On the verge of extinction:: a survey of the mangrove finch Cactospiza heliobates and its habitat on the Galapagos Islands
On the verge of extinction:: a survey of the mangrove finch Cactospiza heliobates and its habitat on the Galapagos Islands
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DOI：
10.1017/s0030605304000316
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发表时间：
2004-04-01
期刊：
影响因子：
2.7
通讯作者：
Tebbich, S
中科院分区：
文献类型：
--
作者：
Dvorak, M;Vargas, H;Tebbich, S
极度濒危的红树林雀Cactospiza（=Camarhynchus）heliobates现在仅限于加拉帕戈斯群岛的伊萨贝拉岛，只在红树林中发现。以前它也出现在邻近的费尔南迪纳岛，但显然在那里灭绝了。直到1994年，该物种的种群规模和生态学才相对未知。我们在1996年至2000年期间对该物种进行了调查、生境评估和行为观察。虽然伊萨贝拉岛有大约760公顷的红树林，但只有在西北海岸的两个地点证实了繁殖，总面积为32公顷。我们估计这两个地区的人口为100人。此外，在东南海岸发现了3-5个领地（可能包含繁殖个体）。栖息地参数的比较表明，树高和枯木量显着高于领土内比外，因此，这些可能是重要的栖息地组成部分，该物种。由于在伊萨贝拉的两个主要种群和所有其他红树林之间发现了相当大的结构差异，后者似乎可能是次优生境。因此，我们得出结论，该物种分布非常有限的原因之一是迄今未知因素造成的栖息地退化。
The Critically Endangered mangrove finch Cactospiza (=Camarhynchus) heliobates is now confined to Isabela Island in the Galapagos Islands and is exclusively found in mangrove forests. Formerly it occurred also on neighbouring Fernandina Island, but is apparently extinct there. The population size and ecology of the species was relatively unknown until 1994. We conducted surveys, habitat assessments and behavioural observations of the species between 1996 and 2000. Although Isabela Island has approximately 760 ha of mangrove forests, breeding was confirmed at only two sites, comprising 32 ha in total, on the north-western coast. Our estimate of the population in these two areas is 100 individuals. Additionally, 3-5 territories (which probably contained breeding individuals) were discovered on the south-eastern coast. A comparison of habitat parameters showed that tree height and amount of dead wood were significantly higher within than outside territories, and these are therefore likely to be important habitat components for this species. As considerable structural differences were detected between the two sites holding the main populations and all other mangrove stands on Isabela, it seems possible that the latter are sub-optimal habitat. We therefore conclude that one of the reasons for the very limited distribution of the species is habitat degradation caused by hitherto unknown factors.