Bird pollination is well-established in New World Bignoniaceae, but studies of species with floral traits suggestive of bird pollination in the Old World are lacking. Here we studied the pollination ecology of to test the prediction of pollination by specialist flower-visiting birds. Observations from multiple sites showed that both the Streaked Spiderhunter () and pollen-collecting bees were floral visitors. However, almost no fruit was produced if birds were excluded, suggesting that bees do not play a role in pollination, and that pollination is performed almost exclusively by birds in this self-incompatible tree. Measurements of floral traits revealed a typical bird pollination syndrome, and the nectar concentration and volume were both within the proposed ranges based on other flowers pollinated by specialist birds. However, the rather low level of sucrose (less than 2 %) in nectar sugar contradicts the expectation for nectar of flowers pollinated by specialist nectar-feeding birds. Although the Streaked Spiderhunter is among the longest-billed flower-visiting birds in Asia, its bill is only 2/3 of the corolla tube in length, suggesting that the bird can extend the tongue to access nectar. This study is the first to experimentally confirm bird pollination in the Old World Bignoniaceae. It also indicates aspects that are possibly characteristic of spiderhunter pollination systems, i.e. high degrees of specialization, unusual nectar sugar composition, and floral tubes much longer than bird bills.

中文翻译：

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亚洲双子树授粉的自然历史：长管花和不太长的鸟喙

鸟类授粉在新世界紫葳科植物中已得到充分证实，但对具有暗示旧世界鸟类授粉的花卉特征的物种的研究却很缺乏。在这里，我们研究了授粉生态学，以测试专业赏花鸟类对授粉的预测。多个地点的观察表明，条纹蜘蛛猎手（）和花粉采集蜂都是花卉访客。然而，如果排除鸟类，则几乎不会结出果实，这表明蜜蜂在授粉中不起作用，并且在这种自交不亲和的树中，授粉几乎完全由鸟类进行。花性状的测量揭示了典型的鸟类授粉综合症，花蜜浓度和体积均在基于专业鸟类授粉的其他花朵的建议范围内。然而，花蜜中蔗糖含量相当低（低于 2%），与专门以花蜜为食的鸟类授粉的花蜜的预期相矛盾。尽管条纹捕蛛鸟是亚洲最长嘴的赏花鸟类之一，但它的喙长度仅为花冠管的 2/3，这表明这种鸟可以伸出舌头来获取花蜜。这项研究是第一个通过实验证实旧大陆紫葳科鸟类授粉的研究。它还表明了蜘蛛猎手授粉系统可能具有的特征，即高度专业化、不寻常的花蜜糖成分以及比鸟嘴长得多的花管。