolute numbers, however, they were highest in the forest. Insectivores were better represented in the brushlands than in either the prairies of wooded habitats. Each bird species showed a distinctive pattern of distribution through the seven habitats; some were highly eutytopic, appearing in all habitats; others were restricted to one or to. The Bobwhite Quail dominated (highest density) in all vegetation types except the forest were the Cardinal was a strong dominant. The top four species in each type comprised from 55% to 80% of the combined population of the type. An index of ecological amplitude gave values ranging from .00 in the Wild Turkey of the woodlands to .96 in the ubiquitous Robin. No correlations of ecological amplitude with migratory status or food habits were detected. An index of ecological overlap was derived for each two—species combination by summing the differences in representation of the two in the seven habitats and dividing this total by the maximum possible score achieved if the two species had identical ecological distributions. Values ranged from 1% (White—throated Sparrow x Savannah Sparrow) to 94% (Hermit Thrush x Ruby—crowned Kinglet). The amount of overlaps in the between—category dyads (summer—winter) was intermediate between the overlaps in the two intracategory dyads (summer—summer and winter—winter). A two—dimensional ordination depicting the intrinsic ecological distinctness of the commoner species in the community shows three clusters of points and a single isolate. The three clusters correspond to grassland, forest, and forest—brushland groups; the isolate is a stenotopic brushland species. Both permanent residents and winter invaders were well represented in each group.