There are only two common strangling figs found on most offshore islands of Borneo, Ficus drupaceae and Ficus microcarpa.
Ficus drupacea figs are the favored food of Green Imperial Pigeons and Ficus microcarpa figs are the favored food of Pink-necked Green Pigeons.
Island figs are dispersed or predated by 9 different species of pigeons. On islands pigeons replace barbets and hornbills as the most important dispersers of figs. The habits of the 3 common generalist pigeons which regularly fly between the islands and the mainland are described in this article.
An additional 6 Borneo pigeons are island specialists and only rarely visit mainland Borneo. 3 of these are rare, fig seed predators. Another 3 are locally common fig seed dispersers.
Green Imperial Pigeon Ducula aenea feeding on Ficus drupacea on Signal Hill in the center of Kota Kinabalu, Sabah. These large pigeons fly regularly between Gaya Island and the islands of the Tunku Abdul Rahman Park and the secondary forest surrounding Kota Kinabalu to feed on fruiting figs. Green Imperial Pigeons defecate fig seeds intact and are therefore farming their own preferred food (figs) in their preferred habitat.
Their gape (size of open beak) is just large enough to swallow Ficus drupacea figs whole.
Pink-necked Green Pigeons also feed on Ficus drupacea figs, but their gape is not big enough to swallow these large figs whole. They have to wait until the figs are ripe and soft so that they can peck the figs open and swallow them piece by piece. Green Pigeons eat both the fig flesh and the seeds. Although some seeds are ground up in their gizzards it is likely that some seeds also escape intact.
The preferred fig of Pink -necked Green Pigeons is Ficus microcarpa because the pigeons gape size is big enough to swallow these F. microcarpa figs whole. This is a male photographed at Kent Ridge Park in Singapore.
Photo by JJ Harrison (https://tiny.jjharrison.com.au/t/2U6wKEr9CA93U7iF) – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=76303707
This is a female Pink-necked Green Pigeon photographed at Kent Ridge Park in Singapore feeding on Ficus microcarpa figs. Note the lumpy swollen crop of the pigeon filled with ripe figs.
Photo by JJ Harrison (https://tiny.jjharrison.com.au/t/2U6wKEr9CA93U7iF) – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=76303707
A Green Imperial Pigeon and a Pink-necked Green Pigeon feeding next to each other on ripening Ficus drupacea figs. Because Green Imperial Pigeons have a gape large enough to swallow Ficus drupacea figs whole they get first choice of the crop whilst the Pink-necked Green Pigeons only get the leftovers.
Emerald Doves Chalcophaps indica are seed predators of the small fallen seeds of a figs and secondary forest plants such as Macarangas and Mallotus species. They are night flying, long distance migrants often flying between islands and the mainland. They always feed on the ground.