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首页> 外文期刊>Journal of Avian Biology >Temporal variation in breeding and cone size selection by three species of crossbills Loxia spp. in a native Scots pinewood
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Temporal variation in breeding and cone size selection by three species of crossbills Loxia spp. in a native Scots pinewood

机译：三种斜喙猴Loxia spp在繁殖和视锥大小选择上的时间变化。在苏格兰本地的松林中

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The breeding biology and cone size selection of crossbills was studied mainly during 1995 to 2002 at Abernethy Forest, Scotland, an ancient native Scots pine Pinus sylvestris wood, where only a single crossbill species, the Scottish crossbill Loxia scotica, was assumed to occur and to be adapted to feed on seeds in Scots pine cones. However, three crossbill species (common Loxia curvirostra, Scottish and parrot crossbills Loxia pytyopsittacus) nested in some years, with the parrot crossbill being the most abundant. Most nests were in old large pines, with the three crossbill species not differing in their use of tree size or stand density for nesting. The mean clutch and brood sizes were 3.8 and 2.9, and their mean survivals were 86 and 74%, respectively, with no significant differences among species. The timing of breeding differed between species, with parrot crossbills breeding earliest (median date 21 March, including second attempts) and common crossbills breeding last (median date 21 April), probably in response to the differing accessibility of Scots pine seeds to these species. The difference in the time of breeding may reduce mixed mating. Crossbills foraged preferentially on trees with small cones when the cones were closed. Small cones had thinner scales than large cones, suggesting that the preference for small cones was related to higher feeding rates on these cones when cones are closed. Such a preference was also found for captive crossbills with the Scottish crossbill showing a more pronounced preference for smaller cones than the larger-billed parrot crossbill. However, crossbills selected larger cones within trees and trees with larger cones once the cones opened in April. Such a shift occurred presumably because variation in scale thickness has little impact on seed accessibility once cones open, and larger cones have larger and more seeds. The greater ability of parrot crossbills to exploit seeds in closed Scots pine cones allowed parrot crossbills to start breeding earlier and to have young when seeds were most accessible. Only after the cones opened were the smaller-billed common crossbills able to easily access seeds and to start breeding. The time of breeding of Scottish crossbills was intermediate between common and parrot crossbills, and they probably had an intermediate ability to exploit Scots pine cones. The reason why there were few Scottish crossbills nesting in Abernethy Forest remains a puzzle, considering that native pine wood is assumed to be the ancestral habitat to which the Scottish crossbill is adapted. The breeding season for all crossbills ended in June, when most of the seed from a given cone cohort was shed. This is when starved broods were found, not associated with bad weather.
机译：主要在1995年至2002年期间，在苏格兰的Abernethy Forest（一种古老的苏格兰松木樟子松木）中研究了b鸟的繁殖生物学和视锥大小，在这种情况下，仅假设存在一种cross鸟物种，即苏格兰cross鸟Loxia scotica。适合以苏格兰松果的种子为食。但是，在几年中筑巢了三种cross鸟物种（常见的Loxia curvirostra，苏格兰和鹦鹉cross鸟Loxia pytyopsittacus），其中鹦鹉cross鸟数量最多。多数巢位于旧的大松树中，这三种斜纹小鸟在筑巢时使用的树木大小或林分密度没有差异。离合器和亲鱼的平均大小分别为3.8和2.9，平均成活率分别为86％和74％，物种间无显着差异。物种之间的繁殖时间有所不同，鹦鹉犀鸟最早繁殖（中位日期为3月21日，包括第二次尝试），而普通犀鸟繁殖最后一次（中位日期为4月21日），可能是由于苏格兰松树种子对这些物种的可及性不同。繁殖时间的差异可能会减少混合交配。当圆锥体关闭时，斜喙优先在具有小圆锥体的树上觅食。小圆锥体比大圆锥体的鳞片更薄，这表明小圆锥体的偏好与闭合圆锥体时这些圆锥体的进给速度更高有关。还发现了这样的偏爱，苏格兰的比尔比对圈养的犀鸟比较小的圆锥形比索更显着。但是，一旦四月锥状花序开放，交叉收费表就在树木中选择较大的锥状花序。据推测，发生这种变化是因为鳞片厚度的变化对锥孔打开后的种子可及性几乎没有影响，而较大的锥孔具有越来越大的种子。鹦鹉犀鸟在封闭的苏格兰松果中利用种子的能力更强，因此鹦鹉犀鸟可以更早地开始繁殖，并且在种子最容易获得时就可以幼小。只有在圆锥体打开后，较小嘴的普通斜嘴鸟才能轻松获得种子并开始育种。苏格兰cross的繁殖时间介于普通cross和鹦鹉intermediate之间，它们可能具有利用苏格兰松果的中等能力。考虑到当地的松木被认为是苏格兰cross适应的祖先栖息地，在Abernethy Forest内很少有苏格兰cross分布的原因仍然令人困惑。所有杂种的育种季节在六月结束，当时来自给定锥群的大多数种子都脱落了。这是在发现饥饿的雏鸟时，与恶劣的天气无关。

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