Crossbills (Loxia spp.) provide a classical avian model of ecological specialization on food resources. Previous studies have suggested that morphometric, genetic and vocal diversification among Common Crossbill Loxia curvirostra populations is better explained by ecological distance (use of different conifers) than by geographical distance, indicating that populations have diverged adaptatively. We tested for adaptive divergence in Iberian crossbills using bill and body size measurements of 6082 crossbills from 27 sites, each consisting of a dominant or single pine (Pinus) of four possible species. Crossbills using different pines differed significantly in body size and bill size and shape. There was no correlation between geographical and morphological distance among sampling sites, consistent with the hypothesis that the morphological divergence of Iberian crossbills is shaped by their ecological differences (foraging on alternative conifers) rather than geographical distance. However, for unknown reasons, Common Crossbills foraging on Pinus sylvestris in Iberia have on average much smaller bills than Parrot Crossbills Loxia pytyopsittacus feeding on the same pine species in northern Europe. The extent to which crossbills specialize on Iberian P. sylvestris remains to be established. Specialization on conifers with overlapping geographical distributions may be facilitated by matching habitat choice of crossbills as a function of their local intake rates.

中文翻译：

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西班牙常见的小嘴鸟种群之间的形态差异和对不同松树物种的适应

b（Loxia spp。）提供了一种经典的禽类生态模型，即食物资源的生态专业化。先前的研究表明，普通Cross嘴猴Loxia curvirostra种群之间的形态，遗传和声音多样性通过生态距离（使用不同的针叶树）比通过地理距离更好地解释，这表明种群已经适应性地分化了。我们测试了在伊比利亚自适应发散使用的6082个crossbills账单和身体尺寸测量crossbills从27位点，每个都包括显性或单松树（松）的四个可能的物种。使用不同松树的交叉票据在车身尺寸，票据尺寸和形状上有显着差异。采样地点之间的地理距离与形态距离之间没有相关性，这与伊比利亚斜嘴鸟的形态差异是由它们的生态差异（在替代针叶树上觅食）而不是地理距离所决定的假设相一致的。但是，出于未知原因，在伊比利亚的以樟子松为食的普通犀鸟的平均账单要比以北欧相同松树为食的鹦鹉犀鸟Loxia pytyopsittacus的账单小得多。的程度上crossbills伊比利亚专门化P.樟子松有待确定。通过根据其当地摄入量来匹配交叉点的栖息地选择，可以促进地理分布重叠的针叶树的专业化。