Birdwood's Mucuna - Dangling "Birds" on a Tree

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The "Rice Bird" that fed on crops in fields used to cause great headaches for farmers. Legend had it that Iron-Crutch Li of the Eight Immortals used magic to hang the naughty birds along a climber, and released them only during Ching Ming Festival. Birdwood's Mucuna is the climber that bears the legendary "birds".

Birdwood's Mucuna (Mucuna birdwoodiana) is a large native climber belonging to the family Fabaceae. It is commonly seen in local woods. The species blossoms in spring and early summer, corresponding to the time of Ching Ming when the "Rice Birds" (Yellow-breasted Emberiza aureola) Buntings were released in the legend. The long inflorescence is crowded with flowers. A single one can bear 20 to 30 flowers. The colours vary from pale green to pale yellow and sometimes white.

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The flower of Birdwood's Mucuna resembles a bird, rather than a butterfly as the Chinese family name indicates. The outermost petal (vexillum) seems like the head of the bird, the two petals on the side are the wings and the middle curled petals look like the tail! A pale yellow flower would most resemble the "Rice Bird". A cluster of flowers look so much like a flock of rice birds packed together! It is for this reason that people named the flowers "Rice Bird Flower" in Chinese.

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Pollination by bats

By contrast with the commonly seen Birdwood's Mucuna, there is a close relative of it - Hong Kong Mucuna (Mucuna championii) - that is very rare in Hong Kong. The species was first discovered in Hong Kong and can only be found in Hong Kong and Shenzhen. It is classified as "Endangered" in China. The flowers of the two species look similar, though those of the latter are purple and smaller. The fruits, however, are quite different: legumes of Hong Kong Mucuna look strange with many folds, while those of Birdwood's Mucuna are slender and resemble string of beads.

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Many plants rely on insects such as butterflies and bees for pollination. Birdwood's Mucuna, on the other hand, pollinates with the help of bats. Bats are more effective pollinators as they fly far and can carry large amounts of pollen. Bats identify distance and direction by sound waves, and some species of Mucuna have developed a special acoustic guide by turning the vexillum into a concave surface which reflects the ultrasound echo of bats and hence catches their attention.