Assessment of Chatham Island as a location for liberation of black stilts
Assessment of Chatham Island as a location for liberation of black stilts
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对查塔姆岛作为黑高跷解放地点的评估
DOI：
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发表时间：
2007
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通讯作者：
D. P. Murray
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文献类型：
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作者：
D. P. Murray
在我们遇到的高水位下，Te Whanga泻湖及其附近地区很大程度上不适合使用黑色高跷。然而，在这个水位上存在的浅水觅食栖息地的面积将足以维持它们的数量。在低水位时，大片浅滩可供黑色高跷使用。合适的筑巢地点通常很小，分散在远离主泻湖的地方。环礁湖的边缘不适合筑巢，因为它容易受到风力产生的水位波动的洪水影响。与麦肯齐盆地浅水区的生物量相比，高水位浅水区水生无脊椎动物的生物量相对较低，但足以生产黑色高跷。现有的猎物种类很容易被它们捕获和吃掉。低水位时食物供应的类型和数量尚不清楚。查塔姆岛的内陆水域一般为棕色、咸水、碱性和高溶解氧。它们在冬天比麦肯齐盆地的水域更温暖。更温暖的条件可能会导致查塔姆岛浅水地区冬季粮食产量高于上威塔基盆地浅水地区。在查塔姆岛上可以看到27只高跷。这很可能是整个人口，或者接近这个数字。尽管高脚高跷可能会定期往返新西兰大陆，但两只幼崽的出现表明它们也在岛上繁殖。种群规模小，成体与幼体的比例高，表明繁殖成功率较低。高脚高脚的取食率和搜索率与冬季黑高跷的取食率和搜索率相似。这种相似性进一步支持了查塔姆岛上的食物供应足以制造黑高跷的结论。威卡似乎在任何地方都有大量的存在。猫科动物、大鼠和负鼠都存在，但它们的密度和分布尚不清楚。Kahu(近似马戏团)存在，但密度比Macken-zie盆地低得多。这些捕食者，特别是韦卡，对黑色高跷的潜在影响可能与麦肯齐盆地捕食者目前的影响一样严重。通过创建更好的筑巢区域和竖起屏障，将捕食者排除在东部吐痰区域或个别池塘周围，有很好的潜力来改善黑高跷的栖息地。
At the high water level that we encountered, Te Whanga Lagoon and its immediate environs are largely unsuited to black stilts. Nevertheless, the area of shallow-water foraging habitat that does exist at this water level would be sufficient to maintain a population of them. At low water levels, large areas of shallows would be available to black stilts. Suitable nesting sites are generally small and scattered away from the main lagoon. The lagoon edge would be unsuitable for nesting because it is susceptible to flooding by wind-generated water level fluctuations. Biomass of aquatic invertebrates in the shallows at high water level are relatively low compared to biomass in shallows in the Mackenzie Basin but would be adequate for black stilts. The types of prey species present would be easily caught and eaten by them. The type and quantity of food supplies at low water levels is unknown. The inland waters on Chatham Island are generally brown, saline, alkaline, and high in dissolved oxygen. They are warmer in winter than waters of the Mackenzie Basin. The warmer conditions are likely to result in higher winter food production in Chatham Island shallow waters than in shallow waters of the Upper Waitaki Basin. Twenty seven pied stilts were seen on Chatham Island. This was probably the entire population, or close to it. Although pied stilts may regularly move to and from mainland New Zealand, the presence of two juveniles indicates that they also breed on the island. The small population size, and high adult to juvenile ratio suggest that breeding success is low. Pied stilt feeding and searching rates were similar to feeding and searching rates of black stilts in winter. This similarity provides further support for the conclusion that food supplies on Chatham Island would be adequate for black stilts. Wekas appear to be present in high numbers everywhere. Cats, rats and pos-sums are present but their density and distribution are unknown. Kahu (Circus approximans) are present but at much lower density than in the Macken-zie Basin. The potential effects on black stilts of these predators, particularly wekas, may be just as serious as the present effects of predators in the Mac-kenzie Basin. There is good potential to enhance the habitat for black stilts by creating better nesting areas and by erecting barriers to exclude predators from the eastern spit area, or around individual ponds.