ABOVE: Out of the 21 species of pigeons found in Borneo,  5 species of Treron Green Pigeons are common in forested areas. Green Pigeons  feed largely on ripe figs, some more than others. The Thick-billed Green Pigeon  and the  Large Green Pigeon feed almost exclusively on the figs of canopy level stranglers and for that reason are highly nomadic.

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The 5  species of  Treron Green Pigeons partition their habitat by size. Only the Large Green Pigeon has a gape big enough to swallow large figs  such as Ficus dubia whole. All the green pigeons are seed predators.

In contrast the Imperial Pigeons illustrated below are all seed dispersers and do not predate fig seeds.0003 04b Imperial Pigeons Full DPS.jpg

Borneo’s largest pigeons are 4 species of Ducula Imperial Pigeons and two species of  Columba Wood Pigeons. The Green Imperial Pigeon Ducula aenea  is common in forested areas throughout Borneo and is one of the top fig seed dispersers in Borneo. All the rest of the pigeons illustrated above are now scarce or very rare

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Ducula Imperial pigeons  are very important seed dispersers. They swallow large figs whole and defecate the seeds thereby farming and enhancing their own habitat. In contrast  the 2 Columba Wood Pigeons are seed predators. Both Columba species are nomadic island specialists on the verge of extinction due to predation of their  nests  by fishermen and rats.

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The 5 doves  found in Borneo are all seed rather than fruit eaters. They will eat fig seeds opportunistically but only as a small part of their diet. This means that they are not serious fig seed predators

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Of the 5 pigeons illustrated above the top two Ptilinopus Fruit Doves are both fig specialists which swallow small figs whole and defecate the seeds. In contrast the  the feral Rock Dove and the Nicobar Pigeon are both seed predators which feed on the ground.

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Summary: Of the 21 pigeons that live in Borneo only 5 species (3 Ducula  Imperial Pigeons and 2 Ptilinopus fruit doves) are fig seed dispersers  which enhance or “farm” their habitat. The other 17 species are seed predators which effectively destroy their preferred habitat by predating the seeds of their most favored fruit.

Overall  Borneo’s  21 pigeons probably have a negative effect on fig populations.

The effect of this “pest pressure” on figs has led to a number of evolutionary adaptations by fig fruits to avoid seed predation;

  1. Many fig fruits are too large for  Treron Green Pigeons to swallow. See Ficus drupacea at Signal Hill 
  2.  Most fig seeds are too small  for most doves to bother  eating. See Ficus racemosa and Zebra Dove

All illustrations are by Karen Phillipps copied from the Phillipps’ Field Guide to the Birds of Borneo  Third edition (2014)