Feeding strategies: 2. Birds feeding on palm fruits

posted in: Feeding strategy, Feeding-plants | 0

The talipot palm (Corypha umbraculfiera) (above) is one of the largest palm in the world. It flowers only once, after 50-70 years, giving forth a massive inflorescence 3-7 metres high and 10-13 metres across. More than 20 million tiny flowers are borne on this, the largest inflorescence in the plant kingdom. The flowers take about 13 months to develop, and during this time all the food reserves accumulated in the stem during the lifetime of the palm are transferred to the developing fruits. Once the fruits are matured and lie scattered below, the palm slowly dies. The above image was taken at the Singapore Botanical Gardens in December 2004. However, I am not aware of any birdwatchers making observations on birds eating these fruits. Hopefully, with the current flowering of the palm/s in the gardens, someone would document this unknown aspect of the talipot palm biology.

Check out this LINK for more information on the flowering talipot palm at the Singapore Botanical Gardens.

Palms are a group of erect trees, shrubs and climbers (eg. rattans). The palm has a single stem, growing singly or in a clump, sometimes branched. Leaves are compound or simple, large and borne mostly at the top of the stem. Flowers are small, unisexual or bisexual. Fruits are single seeded, usually with an outer softer covering. The seed is tough, consisting of the stone-like endosperm, which is actually a storage product, sometimes referred to as albumin (left: TS of seed).

Palm fruits are a source of food for birds LINK. The birds feed on the pulpy outer layer by either pecking on it or swallowing the entire fruit whole. If swallowed, the seed would either be regurgitated after a short while or passed through the gut and expelled at the other end. Whether the bird pecks or swallows would depend on the gape of the bird and the size of the fruit.

The Asian Koel (Eudynamys scolopacea) and Asian Glossy Starling (Aplonis panayensis) swallow the large fruits of Alexandra palm (Archontophoenix alexandrae), to regurgitate the cleaned seed within a short period of time LINK 1, LINK 2. Yellow-vented Bulbul (Pycnonotus goiavier) on the other hand does not swallow but takes small pieces LINK. Similarly, the Orange-bellied Flowerpecker (Dicaeum trigonostigma) pecks on fruits of Golden Cane Palm (Dypsis lutescens) LINK.

Not passing the seeds through their gut and regurgitating them later allows the bird to feed on more fruits at any one time. Taking the seeds into the gut fills up the space as well as adds weight to the bird that may impede proper flight.

Pied Imperial Pigeons (Ducula bicolor) swallow the fruits of fan palms (Livistona sp.) whole. LINK. Whether they regurgitate the seed has yet to be confirmed. Ecologist Prof Richard Corlette, in a comment to the post, has this to say: “I have just seen the same Bird-Park flock feeding on the same species of Livistona at NUS. They swallow the fruits whole and there is no sign of regurgitated seeds anywhere nearby. My guess is that the seeds pass right through the guts and are defecated. The fruits are c. 22 mm diameter and I have seen no other birds take them – not even the koels. Imperial pigeons may be the world’s best seed dispersal agents!” It should be noted that birds that regurgitate the seeds they swallow do not help in their dispersal as the seeds are dropped below the plant and not some distance away.

The Pink-necked Green Pigeon (Treron vernans) has been seen swallowing the fruit of the MacArthur palm (Ptychosperma macarthurii) whole LINK but there has been no documentation of it regurgitating the seed. Wonder whether the pigeon’s powerful gizzard can grind the fruit together with the seed?

Hornbills have been known to swallow Oncosperma fruits whole but not been observed regurgitating the seeds. Presumable, being such large birds, carrying the seeds in their gut may not have any effect on their ability to feed on more fruits or even their flying. LINK.

Parrots and parakeets grasp on to the oil palm fruits (Elaeis guineensis) with one foot and using their powerful bill, tear off the oil-rich fibrous outer layer to eat. They are thus not seed dispersers of the oil palm LINK.

YC Wee
February 2013

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